A Case of Homocystinuria Missed by the Newborn Screening

Abstract

Blood methionine concentration has been monitored for the screening of homocystinuria at the neonatal period. Urinary homocystine must be identified for confirmation of the diagnosis in a possible case of homo- cystinuria. Recently, we experienced a 3-month-old boy with homocystinuria due to cystathionine synthased eficiency who had been discovered by the newborn screening. However, he was diagnosed as hypermethioninemia at the neonatal period and homocystinuria was not detected until three months of age by the cyanide nitroprusside test and even by amino acid autoanalysis. Therefore, it should be emphasized that urinary homocystine is repeatedly examined in a possible case of homocystinuria until the final diagnosis is established.