Hemihypertrophy (Hemihyperplasia) Health Article

Definition

Hemihypertrophy, more correctly termed hemihyperplasia, is defined as the enlargement of one side of the body or part of the body.

Description

Hemihypertrophy is characterized by unequal (asymmetric) growth of the cranium, face, trunk, limbs, and/or digits. Hemihypertrophy can be an isolated finding, or it can be associated with certain malformation syndromes. Isolated hemihypertrophy refers to hemihypertrophy for which no cause can be found. The degree of asymmetry is variable and very mild cases can go undiagnosed. There are three categories of hemihyper-trophy, depending on the body parts involved. The size difference can involve only a specific part of the body

such as a finger (called simple hemihypertrophy) or an entire half of the body (called total or complex hemihypertrophy). It usually involves only one side of the body, but can involve both sides (called crossed). There is also hemifacial hyperplasia, which involves one side of the face. Usually multiple organ systems are involved, i.e. the skin, vascular system, internal organs, or bones. In complex hemihypertrophy, the right side is more often involved than the left.

Hemihypertrophy may involve not only the part of the body that is visible, but also the underlying internal organs. Enlargement of one kidney, adrenal gland, testis, and ovary has been reported. The enlarged area usually also has thickened skin, more sebaceous (sweat) glands, more hair, may have pigmentary abnormalities, and the bones may be larger or may be deformed. In persons with facial involvement, the asymmetry can include cheek, lip, nose, ear, eye, tongue, jaw, roof of the mouth, or teeth.

The nervous system may also be affected, causing unilateral nerve enlargement or sciatic nerve inflammation. Occasionally a part of the brain is affected causing mental retardation (15% to 20% of cases). Many cases of hemihypertrophy have hamartomatous lesions (birth marks which involve blood vessels) or abnormalities of the genito-urinary system.

As with other overgrowth syndromes, there is an increased risk for childhood cancers in people with isolated hemihypertrophy (about 6%), particularly cancers of the kidney (Wilms tumor, 3% of individuals), adrenals, and liver.