Molybdenum cofactor deficiency is a rare condition characterized by brain dysfunction (encephalopathy) that worsens over time. Babies with this condition appear normal at birth, but within a week they have difficulty feeding and develop seizures that do not improve with treatment (intractable seizures). Brain abnormalities, including deterioration (atrophy) of brain tissue, lead to severe developmental delay; affected individuals usually do not learn to sit unassisted or to speak. A small percentage of affected individuals have an exaggerated startle reaction (hyperekplexia) to unexpected stimuli such as loud noises. Other features of molybdenum cofactor deficiency can include a small head size (microcephaly) and facial features that are described as "coarse."

Molybdenum cofactor deficiency is caused by mutations in the MOCS1, MOCS2, or GPHN gene. There are three forms of the disorder, named types A, B, and C (or complementation groups A, B, and C). The forms have the same signs and symptoms but are distinguished by their genetic cause: MOCS1 gene mutations cause type A, MOCS2 gene mutations cause type B, and GPHN gene mutations cause type C. The proteins produced from each of these genes are involved in the formation (biosynthesis) of a molecule called molybdenum cofactor. Molybdenum cofactor, which contains the element molybdenum, is essential to the function of several enzymes. These enzymes help break down (metabolize) different substances in the body, some of which are toxic if not metabolized.

Molybdenum cofactor deficiency is a rare condition that is estimated to occur in 1 in 100,000 to 200,000 newborns worldwide. More than 100 cases have been reported in the medical literature, although it is thought that the condition is underdiagnosed, so the number of affected individuals may be higher.

Molybdenum cofactor deficiency has an autosomal recessive pattern of inheritance, which means both copies of the gene in each cell have mutations. An affected individual usually inherits one altered copy of the gene from each parent. Parents of an individual with an autosomal recessive condition typically do not show signs and symptoms of the condition.

Published Date: March 01, 2014
Published By: National Institutes of Health