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AimTo characterise the clinical and histological features of MPL-mutated essential thrombocythaemia (ET).Patients and methodsBone marrow biopsies of 175 patients with ET were centrally reviewed according to the 2016 WHO classification, including 42 cases with MPL mutation, 98 JAK2V617F-mutated and 35 CALR-mutated. Clinical and histological features were compared among the three genotypes included in the current 2016 WHO classification and among the different types of MPL mutations.ResultsPatients with MPL-mutated ET were significantly older than those with the other genotypes. Haematological values at diagnosis were similar among MPL-mutated and CALR-mutated ET, with both genotypes showing higher platelet counts and lower haemoglobin values than ET with JAK2V617F genotype. In the bone marrow, the median number of megakaryocytes was higher in MPL and CALR than in JAK2V617F genotype (16, 19 and 14 megakaryocytes per ×20 power field, respectively, p=0.004). Histological features of prefibrotic myelofibrosis were rarely observed in MPL genotype, whereas sinusoidal hyperplasia, dense clusters of megakaryocytes and reticulin fibrosis were more frequent in CALR-mutated ET, with 11% of such cases fulfilling WHO 2016 histological criteria of prefibrotic myelofibrosis. With a median follow-up of 3.5 years, no significant differences were seen among genotypes regarding survival, vascular complications or myelofibrotic transformation. There were no significant differences in the clinical data or in the histological characteristics depending on the type of MPL mutation.ConclusionMPL and CALR ET genotypes share clinical and histological characteristics. In contrast to CALR genotype, features of prefibrotic myelofibrosis are uncommon in MPL-mutated ET.

We report here a case of drug-related thrombo-cytopenia associated with infliximab and later with adalimumab in a patient with Crohn’s disease. A 42-year-old woman was diagnosed with colonic Crohn’s disease with perianal fistula lesions (Perianal Disease Activity Index (PDAI) = 11). She was treated with metronidazole and azathioprine. After 2 months the patient remained symptomatic and three infusions with infliximab (monoclonal antibody against tumour necrosis factor α (TNFα)) at a dose of 5 mg/kg were administered at 0, 2 and 6 weeks. The symptoms decreased and improvement was noted (PDAI = 2). Maintenance therapy with infliximab every 8 weeks was started. After three additional infusions, a routine blood count showed thrombocytopenia of 44×109/l (fig 1) with normal haemoglobin, white blood cell count and coagulation tests. Pseudo-thrombocytopenia …