Carney complex

Description

Carney complex is a disorder that is characterized by changes in skin coloring (pigmentation) and an increased risk of tumors. Many of the signs and symptoms of Carney complex become apparent during adolescence or early adulthood.

Almost all people with Carney complex have areas of unusual skin pigmentation. Brown or black skin spots called lentigines may appear anywhere on the body, but they tend to occur around the lips, eyes, or genitalia. In addition, some affected individuals have at least one blue-black mole called a blue nevus.

People with Carney complex have an increased risk of developing noncancerous (benign) tumors called myxomas in the heart (cardiac myxoma), skin, breast, and other parts of the body. Cardiac myxomas may be found in one or more chambers of the heart. These tumors can block the flow of blood through the heart, which can cause serious complications, including sudden death. Skin myxomas appear as small bumps on the surface of the skin or as lumps underneath the skin. In people with Carney complex, myxomas tend to recur after they are removed.

Individuals with Carney complex may also develop tumors in hormone-producing (endocrine) glands, such as the adrenal glands located on top of each kidney. Approximately 25 percent of people with Carney complex develop a specific type of adrenal tumor called primary pigmented nodular adrenocortical disease (PPNAD). PPNAD causes the adrenal glands to produce too much of the hormone cortisol. High levels of cortisol can lead to the development of Cushing syndrome, which is characterized by weight gain in the face and upper body, slow growth in children, bone loss, fragile skin, fatigue, and other health problems.

Tumors of other endocrine tissues, such as the thyroid, testes, and ovaries, are also seen in people with Carney complex. Many affected individuals have tumors on the thyroid gland called adenomas. Occasionally, people with thyroid adenomas develop thyroid cancer.

In people with Carney complex, adenomas may also form in the pituitary gland, which is located at the base of the brain. A pituitary adenoma usually causes the production of too much growth hormone. Excess growth hormone can lead to a condition called acromegaly, which is characterized by large hands and feet, arthritis, and distinctive facial features that are often described as "coarse."

Approximately 10 percent of people with Carney complex develop a rare tumor called psammomatous melanotic schwannoma (PMS). This tumor occurs in specialized cells called Schwann cells that wrap around and insulate nerve cells. These tumors are usually benign, but they can become cancerous (malignant).

Although most tumors that develop in people with Carney complex are benign, some affected individuals develop cancer over time. Complications associated with cardiac myxomas, PMS, or cancer can shorten the life expectancy for some affected individuals.

Frequency

Carney complex is a rare disorder, although the exact prevalence is unknown. At least 750 affected individuals have been reported in the medical literature. Because Carney complex is rare and the features seen in affected individuals can vary, diagnosis of the condition may be delayed.

Causes

Variants (also called mutations) in the PRKAR1A gene cause most cases of Carney complex. This gene provides instructions for making one part (subunit) of an enzyme called protein kinase A, which promotes cell growth and division (proliferation). The subunit produced from the PRKAR1A gene helps control whether protein kinase A is turned on or off.

The variants in the PRKAR1A gene that cause Carney complex reduce the number of functional regulatory subunits that are available to protein kinase A. This causes protein kinase A to be turned on more often than normal, which leads to uncontrolled cell proliferation. The signs and symptoms of Carney complex are related to the unregulated growth of cells in many parts of the body.

Some individuals with Carney complex do not appear to have a variant in the PRKAR1A gene. In some of these cases, the disorder has been associated with a specific region on the short (p) arm of chromosome 2 called 2p16. Variants in other genes appear to play a role in a few cases of Carney complex. Researchers are working to discover additional genetic factors that can cause this condition.

Inheritance

Carney complex is typically inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Approximately 30 percent of Carney complex cases result from new (de novo) variants in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development. These affected individuals typically have no history of the disorder in their family.

Autosomal dominant inheritance with a new (de novo) mutation. Credit: U.S. National Library of Medicine.

Other Names for This Condition

• Carney complex type 1
• Carney complex type 2
• Carney Syndrome
• LAMB (Lentigines, atrial myxoma, mucocutaneous myoma, blue nevi)
• NAME (Nevi, atrial myxoma, skin myxoma, ephelides)

Where this page came from

This page was imported from MedlinePlus Genetics, National Library of Medicine. Courtesy of MedlinePlus from the National Library of Medicine; its genetics summaries and the illustrations credited to the library are in the public domain. Pictures credited to others are not copied.

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