ANO5 Gene

Gnathodiaphyseal dysplasia is a disorder that affects the bones. People with this condition have reduced bone mineral density (osteopenia), which causes the bones to be unusually fragile. As a result, affected individuals typically experience multiple bone fractures in childhood, often from mild trauma or with no apparent cause.

While most bone tissue is less dense than normal in gnathodiaphyseal dysplasia, the outer layer (cortex) of the shafts of the long bones in the arms and legs is abnormally hard and thick (diaphyseal sclerosis). Bowing of the long bones also occurs in this disorder.

Jaw problems are common in gnathodiaphyseal dysplasia; the prefix "gnatho-" in the condition name refers to the jaw. Affected individuals may develop bone infections (osteomyelitis) in the jaw, which can lead to pain, swelling, discharge of pus from the gums, loose teeth, and slow healing after teeth are lost or extracted. Areas of the jawbone may lose the protective coverage of the gums, which can result in deterioration of the exposed bone (osteonecrosis of the jaw). Also, normal bone in areas of the jaw may be replaced by fibrous tissue and a hard material called cementum, which normally surrounds the roots of teeth and anchors them in the jaw. These areas of abnormal bone, called cementoosseous lesions, may be present at birth or develop later in life.

When gnathodiaphyseal dysplasia was first described, it was thought to be a variation of another bone disorder called osteogenesis imperfecta, which is also characterized by frequent bone fractures. However, gnathodiaphyseal dysplasia is now generally considered to be a separate condition. Unlike in osteogenesis imperfecta, the fractures in gnathodiaphyseal dysplasia heal normally without causing deformity or loss of height.

Miyoshi myopathy is a muscle disorder that begins with weakness in the muscles that are located away from the center of the body (distal muscles), such as those in the legs. During early to mid-adulthood, affected individuals typically begin to experience muscle weakness and wasting (atrophy) in one or both calves. If only one leg is affected, the calves appear different in size (asymmetrical). Calf weakness can make it difficult to stand on tiptoe.

As Miyoshi myopathy slowly worsens, the muscle weakness and atrophy spread up the leg to the muscles in the thigh and buttock and can also involve the upper arm and shoulder muscles. Eventually, affected individuals may have difficulty climbing stairs or walking for an extended period of time. Some people with Miyoshi myopathy may eventually need wheelchair assistance.

Rarely, abnormal heart rhythms (arrhythmias) have developed in people with Miyoshi myopathy. Individuals with Miyoshi myopathy have highly elevated levels of an enzyme called creatine kinase (CK) in their blood, which often indicates muscle disease.

Limb-girdle muscular dystrophy is a term for a group of diseases that cause weakness and wasting of the muscles in the arms and legs. The muscles most affected are those closest to the body (proximal muscles), specifically the muscles of the shoulders, upper arms, pelvic area, and thighs.

The severity, age of onset, and features of limb-girdle muscle dystrophy vary among the many subtypes of this condition and may be inconsistent even within the same family. Signs and symptoms may first appear at any age and generally worsen with time, although in some cases they remain mild.

In the early stages of limb-girdle muscular dystrophy, affected individuals may have an unusual walking gait, such as waddling or walking on the balls of their feet, and may also have difficulty running. They may need to use their arms to press themselves up from a squatting position because of their weak thigh muscles. As the condition progresses, people with limb-girdle muscular dystrophy may eventually require wheelchair assistance.

Muscle wasting may cause changes in posture or in the appearance of the shoulder, back, and arm. In particular, weak shoulder muscles tend to make the shoulder blades (scapulae) "stick out" from the back, a sign known as scapular winging. Affected individuals may also have an abnormally curved lower back (lordosis) or a spine that curves to the side (scoliosis). Some develop joint stiffness (contractures) that can restrict movement in their hips, knees, ankles, or elbows. Overgrowth (hypertrophy) of the calf muscles occurs in some people with limb-girdle muscular dystrophy.

Weakening of the heart muscle (cardiomyopathy) occurs in some forms of limb-girdle muscular dystrophy. Some affected individuals experience mild to severe breathing problems related to the weakness of muscles needed for breathing. In some cases, the breathing problems are severe enough that affected individuals need to use a machine to help them breathe (mechanical ventilation).

Intelligence is generally unaffected in limb-girdle muscular dystrophy; however, developmental delay and intellectual disability have been reported in rare forms of the disorder.