When was achondroplasia dwarfism discovered

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Click on the link to view a sample search on this topic. Health Supervision for Children With Achondroplasia. Pediatrics ;; Have a question? References References. Genetics Home Reference. Pauli RM. Bacino CA. Learning About Achondroplasia. Defendi GL. Genetics of Achondroplasia. Medscape Reference.

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Support for Patients and Families. Tips for Finding Financial Aid. Help with Travel Costs. How to Get Involved in Research. Medical and Science Glossaries. Caring for Your Patient with a Rare Disease. FindZebra Diagnosis Assist Tool. Finding Funding Opportunities. Teaching Resources. Bowed legs Bowed lower limbs [ more ].

Nasal tip, upturned Upturned nasal tip Upturned nose Upturned nostrils [ more ]. Depressed bridge of nose Flat bridge of nose Flat nasal bridge Flat, nasal bridge Flattened nasal bridge Low nasal bridge Low nasal root [ more ].

Deafness Hearing defect [ more ]. Infantile muscular hypotonia. Decreased elbow extension Elbow limited extension Limitation of elbow extension Limited extension at elbows Limited forearm extension Restricted elbow extension [ more ].

Increased size of skull Large head Large head circumference [ more ]. Decreased length of bridge of nose Decreased length of nasal bridge Short bridge of nose [ more ].

Acanthosis nigricans. Small chest Small thorax [ more ]. Percent of people who have these symptoms is not available through HPO. Autosomal dominant inheritance. Conductive deafness Conductive hearing loss [ more ].

Outward bow-leggedness Outward bowing at knees [ more ]. Hunched back in infancy Round back in infancy [ more ]. Decreased size of midface Midface deficiency Underdevelopment of midface [ more ]. However, in practice such a trial is virtually impossible. Over the course of 30 years, the largest specialty clinics assess around unique individuals with achondroplasia [ 10 ]. Each such clinic, then, would identify only around 0.

Not only would a collaborative venture be needed, but even so only after many years would sufficient numbers be accumulated. The subarachnoid spaces are enlarged in most children with achondroplasia. Because of this increased extra-axial fluid, the bridging vessels which may also be distended because of obstruction at the jugular foramina may be especially susceptible to shearing trauma. Several instances of subdural hematoma formation in children with achondroplasia [ ] and personal observation following minimal trauma probably arose because of this increased susceptibility.

Such an occurrence should not be interpreted as necessarily implying that nonaccidental trauma has occurred. Although the risk for unexpected death secondary to craniocervical constriction nearly disappears after the first year of so of life [ 8 , , ], the foramen magnum remains small.

This results in a residual risk that an individual may experience spinal cord damage, either insidiously or acutely. That high cervical myelopathy develops in some individuals with achondroplasia has been recognized for a long time [ , , ]. Such cervical myelopathy can arise at any age [ ], although it seems more frequent in childhood — perhaps because of continued, albeit slow, growth of the chondrocranium with age [ ] or perhaps because precipitant trauma is more likely in children.

No estimate is available for level of risk. In young children clinical features that may suggest cervical myelopathy include long persisting hypotonia, asymmetric resistance and strength, asymmetric reflexes, ankle clonus, or upgoing response to Babinski stimulation [ 8 ].

After a child begins to ambulate, note may be made of classic features of cervical myelopathy [ ] including orthograde fatigability, decreased endurance, apparent sudden, transient pain in the arms or legs, decreased fine motor function or changes in bowel or bladder continence.

Alternatively, a child may present with acute, severe myelopathy secondary to injury [ ] which requires urgent neurosurgical involvement. Given risks related to craniocervical constriction, all individuals with achondroplasia must be managed as having a small foramen magnum and increased risk for trauma-based cord compression. It is crucial that parents be counseled about physical activities and sports activities that create unacceptable risk [ 1 , 4 ].

