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Dermatologic Manifestations of Homocystinuria

Background

Homocystinuria is an inherited autosomal recessive defect in methionine metabolism that is caused by a deficiency in cystathionine synthase.
 This defect leads to a multisystemic disorder of the connective tissue, muscles, CNS, and cardiovascular system. Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of homocysteine in the serum and an increased excretion of homocysteine in the urine. Note the figure below.

Simplified picture showing homocysteine involvemen

Simplified picture showing homocysteine involvement in different metabolic pathways, as well as the role of vitamins B-6, B-12, and folate as a co-factors in this pathway.

In 1960, the first case of homocystinuria was reported from Northern Ireland. The patient was initially described as having an unusual case of Marfan syndrome with renal abnormalities at age 7 years. He had recovered from acute glomerulonephritis at age 6 years and was found to be hypertensive the following year. The patient was mentally slow and thin and had fair hair, pale skin, and flushed cheeks. He had arachnodactyly, dolichostenomelia, pes cavus, a high arched palate, and bilaterally dislocated lenses. At age 10 years, the patient’s urine was found to contain a large quantity of homocysteine; urinalysis results for the nitroprusside cyanide test were positive. The boy’s left eye was enucleated because of a staphylococcal infection that occurred after acute pupillary-block glaucoma developed. His right lens became dislocated into the anterior chamber and had to be removed.

The patient’s blood pressure readings normalized after his left kidney was removed when he was aged 13 years. Thick-walled internal arteries were noted at histologic examination. When pyridoxine supplementation was initiated at age 18 years, the patient’s plasma homocysteine levels decreased below the reference range. Daily folic acid supplementation was added 1 year later because his plasma folate level was low. At age 20 years, the patient had a perforated duodenal ulcer. Chest pain occurred at age 27 years and recurred at age 34 years. The chest pain was considered to be angina and was successfully treated. At age 50 years, the patient’s plasma homocysteine levels still remained low. The patient developed acute gout, which responded to indomethacin therapy.

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