Engelmann disease

Definition

Engelmann disease is a rare genetic condition that causes the long bones in the legs to become abnormally wide and may change the structure of other bones in the body. Its effects include bone pain (especially in the legs), skeletal disorders, and weak, underdeveloped leg muscles.

Description

Despite their strength and durability, human bones are living organisms. Throughout the life span, bones are constantly being broken down and rebuilt again without losing their proper size and shape. Diseases that interfere with this delicately orchestrated process (called bone remodeling) can produce pain and restrict our freedom of movement. In Engelmann disease, which was first described in 1920, the shafts of the long bones in the legs become thicker than normal. The femur (thigh bone) and tibia (shin bone) are primarily affected. These changes often cause severe bone pain and weak muscles in the legs. The weak, aching muscles associated with Engelmann disease may result in an unusual walk that resembles a "waddle." People with Engelmann may be bow-legged and have thin, elongated legs that look as if they are "wasting away."

Aside from bones in the leg, Engelmann disease can cause abnormal changes in other bones. People with Engelmann may develop scoliosis (in which the spine curves to the left or right side) or lumbar lordosis (a forward curvature of the spine). Engelmann disease can also cause bones to become abnormally hardened (a process referred to as sclerosis). This hardening can affect the bones at the base of the skull as well as those in the hands and feet. In rare cases, sclerosis may affect the jaw. Bone pain and aching, weak muscles may occur in parts of the body affected by the disease.

Engelmann can also affect internal organs and sight. The liver and spleen may become enlarged. Loss of vision may occur if bones near the eye sockets are affected. Some people with Engelmann report headaches, fatigue, and lack of appetite.

The underlying cause of Engelmann disease is unknown. It is often referred to in the medical literature as Camurati-Engelmann disease or progressive diaphyseal dysplasia (PDD). Less common names for the condition include osteopathia hyperostotica scleroticans and multiplex infantalis. Engelmann disease was sometimes referred to as ribbing disease in the past but this name is no longer used.

Genetic profile

Engelmann is considered an inherited disease, though occasionally mutations may produce sporadic cases. It is passed from parent to child as an autosomal dominant trait. This means that a person may develop the condition after receiving just one copy of the abnormal gene (associated with Engelmann disease) from either the mother or father.

While the gene (or genes) responsible for Engelmann disease is still unknown, medical researchers have narrowed their search to a specific region of human DNA , which may eventually lead to identification. This chromosomal region is known as 19q13. A gene known as TGFB1 (transforming growth factor-beta 1), which plays a role in regulating bone growth, is located in this region and is therefore considered a possible candidate.

Demographics

Engelmann, which affects men and women equally, is a very rare disease that develops during childhood or young adulthood. It usually develops between ages four and ten, but may affect children as young as three months old. Other people may develop Engelmann disease any-time before age 30.

Signs and symptoms

The main symptoms of Engelmann disease are severe pain in the legs, weak and underdeveloped leg muscles, and a "waddling" walk. Other symptoms include bowed legs, unusually long limbs, spine problems such as scoliosis or lumbar lordosis, and flat feet. People with the disease may complain of headaches, lack of energy or appetite, vision problems, and an aching feeling in their hands and feet and, less often, in the jaw. Infants with Engelmann disease may experience feeding problems or a failure to thrive, and have a "malnourished" appearance.

In simple terms, Engelmann disease causes telltale changes in the structure of the femur and tibia, around the mid-shaft areas. Certain bone regions (specifically, the endosteal and periosteal surfaces) become abnormally thickened and hardened, which in turn narrows the medullary canal. Engelmann disease also causes the long bones to become "fusiform," a technical term indicating a tapered, spindle-like shape. In addition to these changes, Engelmann may cause abnormal hardening of other bones: in the hands and feet, at the base of the skull, and in the jaw. Engelmann may also involve liver and spleen enlargement, compression of the optic nerves, and increased intracranial pressure.

Diagnosis

Classic symptoms such as severe leg pain, underdeveloped leg muscles, and a "waddling" gait are often the first indication of the disease. An infant may initially experience feeding problems or failure to thrive (though these are more often the result of other, less serious problems). Imaging procedures such as a CT scan are used to detect the bone abnormalities associated with the condition, which mainly involve the thickening and sclerosis of the long bones of the legs. In some cases, x-ray studies of the skull are necessary. Blood tests and a biopsy of muscle tissue may be recommended.

In diagnosing Engelmann disease, a doctor must distinguish it from other conditions that produce similar symptoms, such as Paget disease and certain types of muscular dystrophy .

Treatment and management

The treatment of Engelmann disease focuses on alleviating symptoms. While the changes in bone associated with the condition cannot be reversed, the use of steroid drugs such as cortisone or prednisone can ease bone pain and strengthen muscle. Surgery to repair muscles or bones is rarely necessary, while procedures to repair nerves in the eye are generally considered ineffective.

Prognosis

While Engelmann disease does not affect life expectancy, the prognosis for the condition varies. Some people affected by the disease are virtually free of symptoms; others are severely disabled. In some cases, the muscle weakness associated with Engelmann diminishes or goes away completely with the passage of time. In other people, the effects of the disease seem to remain the same or slowly worsen during adulthood.

Resources

BOOKS

Jones, Kenneth L., ed. Smith's Recognizable Patterns of Human Malformation. 5th ed. Philadelphia: W.B. Saunders, 1997.

PERIODICALS

Janssens, K., et al. "Localisation of the gene causing diaphyseal dysplasia Camurati-Engelmann to chromosome 19q13." Journal of Medical Genetics 37, no. 4 (2000): 245–9.

Kinoshita, A., T. Saito, H. Tomita, et al. "Domain-specific mutations in TGFB1 result in Camurati-Engelmann disease." Nature Genetics 26, no. 1 (2000): 19–20.

ORGANIZATIONS

National Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse. One AMS Circle, Bethesda, MD 20892-3675. (301) 495-4484.

National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. <http://www.rarediseases.org>.

WEBSITES

Genetic Alliance. <http://www.geneticalliance.org>.

National Organization for Rare Disorders (NORD). <http://www.rarediseases.org>.

Greg Annussek