Glutaric acidemia type II

Other Names: Glutaric acidemia type 2; Glutaric acidemia 2; Glutaric aciduria 2; GA 2; Ethylmalonic-adipicaciduria; Multiple Acyl-CoA dehydrogenase deficiency; EMA; MADD

Glutaric acidemia type II is an inherited disorder that interferes with the body's ability to break down proteins and fats to produce energy. Incompletely processed proteins and fats can build up in the body and cause the blood and tissues to become too acidic (metabolic acidosis).

Epidemiology

Glutaric acidemia type II is a very rare disorder; its precise incidence is unknown. It has been reported in several different ethnic groups.

Cause

Mutations in any of three genes, ETFA, ETFB, and ETFDH, can result in glutaric acidemia type II. The ETFA and ETFB genes provide instructions for producing two protein segments, or subunits, that come together to make an enzyme called electron transfer flavoprotein.

The ETFDH gene provides instructions for making another enzyme called electron transfer flavoprotein dehydrogenase.

Glutaric acidemia type II is caused by a deficiency in either of these two enzymes. Electron transfer flavoprotein and electron transfer flavoprotein dehydrogenase are normally active in the mitochondria, which are the energy-producing centers of cells. These enzymes help break down proteins and fats to provide energy for the body. When one of the enzymes is defective or missing, partially broken down nutrients accumulate in the cells and damage them, causing the signs and symptoms of glutaric acidemia type II.

People with mutations that result in a complete loss of either enzyme produced from the ETFA, ETFB or ETFDH genes are likely to experience the most severe symptoms of glutaric acidemia type II. Mutations that allow the enzyme to retain some activity may result in milder forms of the disorder.

Inheritance

Autosomal recessive inheritance, a 25% chance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

Signs and symptoms of glutaric acidemia type II (GA2) can vary widely depending on the age of onset and severity of the condition in each affected individual. In most cases, the condition appears in infancy or early childhood as a sudden episode called a metabolic crisis which causes weakness; behavior changes such as poor feeding and decreased activity; and vomiting. These crises can be life-threatening and may be triggered by common childhood illnesses or other stresses on the body.

The most severe cases may appear in the neonatal period (within the first 4 weeks of life) and may also be characterized by the presence of physical abnormalities at birth. These abnormalities may include brain malformations; an enlarged liver (hepatomegaly); a weakened and enlarged heart (dilated cardiomyopathy); fluid-filled cysts and other malformations of the kidneys; unusual facial features; and genital abnormalities. Some affected individuals have a characteristic odor resembling sweaty feet.

Other cases are less severe and may appear later in childhood, in adolescence, or in adulthood. In the most mild cases, muscle weakness may be the first sign of the disorder.

Diagnosis

The diagnosis of MADD is established in a proband with elevation of several acylcarnitine species in blood in combination with increased excretion of multiple organic acids in urine and/or by identification of biallelic pathogenic variants in ETFA, ETFB, or ETFDH.

Treatment

The goal of treatment is to prevent long-term problems. However, children who have repeated metabolic crises may develop life-long learning problems. Individuals with glutaric acidemia type II should consult with a metabolic doctor and a dietician who can help to develop an appropriate dietary plan. Some treatments may be recommended for some children but not for others. When necessary, treatment should be continued throughout the lifetime.

The following treatments are often recommended:

• Avoidance of fasting. Infants and young children with glutaric acidemia type II should eat frequent meals in order to prevent hypoglycemia and metabolic crises.
• A low-fat, low-protein, high-carbohydrate diet may be advised.
• Riboflavin, L-carnitine and glycine supplements may be needed. These supplements help the body create energy.
• Alert the child's doctor if they should become ill, as illness can trigger a metabolic crisis.

NIH genetic and rare disease info

• NIH info on Glutaric acidemia type II

Glutaric acidemia type II is a rare disease.

Glutaric acidemia type II Resources
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