OMIM ID:
Oculocerebral Syndrome with Hypopigmentation
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Patients have severe ocular malformations which so far lack full characterization. Nearly complete scleralization of the cornea prevents internal evaluation in most cases. There may be extensive neovascularization of corneal clouding. Anterior synechiae and cataracts have been described. Other patients presumed to have the same disorder have normal fundi or diffuse pigmentary changes. No limbal landmarks can be seen. The central cornea can be more transparent but no iris can be visualized. The eyes are microphthalmic as well. Slow, wandering eye movements are constant. Spastic ectropion of the lower lids is present. Lashes and eyebrows have minimal pigmentation and like the scalp hair have a slight yellowish tinge. There is no response to bright light in severe cases whereas in other more mildly affected individuals presumed to have this disorder there is only hypoplasia of the fovea with diffuse retinal pigmentary changes.
Systemic Features
Individuals have severe mental retardation from birth and never respond to environmental cues beyond having a marked startle response to auditory stimuli. Grasp and sucking responses persist at least into the second decade. The developmental delay persists from birth and patients never achieve normal milestones. Athetoid, writhing movements are prominent. The limbs are spastic, and deep tendon reflexes are hyperactive. Contractures are common. Hypodontia, diastema, and gingival hyperplasia are usually present and the hard palate is highly arched. The skin is hypopigmented but pigmented nevi may be present and the distribution of melanocytes is uneven microscopically. Cerebellar hypoplasia has been reported in some patients.
Genetics
Inheritance
This is a presumed autosomal recessive disorder based on its familial occurrence and parental consanguinity in some families. An interstitial deletion [del(3)(q27.1-1q29)] has been identified in the paternal chromosome of a 4-year-old female but the molecular defect remains unknown.
Clinically heterogeneous cases from Africa, Germany, Italy, Great Britain, and Belgium may not all have the same disorder and evidence for a distinctive phenotype remains elusive.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.