Activities that should be prohibited, or at least strongly discouraged, include: trampoline use; vaulting in gymnastics; diving off of diving boards; sparring in martial arts; American football; rugby; downhill skiing; heading in soccer, etc. On the other hand, many physical activities are reasonably safe and can be encouraged, such as: swimming; golf; tennis; basketball; soccer except for heading and only at younger ages, since competitive soccer becomes much more risky in older children ; baseball; softball.

If parents understand that what one is trying to do is limit activities that cause substantial risk for forceful head and neck injury, they usually can assess whether a particular endeavor is unsafe. Note that because what creates risk is violent neck movement, helmet use is not preventative. In younger children, continuing rear facing of the car seat for as long as tolerated is probably prudent. Safety precautions such as gated stairways are also especially important.

The only relevance of these findings probably is to document in medical records and to explain to the parents their presence, since they may be cause for undue concern in some circumstances. These were often associated with thinning of the cord in the same region [ ].

Although the origin of these lesions is unknown, it is conceivable that they reflect gliosis arising secondary to such temporally distant, minor cord injury [ ], which injury could be either direct compression or of vascular compressive origin. In contrast with some other bone dysplasias, atlanto-axial instability is exceedingly rare in achondroplasia with only a handful of cases reported in the literature [ , ]. It is so infrequently a concern that it probably does not need to be evaluated in any routine circumstance.

Although far more common in those with hypochondroplasia [ 77 ], seizures occasionally arise in those with achondroplasia [ , ]. In fact, paroxysmal events with apnea in infants with achondroplasia may arise from a variety of causes: secondary to abnormalities at the craniocervical junction and consequent abnormality of central respiratory control; from primary seizures; from airway obstruction related to macrocephaly and hypotonia e.

Particularly in infancy, distinguishing primary apnea from seizure-precipitated apneic events may be challenging. Temporal lobe dysgenesis is common in individuals with hypochondroplasia secondary to FGFR3 mutations [ 83 , 84 ].

Given that achondroplasia and hypochondroplasia belong to the same family of bone dysplasias [ 52 ], it would not be surprising to identify similar dysgenesis in occasional individuals with achondroplasia. In fact, that was recently reported by Manikkam et al. Nor has the frequency with which temporal lobe dysgenesis results in seizures, or whether temporal lobe abnormalities are a marker for more severe central nervous system consequences of FGFR3 been determined.

Both central apnea and restrictive breathing problems, which for the most part are exclusively issues in young infants, have already been addressed. In addition, children and adults with achondroplasia have an exceedingly high frequency of obstructive sleep apnea [ , , ]. Estimating the frequency with which people with achondroplasia have sleep apnea is challenging.

Obstructive sleep apnea may present at any age. In fact, there is a remarkably high rate of obstruction even in children less than 2 years of age [ ]. Not surprisingly, however, there is a dramatic increase as physiologic hypertrophy of the lymphatic ring — and particularly the adenoids — arises between around 2 and 10 years of age. Screening for possible obstructive apnea is challenging [ ].

Nonetheless, either a parent in children or a sleep partner in adults should be taught the features that suggest that clinically significant increased upper airway resistance is present. Likewise, most infants with achondroplasia perspire profusely and this is not indicative of any medical issue.

Features of significance in children include: neck hyperextension; loud and irregular snoring; glottal stops; observed apnea; deep, compensatory sighs; self-arousals; secondary enuresis; night-time emesis; morning headaches [ ] and personal observations.

Of these, Sisk et al. In older children, there may be change in school performance or changes in behavior, including new onset of distractibility and poor attention [ ].

In adults, there are daytime behavioral scales that can be used to query about symptomatic apnea [ ]. Parents need to be assured that obstructive apnea is almost never an acutely life threatening problem, but rather has long term effects that must be mitigated.

Consequences of sleep apnea are not markedly different in individuals with achondroplasia compared with the general population. As mentioned, in children there may be negative learning and behavioral consequences [ , ]. Because pulses of growth hormone secretion occur during sleep [ ], sleep disruption can negatively affect growth, independent of the primary diagnosis of achondroplasia.

