Microphthalmia, Syndromic 3
Patient Information
Characteristics
Background and History
In rare cases the eye does not grow to its normal size during embryological development, leading to a condition called microphthalmia. Sometimes there is only malformed eye tissue present and when no actual eye is visible it is called clinical anophthalmia. Even more rarely, the eye tissue fails to develop at all but this is associated with other brain maldevelopment which is usually incompatible with life. In many disorders such as this one, other body malformations are present.
Clinical Correlations
In addition to small or even absent eyes there are often abnormalities of the genitals and of the esophagus (swallowing tube). The small eye may be malformed and in some cases when the eyes appear to be absent, the optic nerve is missing and other brain malformations are present. The esophagus may fail to develop full and sometimes has an opening into the trachea (breathing tube). The palate may be split, the vertebrae do not develop normally, and the heart may have defects. Growth may be slow and psychomotor delays can occur. However, intellectual development and function is normal in other patients. The penis is often small and the testes may fail to descend properly.
Genetics
Inheritance
Based on genetic evidence, this seems to be an autosomal dominant condition in which an affected parent has a 50% chance of passing the gene mutation to each child. In some patients instead of a simple molecular change there is a major DNA change as evident from damage to a chromosome. Many cases occur sporadically, i.e., with no family history of similar disease.
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
Diagnosis and Prognosis
Ophthalmologists and pediatricians should collaborate in establishing the diagnosis. Depending on the severeity of the malformations, some patients live a normal life. However, others with severe abnormalities may die in infancy. Hearing and vision should be tested early and appropriate assistive devices used. Some defects such as those of the palate, heart, and esophagus may be surgically corrected. No treatment is available for the eye malformations and some patients are blind.
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