Autosomal recessive · Very rare; only a small number of families have been reported.
Caused by loss-of-function changes in both copies of HTRA2, which encodes a protease that helps maintain mitochondrial proteins and structure. Each parent usually carries one changed copy.
Signs and symptoms
Symptoms begin early in life, with seizures, altered muscle tone (hypertonia alternating with hypotonia), breathing and heart-and-lung problems, and raised 3-methylglutaconic acid in the urine. Other features have included a low neutrophil count and lactic acidosis. Early death has been reported.
What a diagnosis changes
Care is supportive, focusing on breathing, feeding and seizure control with specialist metabolic input. Genetic counselling and carrier testing of relatives help families understand the recurrence risk, and testing in a future pregnancy is possible once both familial variants are known.
Genes analysed
Also known as
3-methylglutaconic aciduria, type VIII; 3-methylglutaconic aciduria, type VIII; MGCA8; MGA8; MGCA8