In adults daytime symptoms arising from poor sleep quality at night markedly increase the risk of various kinds of accidents [ ]. Physiologic consequences can arise at any age. Particularly concerning are the cardiovascular consequences of long term sleep apnea [ ], which are observable in affected individuals with achondroplasia [ ]. Not only may obstruction resulting in recurrent and prolonged desaturations result in pulmonary hypertension and eventual cor pulmonale, but it may be a critical contributor to hypertension risk [ ].

In children, a number of factors conspire to make obstructive apnea far more likely. In everyone there is physiologic decreased muscular tone in sleep [ ] resulting, effectively, in smaller airway size.

In children with achondroplasia there is hypoplasia of the midface with consequent diminution of anatomical airway size [ , , ]. The anatomy of the face is predictive of likelihood of obstructive apnea in average children [ ] and in children with achondroplasia, too [ ] — the flatter and retruded the midface, the more likely that sleep apnea may develop. After around age 2 years there is physiologic hypertrophy of the lymphatic ring [ ]. These factors are likely the major contributors to pathogenesis of obstructive apnea in most children with achondroplasia.

Other factors may play a role in some. Centrally mediated obstruction as well as decreased respiratory effort may arise because of cranial base abnormality [ , ]. Gastroesophageal reflux is sometimes a critical contributor [ ]. Lower airway malacia tracheobronchomalacia has recently been recognized to be of substantial frequency in achondroplasia and does complicate the management of other factors resulting in obstruction [ ]. In adults, midfacial abnormality persists, while lymphatic obstruction is usually not significant.

The most critical additional factor in many adolescents and adults is the onset of obesity, a feature strongly related to sleep apnea [ ]. The first steps in assessment is to elicit observational history regarding all of the features discussed above under Clinical presentation.

General clinical assessment should include evaluation of severity of midface hypoplasia, degree of tonsillar hypertrophy and evidence for nares patency. In addition, contributing factors not unique to achondroplasia such as allergic rhinitis need to be ruled out. If concern is present, two approaches can be considered. Polysomnography will objectively document the presence of and severity of obstructive apnea and disordered breathing, and is often the first elected investigation [ 4 , , ].

In children with severe and unequivocal historical symptoms, alternatively one might choose to have otolaryngologic evaluation including nasopharyngoscopy [ ] completed. The latter approach, however, while allowing more rapid initiation of intervention if needed, does not provide objective data against which post-treatment studies can be compared.

When serious obstructive abnormalities are demonstrated by polysomnography, then referral should be made to a pediatric otolaryngologist for evaluation. Stepwise management of obstruction in children typically begins with adenoidectomy with or without tonsillectomy.

Although one would expect that adenoidectomy along would usually suffice, outcome appears to be better in those who undergo tonsillectomy as well [ ]. Children with achondroplasia may have an increased risk for post-operative complications [ ] and probably should be hospitalized overnight following any procedure requiring intubation. While a majority will show marked improvement after surgical intervention [ ] nevertheless polysomnography should be completed a few weeks after surgical intervention, since in many individuals obstruction persists at a level requiring additional treatment [ ].

In those in whom additional treatment is needed, step two is the use of positive airway pressure cpap, bipap. Positive airway pressure treatment is effective in those with achondroplasia [ , ], including in very young children personal observation. In a large majority, those interventions are sufficient to correct the obstructive apnea and prevent sequelae. Rarely additional treatment may be needed.

Uvulopharyngopalatoplasty [ ] has occasionally been done, but the numbers are so small that benefit is difficult to assess. Rare individuals may require temporary tracheostomy personal observation , although this is more likely to be needed for restrictive disease in infancy than because of inability to otherwise treat obstructive apnea.

Occasionally surgery has been done to correct the midfacial hypoplasia, when severe, by either midface advancement [ ] or distraction [ , ]. In adults, most often positive airway pressure treatment is the primary and most important intervention.

If appropriate, it needs to be accompanied by efforts at weight loss. The role of surgery in adults with obstructive apnea is unclear. Middle ear dysfunction is exceedingly common in both children and adults with achondroplasia. This presumably is so because of poor functioning of abnormally oriented Eustachian tubes, which abnormality, in turn, arises because of aberrant growth of the chondrocranium [ ].

