Congenital amegakaryocytic thrombocytopenia (CAMT) is a disorder characterized by reduced platelet levels and the absence or reduction of megakaryocytes, the platelet-producing bone marrow cells.
CAMT is linked to an increased risk of leukemia and presents in two types. Type I CAMT, with complete gene/protein inactivity, results in severe symptoms. Affected individuals typically experience bleeding, which can manifest on the skin, in the gastrointestinal and pulmonary systems, or within the brain, often starting in infancy. This type progresses to bone marrow failure around age 4. Type II CAMT, with partial gene/protein activity, leads to milder symptoms. It may also appear in infancy but not necessarily immediately after birth. If bone marrow failure occurs in type II, it typically happens later than in type I, usually by age 10. Bone marrow transplantation (BMT)/stem cell transplant (SCT) has been shown to successfully cure congenital amegakaryocytic thrombocytopenia, but there is an approximately 20% mortality rate associated with the procedure. When BMT/SCT is not performed, treatments (like platelet transfusion) may be helpful in the short-term, though they cannot prevent all complications.
CAMT is caused by pathogenic (disease-causing) variants in the MPL gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 57 chance to be a carrier.