Homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency revealed by stroke in adult sibling

Many genetic disorders result from an inborn error of metabolism. The patient lacks an important enzyme, and as a result critical biochemical reactions cannot take place. Some inborn errors of metabolism are quite common, but a deficiency in the enzyme 5,10-methylenetetrahydrofolate reductase is rare. The enzymatic defect results in the presence of large amounts of the amino acid homocysteine in the urine, a condition called homocystinuria. Although the condition is rare, it is quite serious. The mental development is retarded from early infancy and death often comes within a year. Three unusual patients have now been found, which suggests that the disorder may go unrecognized. All three patients were young adults in their early 20s when they had severe strokes. Investigation revealed that all three patients were retarded, but only mildly so. Imaging studies revealed abnormalities in all three patients and brain atrophy in two. The three patients were all from the same family, and a thorough biochemical analysis was performed revealing excessive homocysteine in the urine. The three patients were among six siblings in the family, and further investigation revealed that one additional sibling had no symptoms but nevertheless had high levels of homocysteine in her urine. Two of the three patients died within one year of diagnosis. These cases illustrate that homocystinuria need not always result in rapid death in infancy. Furthermore, the cases suggest that the enzymatic defect may contribute to blood vessel abnormalities, which lead to recurrent strokes in young adulthood. (Consumer Summary produced by Reliance Medical Information, Inc.)