A number of studies have assessed middle ear function and hearing in achondroplasia. All are limited, because of sample size e. Glass et al. Hunter et al. Tunkel et al. A well-designed, prospective study is very much needed. Nonetheless, currently available information provides a reasonably clear picture of middle ear issue5s in achondroplasia. In a large, cross-sectional study of a convenience sample, Tunkel et al.

This issue is not solely one of childhood [ ], although greatest concern is appropriately centered on the period of language acquisition in early childhood, during which hearing loss can be a major factor contributing to speech and language delays. A high level of suspicion of possible hearing loss is appropriate at all ages. Formal behavioral hearing assessment and tympanometry should be completed by around 1 year of age [ 1 ]. These should be repeated at least yearly at least until school age [ 1 , ].

Because medical management of middle ear dysfunction is usually ineffectual [ 4 ], pressure equalizing tube placement is usually appropriate.

Once need is demonstrated, tubes will usually be needed at least until 7—8 years of age [ 4 ]. There is an increase in the occurrence of jugular bulb dehiscence into the middle ear space [ , ] again because of abnormality of the chondrocranium. This can sometimes causes persistent, unilateral hearing loss [ ]. Occasionally is can cause unexpected, brisk bleeding from myringotomy if not recognized before surgery [ ].

When hearing loss is documented in childhood, standard approaches to habilitation are appropriate. These include parental awareness, preferential seating in school, use of environmental amplification if needed, etc. In only a few children are hearing aids warranted. However, note should be made of the remarkably high frequency of hearing loss in adults and, as well, the remarkably low frequency of hearing aid use in them [ ].

It is likely that many adults would benefit from amplification. That most infants with achondroplasia develop a transient kyphosis has been recognized for nearly a century [ , , ]. In fact, nearly every infant with achondroplasia under a year of age has a kyphosis at the thoracolumbar junction [ 64 , ] Fig.

This is a non-congenital deformity unassociated with any primary structural defect of the vertebrae Fig. It usually becomes more obvious with the onset of sitting. Lateral radiograph of the spine of an infant with achondroplasia. While there is obvious kyphosis, there are no secondary changes of the vertebral bodies at the apex of the curve.

Severe, fixed angular kyphosis of the type that can be prevented by appropriate counseling and intervention in early childhood. J Pediatr Orthop — [ 64 ]. Wedging or beaking of vertebrae at the apex of the curve with loss of substance of the anterior vertebral body is indicative of the beginning of fixation of the curve [ 64 , ] Fig. However, neither development of such beaking, nor progression to a fixed curve is inevitable. Cross table supine over-a-bolster lateral radiograph shows a mild irreversible kyphotic curve and mild loss of anterior substance of two vertebrae.

This view or, alternatively, a cross table prone lateral radiograph, can be used to assess the irreversible component of kyphotic curvature. That progression arises from deleterious effects of gravity acting at a disadvantageous angle because of positioning of the infant was first suggested by Beighton and Bathfield [ ].

We suggested that a biophysical explanation of progression was likely secondary to a number of nearly uniform features in infants with achondroplasia: hypotonia; macrocephaly; generalized ligamentous laxity. These features mean that when placed in a sitting position, a slumped, C-sitting posture will arise, which can lead to anomalous gravitational forces causing remodeling of an intrinsically abnormal spine [ 64 ].

If that mechanism is true, then prohibition of unsupported sitting and other strategies to decrease the time spent with gravity exerting disadvantageous force should decrease the likelihood for kyphosis to progress [ ].

A descriptive guide for parents is available from the author on request or online at the Little People of America website. A protocol has been developed that can act as a guide to the prevention of fixed kyphosis Fig.

Others have more recently confirmed the benefit of such behavioral strategies, as well as demonstrating that those with more severe motor delays presumably because of more severe hypotonia are more likely to have persisting kyphotic curves [ ].

It is for that reason that we developed treatment for those in whom more than a mild, fixed component of the kyphotic curve develops with a modified thoracolumbosacral orthosis TLSO. A descriptive guide for physicians and orthotists is also available from the sources cited above.

