A case series of Pyridoxine Resistant Classical Homocystinuria

Homocystinuria is an autosomal recessive disorder with the prevalence of 1;200000. It is due to the defect in the Methionine metabolism which results in accumulation of Homocysteine in the body. We report a series of patients with Homocystinuria followed up at university paediatric clinic Teaching Hospital Karapitiya. There were four children with Homocystinuria from 7 to 18 years, of them, 2 were males. None of them were born to consanguineous parents and two were siblings. The age at diagnosis ranged between 6 to 17 years. All children had delayed cognitive development with the IQ level between 40-77. The condition was suspected with the onset of opthalmic manifestations such as Ectopia lentis glaucoma and ptosis. Marfanoid body habitus (tall stature, high arch palate and arachnodactyly) and scoliosis were present in all four children. Three children had low bone mineral density and 2 of them had fractures. None of them had thromboembolic events. Serum Homocysteine and Methionine levels were high, ranged 145-373μmol/L (4.6-8.1) and 79-177 μmol/L (6-60) respectively. All had normal vitamin B12 levels between 150.0 and 216.0 pmol/L (140-650). It is well known that early detection and initiation of treatment would prevent most of the complications in Homocystinuria. However, in this case series, all children were diagnosed later. Therefore, it is important to suspect the condition in children with intellectual impairment, visual defects and marfanoid body habitus.