Human histoplasmosis is caused by 2 varieties of Histoplasma. The most common variety worldwide is H. capsulatum var. capsulatum, which has been reported from many disease-endemic areas where HIV infection is prevalent. Histoplasmosis is more frequent in the United States (Ohio and Mississippi River valleys), but it is not unusual in other parts of the world, such as Africa ( 1 , 2 ). In the western and central regions of sub-Saharian Africa, H. capsulatum var. capulatum coexists with another variety, H. capsulatum var. duboisii, whose ecology and pathogenesis remain almost unknown. Cases due to H. capsulatum var. duboisii are scarce in Europe, and all are imported ( 3 ). Before the era of highly-active antiretroviral therapy (HAART), the prevalence of H. capsulatum var. capsulatum infections reached up to 30% of HIV-infected patients in hyperendemic areas of the southeastern part of the United States ( 4 ). The infection occurs more often in patients with a CD4 count 200/mm3 and undetectable viral load). In July 2007, she is doing well with a CD4 count of 700/mm3 and a still-undetectable viral load. Discussion H. capsulatum var. duboisii is also known as African histoplasmosis because it has only been described on that continent, mostly in central and western Africa. The prevalence of histoplasmosis due to variety duboisii has not been established in countries in these regions in HIV-negative patients. Fewer than 300 cases are reported in the literature ( 7 ). The reason it remains rare, despite the major HIV pandemic in Africa, is unknown. Potential explanations are that patients die from other causes before histoplasmosis develops ( 8 ) or that variety capsulatum is more virulent than variety duboisii. This situation is reminiscent of Cryptococcus gattii and C. neoformans. C. gattii is rarely identified in HIV-infected patients, in contrast with C. neoformans, whereas both are present in the environment in countries where the prevalence of HIV infection is high ( 9 ). However, variety capsulatum is frequent in Africa. No data on the relative frequency of those 2 varieties has been published. Skin reaction to histoplasmin in histoplasmosis-endemic areas showed a 3% prevalence ( 10 ), but variety capsulatum and variety duboisii were not able to be differentiated. Higher prevalence (≈35%) was found in rural populations, especially among farmers, traders, and cave guides ( 11 ). Histoplasmosis due to variety duboisii may be misdiagnosed in those areas because of physicians’ lack of awareness. The pathogenesis of African histoplasmosis remains unclear. The main route of acquisition could be airborne contamination from the soil, rarely direct inoculation. Variety duboisii is classically associated with cutaneous lesions (nodules, ulcers) and osteolytic bone lesions, especially affecting the skull, ribs, and vertebrae (Table 1) ( 12 , 13 ). Histopathologic examination shows granuloma with necrosis and suppuration. Disseminated disease is not uncommon and can involve every organ; however, the heart and central nervous system are unusual locations. A total of 17 cases have been reported thus far among HIV-infected patients, including the 3 cases described here ( 14 – 19 ). An additional case has been reported, but without detailed description, in a Ugandan patient diagnosed in Japan ( 20 ). Among the well-described cases (Table 1), most involved patients with poor immunologic status (mean CD4 count 55/mm3), which also occurs with histoplasmosis due to variety capsulatum ( 21 ). Most patients had disseminated infections, and only 4 patients died. The prognosis of disseminated infection in this context is close to the 20% mortality rate reported for disseminated histoplasmosis due to variety capsulatum among AIDS patients ( 21 ), but the few number of cases does not allow us to extrapolate the mortality rate related to variety duboisii. Epidemiologic information, clinical manifestations, and outcomes of immunocompetent versus HIV-infected patients infected with variety duboisii are compared in Table 2 ( 13 ). These data confirm the tropism of variety duboisii for lymph nodes, skin, and bones. It is noteworthy that the disease is often located in the lungs in HIV-negative patients, whereas HIV-infected patients have substantially more disseminated disease. The latter finding may be explained by immunodepression, poor access to the healthcare system for HIV-infected persons in Africa, and late diagnoses of histoplasmosis. Table 1 Description of HIV-infected patients with histoplasmosis due to Histoplasma capsulatum var. duboisii* Case no.