With use of such a protocol very few children should have need for surgical intervention although, admittedly, compliance with bracing is challenging for some families. In only one of more than children managed in this manner did recurrence of a clinically significant curve arise after following such a protocol personal observation. Similarly, Xu et al. Suggested algorithm for the assessment and management of kyphosis in infants and young children with achondroplasia. In those individuals who were not counseled regarding preventive strategies, or in whom prevention and bracing fails, surgery is appropriate [ , , ].

The aims of surgery are to reduce the severity of the curve, decompress the spine and stabilize it [ ]. Spinal arthrodesis with instrumentation seems to be the most effective approach [ ], although, of course nothing approaching a controlled study regarding alternative options has been published.

Most children develop an exaggerated lumbar lordotic curve sway back when they begin to stand and walk Fig. They should be reassured that this is a normal characteristic of children with achondroplasia.

Lateral radiograph of the lumbar and sacral spine. It shows the horizontal sacrum and marked hyperlordosis often seen in those with achondroplasia. Hyperlordosis is usually asymptomatic and requires no treatment.

When marked, there may be an increased incidence of pain at the apex of the curve. When marked, it may also increase the likelihood for intermittent spinal claudication or symptomatic spinal stenosis in adolescents and adults see below [ , ].

Because it may result in a fully horizontal sacrum Fig. Severe hyperlordosis may be diminished in severity by a physical therapeutic exercise program — low back and lower abdominal muscle strengthening and pelvic rotations personal observation. All individuals with achondroplasia have substantially diminished caliber of the spinal canal along its entire length [ , ]. A combination of factors contribute to this and to foraminal narrowing.

The spine shows decreased interpediculate distances, short and thick pedicles, and many affected individuals have some degree of thoracic kyphosis and lumbar hyperlordosis. The latter two features may make symptomatic spinal stenosis more likely [ ]. For the most part, issues arising from the anatomic lumbosacral stenosis are problems of late adolescence and adulthood, with average age of symptoms onset in the 4th decade [ , ].

Likely, this is because with age secondary problems, such as arthritis, disk disease, etc. Earliest symptoms typically are back pain and buttock pain, with gradual distalward progression of discomfort [ , ].

It is important to distinguish between intermittent spinal claudication [ ] and potentially irreversible symptomatic spinal stenosis, a distinction that is often not made in the surgical literature. Exercise induced intermittent spinal claudication neurogenic claudication is a disorder of the elderly in the general population [ ].

In contrast, it commonly arises in older children and young adults in those with achondroplasia. Critical in its differentiation from bony compressive changes in the spine, claudication arises with orthograde activities and resolves often quite quickly with rest.

Symptoms may include exercise induced tingling, numbness, pins and needles, pain, or a heavy feeling in the legs. Stopping the precipitating activity standing, walking, running results in resolution in seconds or minutes. Often persons with achondroplasia find that more rapid relief arises with squatting personal observation.

With careful questioning, a majority of adults report some of these features, but many seek assessment only if walking limitations become marked. Neurogenic claudication probably arises because of vascular congestion that is increased by blood flow changes associated with exercise and which results in transient nerve root ischemia [ ].

As such a mechanism implies, neurogenic claudication results in no permanent damage to the cord or nerve roots. Therefore it generally can be treated non-operatively. No studies have adequately assessed non-operative treatments in the general population [ ], and their effectiveness in those with achondroplasia is utterly unexamined. Things seemingly of benefit include weight loss in the overweight and obese, low back physical therapy, and efforts to decrease the severity of hyperlordosis through an exercise program.

Because no harm will accrue from physical activity, patients should be encouraged to continue to walk and otherwise exercise. Only if spinal claudication causes marked compromise of physical ability and of quality of life should surgery be considered.

A smaller proportion of individuals develop more serious symptoms for which surgical intervention should be more often considered. Bony compression can be of nerve roots or the cord and cauda equina. Signs and symptoms that do not abate with rest suggest that problematic stenosis is developing.

