Histoplasmosis

Japanese: ヒストプラズマ症

(2) Histoplasmosis
Histoplasmosis is the most important imported mycosis along with coccidioidomycosis. The causative agent is the dimorphic fungus Histoplasma capsulatum, which is classified into the capsulatum type and the zovoaji type depending on the species. Endemic areas are widespread, with the former often found in North and South America and Southeast Asia, and the latter in Africa. In both cases, infection is caused by inhalation of conidia. The incubation period for the capsulatum type is usually 1-4 weeks, but relapses after initial infection are common. It is an intracellular parasite that disseminates from the lungs to various organs, such as the reticuloendothelial system in the liver, spleen, and bone marrow, as well as to the adrenal glands and prostate. Chest X-rays show diffuse granular shadows, nodular shadows, hilar lymphadenopathy, pleural effusion (acute pulmonary histoplasmosis), infiltrative shadows, fibrosis, and cavities (chronic). Disseminated cases are characterized by hepatosplenomegaly, anemia, and mucosal ulcers. Risk factors include impaired cellular immunity (AIDS, steroid administration, etc.). The fatality rate is particularly high in those with underlying conditions. Diagnosis is by culturing and identifying the fungus, histopathological examination, and serological tests (antigen and antibody detection). In the Zvoaji type, lesions form mainly in the subcutaneous tissue, and there is little dissemination to deeper organs. Treatment involves the administration of antifungal drugs (azole drugs, mainly amphotericin B and itraconazole). [Kamei Katsuhiko]

Source : Internal Medicine, 10th Edition About Internal Medicine, 10th Edition Information

Japanese:

（2）ヒストプラズマ症（histoplasmosis）
　コクシジオイデス症と並んで最も重要な輸入真菌症である．原因菌は二形性真菌のHistoplasma capsulatumであるが，菌種によりカプスラーツム型とズボアジ型とに分類される．流行地域は広汎で，前者は南北アメリカ，東南アジアなど，後者はアフリカでしばしばみられる．いずれも分生子の吸入により感染する．カプスラーツム型では潜伏期は通常1～4週間とされるが，初感染後の再燃も多い．細胞内寄生菌であり，肺から肝，脾，骨髄などの細網内皮系や副腎，前立腺などの諸臓器に播種する．胸部X線写真ではびまん性粒状影，結節影，肺門リンパ節腫脹，胸水貯留（急性肺ヒストプラズマ症），浸潤影，線維化，空洞などが認められる（慢性）．播種性では肝脾腫，貧血，粘膜潰瘍などを呈する．危険因子として，細胞性免疫障害（AIDSや，ステロイド投与など）がある．基礎疾患のある場合は特に致命率が高い．診断は菌の培養・同定，病理組織学的検査，血清検査（抗原・抗体検出）などにより行う．ズボアジ型では皮下組織を中心として病変を形成し深部臓器への播種は少ない．治療は抗真菌薬（アムホテリシンB，イトラコナゾールを中心としたアゾール薬）の投与を行う．［亀井克彦］

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