Summary. Background: Distinguishing inherited thrombocytopenias from immune thrombocytopenia (ITP) can be difficult, and patients are therefore at risk of misdiagnosis and inappropriate treatments. Although it is known that the most common inherited forms of thrombocytopenia are characterized by increased platelet size, the diagnostic power of this feature has never been investigated. Objectives: The aim of this study was to test the hypothesis that platelet size can be used to differentiate ITP from inherited macrothrombocytopenias. Patients/ methods: We measured mean platelet volume (MPV) and mean platelet diameter (MPD), within 2 h of blood sampling, in 35 patients with inherited macrothrombocytopenias [15 MYH9-related disease (MYH9-RD), three biallelic and 17 monoallelic Bernard-Soulier syndrome (BSS)], and 56 with ITP. Using receiving operating characteristic analysis, we searched for the best cut-off values to differentiate between these conditions. Results: As expected, platelets were larger in inherited macrothrombocytopenias than in ITP. An MPD larger than 3.3 lm differentiated MYH9-RD and BSS from ITP with 0.89 sensitivity and 0.88 specificity, and an MPV larger than 12.4 fL had 0.83 sensitivity and 0.89 specificity. Combining MPD with MPV increased sensitivity and specificity to 0.97 and 0.89, respectively. Conclusion: Platelet size evaluation by both an appropriate cell counter and blood film examination is useful for differentiating inherited macrothrombocytopenias from ITP.

Deep venous thrombosis (DVT) has been variably reported in multiple myeloma patients during treatment with thalidomide alone or in combination with chemotherapy or dexamethasone. With the aim of investigating this complication, we performed, on a cohort of 13 relapsed refractory MM patients treated with low-dose thalidomide (100 mg/day) and dexamethasone (20 mg p.o./day for 4 days every 2 weeks), a serial evaluation of different laboratory parameters implicated in DVT. No significant abnormalities in all genetic, serologic, or plasmatic parameters studied were registered, apart from thrombomodulin which showed significant variations between baseline and 1st-month values and 1st- and 3rd-month values. In conclusion, the evidence of significant variations of thrombomodulin values in the 1st month of therapy, which is considered to involve the highest risk of thrombosis, might support a role for thrombomodulin in this complex mechanism.

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