Homocystinuria

Disease Overview

Homocystinuria refers to a group of inherited disorders in which the body is unable to process certain building blocks of proteins (amino acids) properly. This leads to increased amounts of homocysteine and other amnio acids in the blood and urine. The most common type of genetic homocystinuria, called CBS deficiency, is caused by the lack of an enzyme known as cystathionine beta-synthase (CBS). Most states in the United States test for homocystinuria due to CBS deficiency at birth by newborn screening.   Other types are less common, and are caused by different missing or non-working enzymes.  Homocystinuria can affect the eyes, skeleton, central nervous system and the blood clotting system. Mutations in the MTHFR, MTR, MTRR and MMADHC genes can cause homocystinuria. All these forms of homocystinuria are inherited in an autosomal recessive manner.[3151] Treatment and long-term outlook varies depending upon the cause of the disorder.