What causes Carney complex?

Carney complex is caused by a mutation in a specific gene or genes. It can be inherited (passed from parent to child), or it can occur randomly.

Most cases of Carney complex are caused by a change or mutation in the PRKAR1A gene. Researchers think that this gene, located on chromosome 17, usually suppresses or prevents tumor growth. But the genetic mutation in Carney complex makes the gene promote or cause tumor growth.

In some cases, mutations in genes on chromosome 2—PRKACA, PRKCAB, PDE11A, or PDE8B—cause Carney complex.^1,2

Carney complex may also occur when a genetic mutation occurs randomly, meaning other family members do not have the mutated gene. Healthcare providers call these sporadic or de novo mutations.^1,2

Up to about one-third of people with Carney complex symptoms have no mutations in genes linked to the condition. For this reason, a negative genetic test result does not always mean a person does not have Carney complex—especially if another family member has it. Researchers are working to identify additional genes that may cause or contribute to Carney complex.^1,2

About Inheritance of Carney Complex

Genes are pieces of DNA that carry the instructions for “building” a body and controlling its functions. Chromosomes are packages of genes and other materials. Because chromosomes exist in pairs, people usually have two copies of a single gene—one on each chromosome in the pair. Most people have 23 pairs of chromosomes—22 numbered chromosomes and 1 sex chromosome (XX for females and XY for males).

Carney complex genes pass from one generation to the next through autosomal dominance. Autosomal means the gene is on a numbered chromosome, such as chromosome 17, instead of a sex chromosome. Dominance means that a change or mutation in just one copy of the gene causes the condition. The mutated gene “dominates” the nonmutated gene.

But not everyone who has the mutated gene will develop symptoms of Carney complex. In some cases, despite the mutated gene, the person does not develop the disease or develops only mild symptoms. This situation is called “incomplete penetrance,” which means that the mutation does not always cause clinical symptoms.

Each child of a parent who has the mutated gene has a 50% chance of having the same genetic mutation. For this reason, genetic counseling is important for people with Carney complex who plan to have a family.^1,2