KIT Gene

Piebaldism is a condition characterized by the absence of cells called melanocytes in certain areas of the skin and hair. Melanocytes produce the pigment melanin, which contributes to hair, eye, and skin color. The absence of melanocytes leads to patches of skin and hair that are lighter than normal. Approximately 90 percent of affected individuals have a white section of hair near their front hairline (a white forelock). The eyelashes, the eyebrows, and the skin under the forelock may also be unpigmented.

People with piebaldism usually have other unpigmented patches of skin, typically appearing symmetrically on both sides of the body. There may be spots or patches of pigmented skin within or around the borders of the unpigmented areas.

In most cases, the unpigmented areas are present at birth and do not increase in size or number. The unpigmented patches are at increased risk of sunburn and skin cancer related to excessive sun exposure. Some people with piebaldism are self-conscious about the appearance of the unpigmented patches, which may be more noticeable in darker-skinned people. Aside from these potential issues, this condition has no effect on the health of the affected individual.

A gastrointestinal stromal tumor (GIST) is a type of tumor that occurs in the gastrointestinal tract, most commonly in the stomach or small intestine. This type of tumor is thought to grow from specialized cells found in the gastrointestinal tract called interstitial cells of Cajal (ICCs) or precursors to these cells. Affected individuals can develop one or more tumors. GISTs are usually found in adults between ages 40 and 70; rarely, children and young adults develop this type of tumor.

Small tumors may cause no signs or symptoms. However, some people with GISTs may experience pain or swelling in the belly area (abdomen), nausea, vomiting, loss of appetite, or weight loss. Sometimes, tumors cause bleeding into the gastrointestinal tract, which may lead to low red blood cell counts (anemia) and, consequently, weakness and tiredness. Bleeding into the intestines may cause black and tarry stools, and bleeding into the throat or stomach may cause vomiting of blood.

Affected individuals with no family history of GIST typically have only one tumor (called a sporadic GIST). People with a family history of GISTs (called familial GISTs) often have multiple tumors and additional signs or symptoms, including noncancerous overgrowth (hyperplasia) of other cells in the gastrointestinal tract and patches of dark skin on various areas of the body. Some affected individuals have a skin condition called urticaria pigmentosa (also known as maculopapular cutaneous mastocytosis), which is characterized by raised patches of brownish skin that sting or itch when touched.

A rare form of GIST, called succinate dehydrogenase (SDH)-deficient GIST, tends to occur in childhood or young adulthood and affects females more commonly than males. In this form, tumors are almost always in the stomach. Individuals with an SDH-deficient GIST have a high risk of developing other types of tumors, particularly noncancerous tumors in the nervous system called paragangliomas and noncancerous lung tumors called pulmonary chondromas. When GISTs occur in combination with paragangliomas, the condition is known as Carney-Stratakis syndrome; the combination of GISTs, paragangliomas, and pulmonary chondromas is known as Carney triad; and the combination of GISTs and pulmonary chondroma is known as incomplete Carney triad.

Core binding factor acute myeloid leukemia (CBF-AML) is one form of a cancer of the blood-forming tissue (bone marrow) called acute myeloid leukemia. In normal bone marrow, early blood cells called hematopoietic stem cells develop into several types of blood cells: white blood cells (leukocytes) that protect the body from infection, red blood cells (erythrocytes) that carry oxygen, and platelets (thrombocytes) that are involved in blood clotting. In acute myeloid leukemia, the bone marrow makes large numbers of abnormal, immature white blood cells called myeloid blasts. Instead of developing into normal white blood cells, the myeloid blasts develop into cancerous leukemia cells. The large number of abnormal cells in the bone marrow interferes with the production of functional white blood cells, red blood cells, and platelets.

People with CBF-AML have a shortage of all types of mature blood cells: a shortage of white blood cells (leukopenia) leads to increased susceptibility to infections, a low number of red blood cells (anemia) causes fatigue and weakness, and a reduction in the amount of platelets (thrombocytopenia) can result in easy bruising and abnormal bleeding. Other symptoms of CBF-AML may include fever and weight loss.

While acute myeloid leukemia is generally a disease of older adults, CBF-AML often begins in young adulthood and can occur in childhood. Compared to other forms of acute myeloid leukemia, CBF-AML has a relatively good prognosis: about 90 percent of individuals with CBF-AML recover from their disease following treatment, compared with 25 to 40 percent of those with other forms of acute myeloid leukemia. However, the disease recurs in approximately half of them after successful treatment of the initial occurrence.