High Myopia: A Pointer of an Inborn Error of Metabolism.

An 11-year-old boy with marfanoid habitus and high myopia presented with multiple episodes of seizures. He was found to have arachnodactyly, hypermobile joints, ectopia lentis, cerebral venous sinus thrombosis (CVST) with very high serum methionine and homocysteine. Genetic evaluation unveiled homocystinuria due to cystathionine beta-synthase deficiency. The patient was treated with high-dose pyridoxine, methionine restricted diet, anticonvulsants, warfarin, and correction of ectopia lentis. Homocystinuria should be suspected in patients with tall stature and pathological myopia. Early treatment can prevent thromboembolic complications.