Congenital amegakaryocytic thrombocytopenia - Not a single disease

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare inherited bone marrow failure syndrome (IBMFS) that is characterized by severe thrombocytopenia at birth due to ineffective megakaryopoiesis and development towards aplastic anemia during the first years of life. CAMT is not a single monogenetic disorder; rather, many descriptions of CAMT include different entities with different etiologies. CAMT in a narrow sense, which is primarily restricted to the hematopoietic system, is caused mainly by mutations in the gene for the thrombopoietin receptor (MPL), sometimes in the gene for its ligand (THPO). CAMT in association with radio-ulnar synostosis, which is not always clinically apparent, is mostly caused by mutations in MECOM, rarely in HOXA11. Patients affected by other IBMFS - especially Fanconi anemia or dyskeratosis congenita - may be misdiagnosed as having CAMT when they lack typical disease features of these syndromes or have only mild symptoms. This article reviews scientific and clinical aspects of the various disorders associated with the term "CAMT" with a main focus on the disease caused by mutations in the MPL gene.

Advances in the understanding of congenital amegakaryocytic thrombocytopenia

Congenital amegakaryocytic thrombocytopenia (MIM #604498) is an extremely rare inherited bone marrow failure syndrome, usually presenting as a severe thrombocytopenia at birth due to ineffective megakaryocytopoiesis and no characteristic physical anomalies. Usually the isolated thrombocytopenia progresses to pancytopenia during the first years of life. The only curative therapy to date is haematopoietic stem cell transplantation. Most of the cases of congenital amegakaryocytic thrombocytopenia are caused by defective expression or function of the thrombopoietin receptor due to homozygous or compound heterozygous mutations in the gene MPL. The essential roles of thrombopoietin as a lineage specific regulator of platelet production and as a regulator of haematopoietic stem cell function are reflected in the haematological defects seen in affected individuals.