rare hereditary disease in which the the metabolic breakdown of glycogen to the simple sugar glucose is incomplete, allowing intermediate compounds to accumulate in the cells of the liver. Affected persons lack the enzyme amylo-1,6-glucosidase, one of several enzymes involved in glycogen breakdown. Children with the disease have enlarged livers (which usually become normal in size by puberty), are generally stunted in growth, have doll-like facial features, and experience muscular weakness. The disease is fairly mild but can cause frequent hypoglycemia (low blood sugar), producing severe convulsions that may lead to mental retardation. Forbes' disease is inherited as an autosomal recessive trait.