HEREDITARY METABOLIC DISORDERS

HEPATOLENTICULAR DEGENERATION (Wilson's Disease)

This rare autosomal recessive disease of young adults-characterized by abnormal copper metabolism-causes changes in the basal nuclei, cirrhosis of the liver, and a pathognomonic corneal pigmentation called the Kayser-Fleischer ring. The ring appears as a green or brown band peripherally and deep in the stroma near Descemet's membrane and may only be visible with a slitlamp. The disease is progressive and often results in death by age 40. Treatment with penicillamine has resulted in sustained clinical improvement in some cases.

CYSTINOSIS

This rare autosomal recessive derangement of amino acid metabolism causes widespread deposition of cystine crystals throughout the body. Dwarfism, nephropathy, and death in childhood from renal failure are the rule. Cystine crystals can be readily seen in the conjunctiva and cornea, where fine particles are seen predominantly in the outer third of the corneal stroma.

There is no treatment.

ALBINISM

Oculocutaneous albinism consists of a heterogeneous group of conditions characterized by generalized reduction in or absence of melanin pigmentation and inherited as autosomal recessive traits. Mutations have been found on chromosomes 9, 11, and 15. At birth there is little or no cutaneous pigmentation, such that the skin and hair, including the eyebrows and eyelashes, are white or paler than expected. In severely affected cases this situation persists throughout life, whereas in less affected individuals some pigmentation and tanning with sun exposure can develop during childhood. The ocular manifestations are reduced visual acuity (generally 20/200), nystagmus, pale irides that transilluminate, hypopigmented fundi, and hypoplastic foveas. Photophobia is a prominent symptom. Ocular albinism, an X-linked recessive trait, has the same ocular features as oculocutaneous albinism but generally without cutaneous manifestations, though the skin may be paler than that of first-degree relatives. It is an important cause of congenital nystagmus. Female carriers may be identified by the presence of iris transillumination and retinal abnormalities. In all types of albinism there is a characteristic increase in the proportion of decussating axons in the optic chiasm, which can be identified by electrodiagnostic testing.

GALACTOSEMIA

Galactosemia is a rare autosomal recessive disorder of carbohydrate metabolism clinically manifested soon after birth by feeding problems, vomiting, diarrhea, abdominal distention, hepatomegaly, jaundice, ascites, cataracts, mental retardation, and elevated blood and urine galactose levels. Dietary exclusion of milk and all foods containing galactose and lactose for the first 3 years of life will prevent the clinical manifestations and will result in improvement of existing abnormalities. Even the cataract changes, which are characterized by vacuoles of the cortex, are reversible in the early stage.

Identification of the carrier state is possible by finding a 50% reduction of galactose 6-phosphatase.

10.1036/1535-8860.ch15

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