SNP Shot: Genomic Insights

Molybdenum cofactor deficiency is a rare disorder causing progressive brain problems (encephalopathy). Infants appear healthy at birth, but within days experience feeding difficulties and seizures that are resistant to treatment. Brain abnormalities, including tissue breakdown (atrophy), result in significant developmental delays. Most affected individuals never achieve independent sitting or speech. Some may exhibit an excessive startle response (hyperekplexia) to sudden stimuli like loud sounds. Additional characteristics can include a small head (microcephaly) and distinct ("coarse") facial features.

Diagnostic testing shows elevated levels of sulfite, S-sulfocysteine, xanthine, and hypoxanthine in the urine and decreased uric acid levels in the blood of affected individuals.

Due to the severity of the condition, individuals with molybdenum cofactor deficiency typically do not live beyond early childhood.

Inheritance:

Molybdenum cofactor deficiency follows an autosomal recessive inheritance pattern. This means that both copies of the relevant gene in each cell must have mutations for the condition to manifest. Typically, an affected individual inherits one mutated gene copy from each parent, who usually do not exhibit symptoms themselves. However, at least one instance has been documented where an individual inherited both mutated copies of the *MOCS1* gene from a single parent through uniparental isodisomy. This occurs when an error during egg or sperm cell formation results in the child receiving two copies of the mutated gene from one parent, instead of one from each parent.