Forbes' disease

Forbes' Disease, also known as Glycogen Storage Disease Type III (GSD III), is a rare genetic disorder that affects the body's ability to store and use glycogen, a form of sugar stored in the liver and muscles for energy. This condition is part of a group of diseases known as glycogen storage diseases, which are characterized by the accumulation or improper utilization of glycogen in the body. Forbes' Disease is caused by mutations in the AGL gene, which provides instructions for making an enzyme necessary for breaking down glycogen. The absence or deficiency of this enzyme leads to the abnormal buildup of glycogen, causing various symptoms and complications.

Symptoms and Complications

The symptoms of Forbes' Disease can vary widely among affected individuals, depending on the severity of the enzyme deficiency. Common symptoms include hypoglycemia (low blood sugar), muscle weakness, hepatomegaly (enlarged liver), and growth retardation. In some cases, affected individuals may also experience cardiomyopathy (heart muscle disease), liver cirrhosis, and difficulties in metabolism.

Diagnosis

Diagnosis of Forbes' Disease typically involves a combination of physical examination, patient history, laboratory tests measuring enzyme activity in the liver or muscle tissues, and genetic testing to identify mutations in the AGL gene.

Treatment

There is no cure for Forbes' Disease, but treatment focuses on managing symptoms and preventing complications. Dietary management, including frequent high-carbohydrate meals or cornstarch therapy, can help prevent hypoglycemia. Physical therapy may be recommended to address muscle weakness. In severe cases, liver transplantation may be considered if liver cirrhosis or liver failure occurs.

Epidemiology

Forbes' Disease is a rare condition, with an estimated incidence of 1 in 100,000 live births. It affects individuals of all ethnic backgrounds, although certain mutations in the AGL gene may be more common in specific populations.

Genetics

The AGL gene mutations responsible for Forbes' Disease are inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to be affected by the disease. Carriers of one mutated gene typically do not show symptoms of the disease but have a 50% chance of passing the mutated gene to their offspring.