Stickler syndrome- type 3
Overview
Stickler Syndrome, type III: A rare genetic disorder characterized by joint problems, distinctive facial characteristics and ear abnormalities. Type 3 is caused by a genetic defect on chromosome 6q21.3. Type 3 doesn't involve any of the eye problems that occur in type 1 and 2.
Symptoms
* Flat face * Depressed nasal bridge * Prominent eyes * Epicanthal folds * Short nose * Anteverted nostrils * Underdeveloped mid face * Underdeveloped jaw * Cleft soft palate * Cleft hard palate * Cleft uvula * Deafness * Sensorineural deafness * Conductive deafness * Dental anomalies * Reduced muscle tone * Hyperextensible joints * Clubfeet * Prominent large joints * Severe joint disease * Joint pain * Partial dislocation of hip * Spondyloepiphyseal dysplasia * Flat vertebrae * Underdevelopment of distal tibial epiphyses * Flat irregular femoral epiphyses * Narrow shafts in long bones * Secondary degeneration of joint surfaces * Mitral valve prolapse * Long philtrum * Glossoptosis * Pectus carinatum * Long thin fingers * Elongated extremities * Reduced subcutaneous fat * Heart defect * Mental retardation * Displacement of the larynx
Causes
At least 19 different types of collagen have been identified. Collagen is an essential component of connective tissues. The collagen defect in most families with Stickler's syndrome is caused by a mutation in the type II collagen gene (COL2AI) located on chromosome l2q13. Other families demonstrate linkage to the COLIIA2 gene located on chromosome 6p2l.3 and others to the COLIJAI gene located on chromosome lp2l. COL2AI and COLIJA I are expressed in the hyaline cartilage, vitreous, intervertebral disc, and inner ear. COLIIA2 isn't expressed in the vitreous. Genetic studies have identified a few families who carry the clinical diagnosis of Stickler's syndrome yet don't demonstrate linkage to any of the three aforementioned collagen genes, suggesting further genetic heterogeneity (a pattern of traits caused by genetic factors in some cases and nongenetic factors in others). Approximately 1 in 10,000 people is affected with Stickler's syndrome. However, this incidence rate is considered conservative because persons with very mild symptoms may never be diagnosed with the syndrome.
Treatment
Beginning with the first 6 months of life, annual ophthalmology evaluation must be obtained to assess for myopia, vitreal abnormalities, and retinal degeneration and detachment. Persons who experience floaters or shadows in their vision require immediate assessment. Persons with vitreoretinal degeneration need to avoid contact sports and other physical activity that can jar and detach the retina. An auditory brain stem–evoked response evaluation should be done during the first month of life. The schedule for regular follow-up needs to be determined based on the results of the initial evaluation, frequency of otitis media episodes, and progress in language development. Early use of corrective lenses and hearing aids is recommended to enable developmental progression at the infant or young child's full potential. Depending on the infant's weight and health, surgical correction of the cleft palate can occur around age 9 months. With few exceptions, surgical closure of the palate should occur before age 2 in order to maximize speech and language development.