† Age, y Sex Country Clinical findings CD4 count/mm3 Pathology Positive fungal culture Treatment Outcome 1 20 F Congo Skin lesions NR Skin – AmB 1 mg/kg/d, Itr 300 mg/d Relapse 2 44 M Congo Skin lesions, weight loss, lymph nodes, peritonitis NR Skin, pus – Ketoconazole 600 mg/d, AmB, Itr 300 mg/d Relapse 3 41 M Congo Skin lesions, weight loss, lymph nodes, hepatomegaly, splenomegaly NR Skin – AmB Death 4 65 M DRC Fever, weight loss, anemia NR Bone marrow Bone marrow, blood AmB Death 5 28 M DRC Fever, skin lesions, lymph nodes, weight loss, bone lesions NR Skin Skin Ketoconazole 600 mg/d NR 6 31 F Cameroon Septic shock 2 Bone marrow Bone marrow, blood ABLC 5 mg/kg/d, Itr 400 mg/d No relapse 7 29 M Liberia Skin lesions NR Skin Skin Itr 200 mg/d NR 8 43 F Guinea-Bissau Fever, weight loss, anemia, abdominal pain 68 Colon – Itr 400 mg/d No relapse 9 30 M Nigeria Fever, skin lesions, lymph nodes, anemia 2 Skin Skin AmB 1 mg/kg/d, Itr 400 mg/d Relapse 10 38 M DRC Fever, weight loss, lymph nodes 160 Lymph nodes Bone marrow, lymph nodes AmB No relapse 11 26 M Congo Fever, skin lesions, lymph nodes NR Lymph nodes – AmB 1 mg/kg/48 h No relapse 12 30 M Côte d’Ivoire Fever, weight loss, lymph nodes 6 Bone marrow – Itr 400 mg/d No relapse 13 50 F Nigeria Skin lesions, bone lesions NR Skin, bone – Fluconazole 100 mg/d No relapse 14 45 M Ghana Fever, weight loss, splenomegaly 24 Blood – AmB 0.7 mg/kg/d Death 15 37 M DRC Fever, lymph nodes 100 Lymph nodes – Itr 400 mg/d Death 16 41 M DRC Lymph nodes, skin lesions 50 Lymph nodes Lymph nodes Liposomal AmB, Itr 400 mg/d No relapse 17 2 F DRC Fever, skin lesions, bone lesions, blood 45 Skin, bone, blood Skin Liposomal AmB, fluconazole No relapse *NR, not reported; AmB, amphotericin B deoxycholate; Itr, itraconazole; DRC, Democratic Republic of Congo; ABLC, amphotericin B lipid complex.
†Cases 1–14 are from the literature review; cases 15–17 are personal cases; see text. Table 2 Comparison of clinical and microbiologic findings of HIV-infected and immunocompetent patients with histoplasmosis due to variety duboisii*† Characteristic HIV positive (n = 17) HIV negative (n = 20) Age, y (range) 35 (2–65) 34 (8–62) Sex (M:F) 12:5 19:1 Visceral localizations Lymph nodes 53 65 Skin 59 40 Bones 18 25 Lungs 0† 35† Gastrointestinal 12 5 Disseminated 85† 55† Clinical manifestations Fever 58† 15† Weight loss, asthenia, anorexia 54 30 Respiratory symptoms 0 20 Hepatosplenomegaly 12 15 Diagnosis sites Lymph nodes 24 45 Skin 48 35 Bone marrow 18 0 Bone 12 5 Gastrointestinal 6 5 Pus 6 25 Lung 0† 25† Mycologic diagnosis Direct examination 100 40 Culture 64 65 Blood culture 12 0 Treatment Amphotericin B 66 80 Ketoconazole 12 35 Itraconazole 64 20 Fluconazole 12 0 Outcome Relapse 12 40 Death 24 5 *Except where indicated, all values are percentages. HIV-negative patients are from Dupont et al. ( 13 ).
†p 200/mm3. The stability of immune improvement has to be confirmed for several months before prophylaxis is stopped ( 32 ). Recent data suggest that the risk for relapse is rare after 12 months of treatment with a sustained immunologic improvement (CD4 >150/mm3) ( 33 ). However, in our experience based on the management of 20 cases of histoplasmosis due to variety duboisii in patients considered immunocompetent ( 13 ), relapses may be observed several years after the first episode. Thus, prolonged follow-up is mandatory for every patient with histoplasmosis due to variety duboisii. Since HAART was introduced, the clinical and immunologic conditions of HIV-infected patients have dramatically improved, but physicians should now be aware of immune reconstitution inflammatory syndrome (IRIS) ( 34 ). As for many pathogens, both varieties of H. capsulatum can induce IRIS in HIV-infected patients, as recently reported by our group ( 6 ). The importance of the inflammatory reaction during IRIS contrasts with the mild one observed in the initial phase of the disease in severely immunocompromised patients and may require specific treatment. Thus, histoplasmosis due to variety duboisii in HIV-infected patient remains a rare clinical entity but diagnosis should not be discounted because of the HIV status of the patient. Physicians working in Africa should be aware of H. capsulatum var. duboisii as a potentially emerging infection in HIV-infected patients.