GBE1 Gene

Adult polyglucosan body disease (APBD) is a condition that affects the nervous system. People with APBD typically first experience signs and symptoms related to the condition between ages 35 and 60. Initial symptoms of the disorder include numbness and tingling in the legs (peripheral neuropathy) and progressive muscle weakness and stiffness (spasticity). As a result, affected individuals can have an unsteady gait, poor balance, and an increased risk of falling.

Damage to the nerves that control bladder function, a condition called neurogenic bladder, is another feature that often occurs early in the course of APBD. Affected individuals have increasing difficulty starting or stopping the flow of urine.

Eventually, most people with APBD lose the ability to control their bladder and bowel functions and their limbs. Damage to the autonomic nervous system, which controls body functions that are mostly involuntary, leads to problems with blood pressure, heart rate, breathing rate, digestion, temperature regulation, and sexual response, and results in daily bouts of exhaustion. About half of people with APBD experience a decline in intellectual function (dementia).

Glycogen storage disease type IV (GSD IV) is an inherited disorder caused by the buildup of a complex sugar called glycogen in the body's cells. The accumulated glycogen is structurally abnormal and impairs the function of certain organs and tissues, especially the liver and muscles. There are five types of GSD IV, which are distinguished by their severity, signs, and symptoms.

The fatal perinatal neuromuscular type is the most severe form of GSD IV, with signs developing before birth. Excess fluid may build up around the fetus (polyhydramnios) and in the fetus' body. Affected fetuses have a condition called fetal akinesia deformation sequence, which causes a decrease in fetal movement and can lead to joint stiffness (arthrogryposis) after birth. Infants with the fatal perinatal neuromuscular type of GSD IV have very low muscle tone (severe hypotonia) and muscle wasting (atrophy). These infants usually do not survive past the newborn period due to weakened heart and breathing muscles.

The congenital muscular type of GSD IV is usually not evident before birth but develops in early infancy. Affected infants have severe hypotonia, which affects the muscles needed for breathing. These babies often have dilated cardiomyopathy, which enlarges and weakens the heart (cardiac) muscle, preventing the heart from pumping blood efficiently. Infants with the congenital muscular type of GSD IV typically survive only a few months.

The progressive hepatic type is the most common form of GSD IV. Within the first months of life, affected infants have difficulty gaining weight and growing at the expected rate (failure to thrive) and develop an enlarged liver (hepatomegaly). Children with this type develop a form of liver disease called cirrhosis that often is irreversible. High blood pressure in the vein that supplies blood to the liver (portal hypertension) and an abnormal buildup of fluid in the abdominal cavity (ascites) can also occur. By age 1 or 2, affected children develop hypotonia. Children with the progressive hepatic type of GSD IV often die of liver failure in early childhood.

The non-progressive hepatic type of GSD IV has many of the same features as the progressive hepatic type, but the liver disease is not as severe. In the non-progressive hepatic type, hepatomegaly and liver disease are usually evident in early childhood, but affected individuals typically do not develop cirrhosis. People with this type of the disorder can also have hypotonia and muscle weakness (myopathy). Most individuals with this type survive into adulthood, although life expectancy varies depending on the severity of the signs and symptoms.

The childhood neuromuscular type of GSD IV develops in late childhood and is characterized by myopathy and dilated cardiomyopathy. The severity of this type of GSD IV varies greatly; some people have only mild muscle weakness while others have severe cardiomyopathy and die in early adulthood.