A number of clinical and laboratory parameters were evaluated for possible association with the presence of ⩾grade 1 BM reticulin fibrosis and none, including age (P=0.1), sex (P=0.7), hemoglobin level (P=0.9), leukocyte count (P=0.6), leukocytosis ⩾11 × 109/l (P=0.6), leukocytosis ⩾15 × 109/l (P=0.5), platelet count (P=0.4), presence of palpable splenomegaly (P=0.3), pruritus (P=0.5), erythromelalgia (P=0.7) or mutations (JAK2, P=0.2; TET2, P=0.4; ASXL1, P=0.3) displayed a significant association (Table 1). This evidence concerns the gene JAK2 and Splenomegaly.