Dictionary

hemizygous Having only a single copy of a gene instead of the customary two copies. All the genes on the single X chromosome in the male are hemizygous.

hemochromatosis An inherited disorder characterized by abnormally high absorption of iron by the intestinal tract, resulting in excessive storage of iron, particularly in the liver, skin, pancreas, heart, joints, and testes. Common early symptoms include abdominal pain, weakness, lethargy, and weight loss. The onset of symptoms is usually between 30 to 50 years of age…

heat prostration See hyperthermia.

heat rash A red or pink rash usually found on body areas covered by clothing. It can develop when sweat ducts become blocked and swell. Symptoms may include discomfort and itching. Heat rash is most common in babies, but may affect adults in hot, humid climates. Most cases of heat rash heal by themselves, and…

heatstroke See hyperthermia.

Heberden’s disease 1 Angina. 2 Osteoarthritis of the small joints with bony enlargement (Heberden’s nodes) of the joint at the end of the finger. See also angina pectoris.

Heberden’s node A small fixed bony enlargement of the joint at the end of the finger. A Heberden’s node is a calcified spur of the bone of that joint (distal interphalangeal joint) and is associated with osteoarthritis.

Hecht syndrome An inherited disorder that is transmitted as an autosomal dominant trait, in which short, tight muscles make it impossible to open the mouth fully or keep the fingers straight when the hand is flexed back. The small mouth creates feeding problems. The hands may be so tightly fisted that infants with Hecht syndrome…

Hecht’s pneumonia See pneumonia, giant cell.

heel bone See bone, heel.

heel spur See calcaneal spur.

Heimlich maneuver An emergency treatment for obstruction of the airway in adults. The Heimlich maneuver may be needed when someone chokes on a piece of food that has “gone down the wrong way.” To perform the Heimlich maneuver, a rescuer stands behind the victim, wraps his or her arms around the victim’s waist, makes a…