hereditary thrombocytosis with transverse limb defect (Monarch Disease Ontology identifier MONDO_0018000) can be described as follows. Thrombocythemia with distal limb defects is a rare, genetic syndrome with limb reduction defects characterized by thrombocytosis, unilateral transverse limb defects (ranging from absence of phalanges to absence of hand or forearm) and splenomegaly. Also known as: familial thrombocytosis with transverse limb defect.