Features of particular importance include persistent leg weakness, clumsiness, changes in gait, and development of bladder or bowel incontinence [ ]. Such symptoms and signs should precipitate neuroimaging. However, every person with achondroplasia will have spinal stenosis [ ], and that in itself should not be seen as justification for surgical intervention. Furthermore, imaging is remarkably insensitive and nonspecific in assessing spinal stenosis [ ]. What imaging can do is identify what levels are most severely anatomically affected, and what additional factors likely precipitated the clinical deterioration.

Such documentation is critical when surgery is considered. Generally, surgical treatment involves extensive and wide posterior laminectomy [ , ]. Given that virtually all studies regarding operative intervention are retrospective and are subject to ascertainment biases, recall biases, incomplete follow-up and so forth, all conclusions about surgery remain subject to debate and will continue to be so until and if prospective, controlled studies are carried out.

Tentative conclusions include the following. While lumbosacral spinal stenosis may occasionally require surgery in childhood [ , ], more often surgery is carried out in the 4th and 5th decades [ , ]. How quickly after onset of symptoms surgery should be done versus a trial of non-operative interventions including physical therapy [ ] is controversial [ ], with some data supporting aggressive operative intervention soon after onset of symptoms [ ].

Improvements following laminectomy do generally arise [ ]. As in the general population [ ], there is less apparent benefit with time post-surgery, with Pyeritz et al. As in the wrists and hips, most children with achondroplasia have excess mobility of the knees.

Although this feature is usually insufficient to cause major symptoms or require surgery [ ], rarely there is overt tibiofemoral subluxability personal observation , which is one of the few circumstances in which transient bracing of the knee in a child with achondroplasia may be appropriate. Mediolateral instability is nearly uniformly present in young children with achondroplasia.

This often seems to contribute to focal pain precipitated by orthograde physical activity personal observation. Usually it lessens with age, disappears by adulthood, and rarely, in itself, requires any intervention other than non-specific treatments for pain rest, warmth, massage and nonsteroidal anti-inflammatories. Lateral instability may be an integral part of the bowing deformity that is often present in those with achondroplasia, both contributing to this problem and responding to its treatment.

Bowing of the legs is a normal feature of average statured children in the first 2 years of life [ ]. This is in contrast to what is seen in achondroplasia. In the child with achondroplasia there is often inexorable, continued progression of varus deformity. The severity of bowing is often asymmetric [ , ]. There is some suggestion that males may be more often affected with clinically relevant bowing than are females [ ].

Rather, there is usually lateral, dynamic instability of the knee, varus of the tibia, internal tibial torsion and tibia recurvatum [ ]. The complexity of the dynamic deformity is well illustrated using gait analysis [ ]. In contrast, arthritis does not seem to be common in adults with achondroplasia [ ], although no substantive study has been done to confirm this. Symptoms that arise most frequently include activity-precipitated pain and self-limitation of walking and other orthograde physical activities [ ].

Clinical assessment should include asking about activity induced discomfort or pain. Often children will report pain particularly after physically busy days with onset in the afternoon, evening or awakening them from sleep. Measurements of distances between the knees, mid-tibiae and medial malleoli Fig. Measurement of thigh-foot angle Fig. Methods that can be used to monitor progression of varus deformity without repeated radiologic studies which, however, are needed if the bowing is sufficiently severe that intervention is being considered.

In addition, in those in whom there is concern about the severity of bowing or who have serious symptoms referable to bowing, radiographic evaluation should be done. Most helpful is a standing, full leg length image with the patellae pointing forward irrespective of the resultant foot position [ ].

Other assessments that have been used by some include arthrography [ ], magnetic resonance imaging of the knee [ ], and gait analysis [ ]. There is no consensus about the relative importance of a number of factors that may contribute to the complex varus deformity of achondroplasia. That is unfortunate, since strategies for intervention are at least in part predicated on assumptions about mechanism. Bowing probably is two discrete processes.

