Thrombocytopenia in idiopathic inflammatory myopathies: a case series analysis

Idiopathic inflammatory myopathies (IIM) are a group of rare connective tissue diseases (CTDs) deeply affecting patients' prognosis. Extra-muscular involvement is not rare and skin, joints and lung are the most common targets. However, also dyserythropoiesis has been described, carrying relevant issues on patients' management and follow-up, as for example, lymphopenia has been associated with an increased risk of rapid progressive interstitial lung disease in anti-MDA5 positive dermatomyositis. Conversely to systemic lupus erythematosus, thrombocytopenia has only been rarely described in IIM and very few authors focused on its potential prognostic implications. We describe five cases of thrombocytopenia in IIM patients positive for myositis specific (MSA) or associated (MAA) autoantibodies. These reports extend the spectrum of haematological features associated to IIM, focusing also on potential risk factors for thrombocytopenia occurrence.