Research Article
Jan Jacques Michiels, Achil
Abstract
We analysed the clinical and hematological features in 41 patients of seven families, including 21 ET patients with a proven MPLS505N mutation and 20 relatives with thrombocythemia reported in the medical records. Out of the 41 MPLS505N mutated individuals 15 major thrombotic episodes in 14 members (34%) were reported as Budd-Chiari syndrome age 17 in 1, deep vein thrombosis leg age 41 in 1,ecclampsia and fetal in 1, stroke at ages 43, 72, 76 and 80 in 4 and myocardial infarction at ages between 31-81 years, median 52 years. Fourteen out of 21 well documented MPLS505N mutated ET patients had no splenomegaly and were free of major thrombosis during follow-up at ages between 2 and 76 years (mean 31 years). Eight MPLS505N mutated patients had myelofibrosis (MF) from grade MF1 in 5 to grade MF2 in 3 at ages between 28-80 years (mean 48 years), which was associated with mild to moderate splenomegaly (spleen length diameter 14.5 to 18 cm). Six anemic cases at hemoglobin levels between 10 and 11.9 g/dL had platelet counts between 317 and 963 × 109 /L. Among 15 family members 9 died from thrombosis in 3, hypocellular myelofibrosis (two of them at age 76 and 80 years) in 3, and cancer or undefined in 3 cases. The maximum life expectancy of MPLS505N family members with thrombocythemia was 50% at 80 years, and 90% at 80 years of non-affected family members without thrombocythemia. The clinical presentation in 30 ET patients with acquired MPL505N mutation (9 males and 21 females, age 22-84 (mean 56 years of whom 18 had the W515L and 12 the W515K) was featured by a high incidence of major arterial event in 23%, venous thrombosis in 10%, aspirin responsive microvessel disturbances in 60%, and major hemorrhage in 7%. The only abnormal laboratory finding in MPL mutated ET was increased platelet counts, 956+331 × 109 /L in all and slight splenomegaly in 5 (17%). Bone marrow histology from patients ET carrying the MPL505N mutation consistently displayed a normocellular bone marrow with clustered small and large to giant megakaryocytes with hyperlobulated stag-horn nuclei and no features of polycythemia vera (PV) in blood and bone marrow.