In young children the varus deformity is usually primarily proximal — just distal to the knee, while in adolescents varus tends to develop just above the ankle [ ]. In young children factors that have been suggested as being important include fibular overgrowth [ ], lax lateral collateral ligaments [ , ], as well as true deformity of the tibia. The relative contribution of each of these and how they interact [ ] has yielded conflicting evidence.

For example, while Ain et al. Absent clear association, and most certainly absent any evidence that fibular overgrowth is actually a primary cause of leg bowing, there is little to suggest that primary surgery on the fibula is likely to be effective. In those in whom any of the following features are present, surgery should be considered: three weight bearing joints out of plumb; persistent lateral knee pain not relieved by conservative measures; development of a lateral thrust [ ].

Standard surgery is a valgus producing and derotational osteotomy of the proximal tibia as well as some method to shorten the fibula in order to effectively tighten the lax lateral collateral ligament [ , ]. Obviously, intervention is tailored to the evaluative findings in a particular child; some may require multi-level osteotomies; in some older children distal tibial osteotomy is appropriate [ ].

All such surgery has risk for substantial complications such as infection, malunion, compartment syndrome, peroneal palsy, and need for additional surgery because of recurrence [ ]. Alternatives have been suggested in the past but not enthusiastically embraced currently. It was suggested that proximal fibular epiphyseodesis could be a simple surgical way to prevent development of bowing [ ].

Of course this assumes that fibular overgrowth is the primary pathogenetic precipitant of bowing. Partial fibulectomy alone has also been considered [ ]. This would, presumably, both decrease the tension of the fibula and tighten the lateral collateral ligament. There seems to be no literature suggesting that direct operative treatment of the lax lateral collateral ligament is a reasonable option. Its role in treating varus deformity in achondroplasia is currently unsettled.

On the surface, use of 8-plates appears to be illogical since one might expect that they would only correct one dimension of the complex deformity that it usually present. Certainly, given the slow rate of growth in bone dysplasias, correction will be far slower and symptoms will not be relieved for the time needed for correction. Nonetheless, impressive outcomes have been demonstrated P. Stevens, personal communication Limited published data regarding its use in those with achondroplasia [ ] suggest that at least partial correction of malalignment can be accomplished.

There even is anecdotal evidence that correction in one plane varus deformity will secondarily results in improvement of the other components internal torsion and lateral instability P. Whether this surgically far simpler and far less debilitating option is a good alternative remains uncertain. Treatment of bowlegs in achondroplasia is a good example of the many unknowns that remain. For example, questions that have not been adequately addressed to date include:. What is the prevalence of knee osteoarthritis in adults with achondroplasia, and does it correlate with the severity of varus deformity?

Recent animal studies suggest that activation of FGFR3 may confer protection against development of osteoarthritis [ , ]. If this is true in humans as well, then those with achondroplasia may tolerate more severe bowing without debilitating secondary arthritis than is the case in the general population.

The availability of imaging techniques — particularly magnetic resonance imaging and direct visualization by arthroscopy — has resulted in recognition of a number of anatomic variants of the knee in achondroplasia [ , ]. Of these, the finding likely of greatest significance is an exceedingly high prevalence of discoid lateral menisci.

Although relatively common in the general population [ ], there seems to be a much higher prevalence in children and adolescents with achondroplasia who present with knee pain. There are a host of causes for knee pain in this population, the most common of which is varus deformity. A discoid lateral meniscus, which may predispose to meniscal injury [ , ], should be considered particularly in those with lateral joint line pain and tenderness [ , , ]. Unfortunately, to date the data related to discoid lateral meniscus suffer from the usual problems — small series, ascertainment biases, uncontrolled interventions, etc.

However, that treatment of torn discoid lateral menisci does seem to result in symptom resolution suggests that this may, in fact, be another cause of knee pain in children and adolescents with achondroplasia. Shoulder hypermobility is virtually constant in individuals with achondroplasia [ ] and personal observation. This evidently arises because of unusual shape of the humeral head so that anteroinferior subluxability out of the glenoid fossa may occur, but, while subluxability is common, pain because of this instability is rare [ ].

