Malassezia, also known as Pityrosporum, are opportunistic yeasts that belong to the basidiomycetous yeasts. These lipophilic yeasts are constituents of the normal human skin flora composed of at least 14 species. They are responsible for a wide spectrum of clinical manifestations ranging from benign disease to systemic infections. In an immunocompromised state such as in diabetes mellitus, hematologic malignancies, or HIV, Pityrosporum can present in wide variety of cutaneous manifestations. (1,2)
Pityrosporum folliculitis was first described in 1969 by Weary & Cols and recognized clinically and histopathologically by Potter et. al in 1973. It usually presents as erythematous pruritic, monomorphic follicular papules and pustules, usually on upper back, chest, and shoulders. It is more common in tropical climates. Pityrosporum folliculitis is common in the Philippines and found to co-exist with acne vulgaris in 56% of patients. However, because of its presentation, it is frequently missed and thus is most frequently diagnosed on biopsy. ( 3,4,5,6)
Polycythemia vera is one of the chronic myeloproliferative neoplasms characterized mainly by an elevated absolute red blood cell mass because of uncontrolled red blood cell production with increased myeloid and platelet production, due to abnormal cloning of the hematopoietic stem cells with increased sensitivity to the different growth factors for maturation. Polycythemia vera is relatively rare, occurring in 0.6-1.6 persons per million population. The median age at diagnosis is approximately 60 years. Progenitors of the blood cells in these patients display abnormal responses to growth factors, suggesting the presence of a defect in a signaling pathway common to different growth factors. Currently, JAK2 is considered as the mutation involved in the intracellular signaling following exposure to cytokines causing hypermaturation. Ths genetic substitution, (JAK2V617) leads to a permanently turned-on signaling at the affected cytokine receptors. Its symptoms are usually due to sludging of blood flow and thrombosis leading to poor oxygen delivery due to a hyperviscous state such as headache, dizziness, chest pain and intermittent claudication. Splenomegaly is a common physical exam finding. ( 7,8)
While Pityrosporum folliculitis may occur in immunocompromised states, coexistence with polycythemia vera is a rare occurrence; to this date, there are no noted local or international published studies showing the co- existence of these 2 diseases hence the need to report this underecognized dermatologic condition in a patient with concurrent hematologic malignancy.