Thrombocytopenia in malaria : who cares ? Marcus

Malaria affects almost all blood components and is a true haematological infectious disease. Anaemia and thrombocytopenia are the most frequent malaria-associated haematological complications (Wickramasinghe & Abdalla 2000) and have received more attention in the scientific literature due to their associated mortality. On the other hand, thrombocytopenia is less studied, causes negligible mortality and is an isolated phenomenon; there is no report of a single patient in the literature who has died only because of malaria-associated thrombocytopenia. In the current field of Travel Medicine, the rapid increase in the number of people travelling to tropical areas has added a great challenge for malaria diagnosis because the thick blood smear (the standard diagnosis in endemic areas) has high specificity but only when performed by experienced microscopists. The presence of thrombocytopenia in acute febrile travellers returning from tropical areas has become a highly sensitive clinical marker for malaria diagnosis (D’Acremont et al. 2002). Another study has reported 60% sensitivity and 88% specificity of thrombocytopenia for malaria diagnosis in acute febrile patients (Lathia & Joshi 2004). The sensitivity of thrombocytopenia together with the acute febrile syndrome was 100% for malaria diagnosis, with a specificity of 70%, a positive predictive value of 86% and a negative predictive value of 100% (Patel et al. 2004). Thrombocytopenia is a well-documented and frequent complication in Plasmodium vivax malaria. In one study, platelet count normalised after treatment and only one patient, concomitant with the lowest platelet count, exhibited “purpuric lesions” on the lower extremities (Hill et al. 1964). Since the beginning of the 1970s, there have been reports proposing that malaria-associated thrombocytopenia is quite similar in P. vivax and Plasmodium falciparum infections (Beale et al. 1972). However, more recent data in India has shown how thrombocytopenia exhibited a heightened frequency and severity among patients with P. vivax infection (Kochar et al. 2010). In 1903, the young physician Carlos Chagas (who become more famous afterwards for the discovery of American trypanosomiasis, which is named after him), published his MD thesis on the Hematological Studies on Paludism (Chagas 1903). Within it, he described anaemia and leukocyte abnormalities, but also normal megakaryocytes in the bone marrow were referred to in patients with acute and chronic malaria from Rio de Janeiro. He also drew our attention to evidence of bleeding in the 46 patients he followed. In the city of Manaus, state of Amazonas, located in the Western Brazilian Amazon, Djalma Batista authored Paludism in the Amazon, a book in which he described observations about patients with malaria seen at his private clinics (Batista 1946). Similar to Carlos Chagas, there is no mention of platelet count in his study because it was not routinely performed. However, there is a vivid description of haemostasis disorders in some patients. Particularly noteworthy is the presence of huge spleen enlargement and prolonged bleeding time accompanied by recurrent gingival bleeding. Financial support: CAPES (scholarship for HCCC), CNPq (MVGL is a level 2 research productivity fellow), ASH + Corresponding author: [email protected] Received 1 April 2011 Accepted 26 May 2011 Thrombocytopenia in malaria: who cares?