Histoplasmosis: a Clinical and Laboratory Update

Abstract

SUMMARY Infection with Histoplasma capsulatum occurs commonly in areas in the Midwestern United States and Central America, but symptomatic disease requiring medical care is manifest in very few patients. The extent of disease depends on the number of conidia inhaled and the function of the host's cellular immune system. Pulmonary infection is the primary manifestation of histoplasmosis, varying from mild pneumonitis to severe acute respiratory distress syndrome. In those with emphysema, a chronic progressive form of histoplasmosis can ensue. Dissemination of H. capsulatum within macrophages is common and becomes symptomatic primarily in patients with defects in cellular immunity. The spectrum of disseminated infection includes acute, severe, life-threatening sepsis and chronic, slowly progressive infection. Diagnostic accuracy has improved greatly with the use of an assay for Histoplasma antigen in the urine; serology remains useful for certain forms of histoplasmosis, and culture is the ultimate confirming diagnostic test. Classically, histoplasmosis has been treated with long courses of amphotericin B. Today, amphotericin B is rarely used except for severe infection and then only for a few weeks, followed by azole therapy. Itraconazole is the azole of choice following initial amphotericin B treatment and for primary treatment of mild to moderate histoplasmosis.

Histoplasmosis en Colombia: resultados de la encuesta nacional, 1992-2008

“…A significant difference, p=0.01, was found between AIDS and non-AIDS patients, a difference already noticed in other reports and considered to be connected to the seriousness of the disease course in HIV patients (2,4,5,31,(37)(38)(39). The advanced stage of the latter infection in this series explains the clinical behavior of the mycosis, as observed by the lesser age found in this group as compared with those in the other risk factor groups; it may also explain, partially at least, the observed sex differences although here a more intense environmental exposure is also attributed to males.…”

“…Besides presenting a more rapid course, the clinical course of the AIDS patients was also more aggressive and exhibited peculiar characteristics rarely informed in other patients groups, such as indicated by hematologic abnormalities and frequency and severity of skin lesions, as described earlier (2,4,5,31,(37)(38)(39). It should be noticed that skin lesions are seldom observed in North American patients (8,9).…”

“…Also of importance was the number of patients (23.2%) in whom no lung radiographic abnormalities were detected, a finding that indicates that X-ray exams are not as reliable as expected. Probably other image studies, such as CAT and MRI would detect the primary lung lesions (1,2,4,5).…”

“…On the contrary, in immunocompromised individuals, such infections are not only severe but result in progressive disease with hematogenous dissemination and a variety of clinical manifestations. Any organ can be affected, especially lungs, bone marrow, skin, brain, adrenal glands, and the gastrointestinal tract (4,5).…”

Necrotizing granulomatous inflammation: what does it mean if your special stains are negative?

“…11 Real-time PCR for Histoplasma is available but requires fresh frozen tissue. 12 For mycobacteria, detection of these small and few microorganisms on conventional ZN is a real issue and screening may be laborious. Searching for a method to facilitate screening, Dr Tadrous reported an automatic screening algorithm using digital image analysis.…”