Nonetheless it is probably prudent to limit the frequency of induced subluxation. Two activities and likely others with similar dynamics seem to particularly precipitate subluxation — butterfly stroke in swimming and dead-lifting of weights personal observations. Therefore, in those with clinically demonstrably unstable shoulders anteroinferior subluxability, apprehension sign those activities should be avoided.

Increasing subluxability has also been noted during humeral lengthening [ ]. In contrast to nearly all other joints, the elbows are stiff in those with achondroplasia.

Most individuals develop limitation of elbow extension beginning in childhood [ ]. This results in effective shortening of the arms even more, and limits reach accordingly. In the minority in whom radial head dislocation arises, even greater functional consequences will result, since not only will reach be diminished, but pronation and supination will also be limited although this can in part be compensated for because of excess mobility at the wrists.

Nevertheless, surgical treatment is almost never appropriate, unless humeral lengthening is elected because of reaching problems. Such reaching problems often can be addressed by using various adaptive devices see section Adaptive needs , Nonetheless, humeral lengthening as part of general extended limb lengthening or alone to treat issues related to reach limits and adaptive needs has been carried out in a large number of individuals with achondroplasia [ ]. This may be necessary in order to assure independence for perineal hygiene, particularly in those who have limitation of trunk mobility e.

Although modest, this may be sufficient to allow for greater independence for personal hygiene. The wrists in almost all children and in some adults are hypermobile [ ] Fig. Some of those with hypermobility demonstrate marked dorsoventral instability personal observation , which seems to correlate with functional difficulties related to wrist stabilization. Excess wrist movement and the need to stabilize the wrist for fine motor tasks can cause a number of problems.

Some children complain of fatigability after very short periods of writing; others have difficulty generating sufficient pressure to even make marks with a pencil. A number of options have proven to be beneficial see below under Adaptive needs. Surgery is never appropriate.

Because of hypoplasia of midfacial structures [ ] malocclusion is common. In addition to maxillary hypoplasia, there is relative overgrowth of the mandible; it is uncertain whether mandibular growth is itself normal [ ] or diminished [ ] but less so than is the diminishment of maxillary growth. Given these features, one might expect an extensive literature concerning management of malocclusions in those with achondroplasia; it is surprising how little literature concerning this is available [ , , , , , ].

Most children with achondroplasia will benefit from orthodontic care. Primary problems that are most often seen include marked narrowing of the anterior palate, with palisading of the upper incisors Fig.

Genetics Achondroplasia is a single gene disorder caused by mutations in the FGFR3 gene on chromosome 4. Two different mutations in the FGFR3 gene cause more than 99 per cent of cases of achondroplasia. It is a dominant genetic disease so only one copy of the FGFR3 gene needs to be mutated for symptoms to develop. Achondroplasia can be inherited from a parent with the disease.

However, most cases of achondroplasia are the result of a new mutation in the FGFR3 gene, over 80 per cent of people with achondroplasia have parents who are unaffected. Fibroblasts are cells that make the collagen and other structural materials in our tissues and bones. They also play an important role in wound healing. A growth factor is a protein that stimulates cell growth.

A receptor is a molecule on the surface of cells that binds with other molecules outside of the cell. This enables the cell to respond to external stimuli such as growth factors. The FGFR3 protein spans the cell membrane so that one end is inside the cell and the other is outside.

This allows the protein to interact with growth factors outside the cell and receive signals for growth and development. FGFR3 protein in bone cells helps control bone growth by limiting a process called ossification, which controls the formation of bone from cartilage. The bones of embryos are made largely of cartilage, so they are soft. Ossification uses calcium to create hard, strong bone, as the child grows.

This results in the FGFR3 protein being absent or damaged so that it cannot interact with external growth factors and therefore cannot control ossification. This results in problems during bone development where cartilage fails to turn into bone. Symptoms Due to poor bone development, the bones are shortened, particularly in the thigh and upper arms, a condition known as rhizomelia.

The thigh and upper arms are more affected because they have longer bones and larger growth plates regions of the bones where growth occurs.