Familial thrombocytosis in which the cause of the disease is a mutation in the MPL gene. The disease is thrombocythemia 2 (MONDO_0011173, a Monarch Disease Ontology entry). Also known as: MPL familial thrombocytosis, familial thrombocytosis caused by mutation in MPL, thrombocythemia 2, autosomal dominant, somatic mutation, thrombocythemia type 2.