Histoplasma capsulatum

on 27.8.08 with 0 comments

  • common in the Midwest

  • associated with bird and bat droppings

  • asymptomatic infection is the rule

histoplasmosis typical case presentation

  • 60-yo farmer decides to move a small chicken house

  • several days later, develops fever, cough, SOB

  • reticulonodular pulmonary infiltrate with a moderate-to-severe illness and a prolonged recovery


  • fluffy white mold in culture

  • conidia show up as tubercles/spikes on the mycelia

  • the actual infectious form is the microconidia


  • silver stain: the fungi are dividing inside macrophages

  • punctate appearance inside the macrophages

  • PAS stain: narrow-neck budding of fungi

geographical distribution

  • most intensely endemic around the Ohio river valley—states include OH, TN, AK, IN

  • however, you can get it anywhere in the South or in Texas

  • you can get it even in CA, though this is very uncommon

endemic in the Americas

  • not as highly endemic in Central and South America, but still endemic

clinical manifestations

  • acute pulmonary

  • chronic pulmonary

  • disseminated

  • fibrosing mediastinitis (very rare)

disseminated disease

  • occurs primarily in the immunocompromised

  • most commonly, GI tract, miliary disease, spleen, liver, adrenal glands, CNS

mucocutaneous dissemination

  • tongue lesion

  • ankle lesion

GI dissemination

  • look like bowel cancers on X-ray

  • upon scoping, trabeculated lesions

disseminated histo

  • immunosuppression is already present in 2/3 of those affected

    • steroids, 1970s

    • AIDS, 1980s

    • TNF inhibitors for Rx arthritis, 2000s

  • FUO (fever of unknown origin)

  • RE tissues

  • focal lesions

detection of circulating antigen in the urine

  • second-generation antigen test is more predictive than the old one

  • more true positives, fewer false negatives

histology of a lung from a patient on Etanercept, a TNF inhibitor

  • diffuse pulmonary infiltrate

  • the infection is very uncommonly seen here in SD, but very common in the central and eastern US

Category: Microbiology Notes



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