OMIM ID:
Sorsby Macular Coloboma Syndrome
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Macular colobomas, usually bilateral, are the major ocular feature of this oculoskeletal disorder. These are non-progressive and are generally heavily pigmented. Vision is, of course, severely reduced (20/200) and horizontal or pendular nystagmus is a feature in some cases.
Systemic Features
The systemic features are primarily skeletal. Patients have short-limbed dwarfism and brachydactyly of the type B variety. The thumbs and sometimes the large toes may be broad and bifid. The distal two phalanges sometimes short, absent, or duplicated and the nails can be dysplastic or absent. Syndactyly of several digits in both hands and feet is common. The ears are large and protuberant and some patients have deafness. Oligodontia may be present. Cartilage can have diastrophic changes. Mental development is normal.
Genetics
Inheritance
In the few families reported, the transmission pattern is vertical suggesting autosomal dominant inheritance but no mutation or locus has been reported. The mutation causing brachydactyly type B1 was not present in several cases.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission