Immune Thrombocytopenic Purpura Secondary to Histoplasmosis

Abstract

Immune thrombocytopenic purpura (ITP) is a relatively common acquired bleeding disorder characterized by autoimmune destruction of platelets. In adults, the annual incidence is around 1.6/100,000, common in middle aged females. In patients with ITP, physical examination is usually normal aside from bleeding manifestations, such as petechiae, ecchymoses, and purpura. The three key diagnostic criteria for ITP are isolated thrombocytopenia with otherwise normal peripheral complete blood count and smear, an absence of hepatosplenomegaly and lymphadenopathy on physical examination, and platelet response to classic ITP therapy. Review of the literature has shown case reports of disseminated histoplasmosis presenting with thrombocytopenia. Our patient comes from a geographic location where histoplasmosis is endemic. Most cases of histoplasmosis have mild symptoms and usually escape diagnosis. The microconidia formed in the mold phase of Histoplasma capsulatum are easily aerosolized, inhaled into the lungs, and then phagocytized by alveolar macrophages. Inside the macrophage, the organism converts to the yeast phase, survives within the macrophage for the first few weeks, and disseminates widely throughout the reticuloendothelial system. If cell-mediated immunity is deficient because of immunosuppression due to corticosteroids, transplanted organs, the organisms remain viable within macrophages and cause progressive infection. Most patients have either no symptoms or mild pulmonary complaints that are not severe enough to seek medical care. Although disseminated histoplasmosis has been reported to be associated with thrombocytopenia and anemia, most of these patients are immunocompromised. We report a case of ITP secondary to histoplasmosis in an immunocompetent patient.




J Med Cases. 2015;6(11):483-484
doi: http://dx.doi.org/10.14740/jmc2230w