Plummeting lenses in the TB clinic

In B6-independent forms, recycling to methionine is attenuated.1 Homocystinuria has often been found in people of European origin,2 and mutations in the CBS gene have been found in Brazilians of African descent.3 We have found only one previous report of homocystinuria from Africa; also compatible with autosomal recessive. inheritance.4 Isoniazid inhibits phosphorylation of pyridoxine,5 and pyridoxine is included in some tuberculosis treatment regimens to reduce the risk of isoniazid-induced neuropathy. The dramatic progression of ocular changes in our patient was probably precipitated by a rise in homocysteine levels caused by isoniazid therapy. Excess homocysteine is thought to react with cysteine residues, thereby disrupting the structure and function of fibrillin-1, the main component of the lens zonules (suspensory ligaments), leading to subluxation of the lens.