Affected family members show elevated platelet counts, decreased platelet volume, and highly elevated THPO serum levels. (A) Family tree of the described patients. (B) Table showing age, complete blood counts white blood cells (WBC) (numbers per nanoliter), red blood cells (RBC) (numbers per picoliter), hemoglobin (Hb) (g/dL), platelet count (Plt), and mean platelet volume (MPV) (in fl) of the consanguineous family with HT. The numbers represent a single measurement, but are representative of serial blood test over several months. (C) Serum thrombopoietin levels of a healthy control and members of the described family were measured in pg/mL in serum using a THPO enzyme-linked immunosorbent assay, as described in “Materials and methods.”