in november 2005 , a 78-year - old man with underlying rheumatoid arthritis was sent to the emergency department with generalized weakness and poor appetite of several weeks duration . he had received oral therapy with prednisolone ( 5 mg twice per day ) , hydroxychloroquine ( 200 mg twice per day ) , sulfasalazine ( 1,000 mg twice per day ) , and methotrexate ( mtx ) ( 15 mg per week ) for 4 months . the patient s body temperature was 38.5c , blood pressure was 129/80 mm hg , pulse rate was 76 beats / min , and respiratory rate was 20 breaths / min . a complete blood cell count showed a leukocyte count of 6,110/l ( 4% bands , 77% segmented neutrophils , 7% lymphocytes , 6% normoblasts , and 3% myelocytes ) , hemoglobin level of 11.5 g / dl , and platelet count of 3,000/l . biochemical testing showed total bilirubin level of 3.89 mg / dl ( normal 01.3 mg / dl ) and alkaline phosphatase level of 480 u / l ( 60220 u / l ) . the rheumatoid factor level was 76.3 iu / ml ( normal < 15 iu / ml ) . the erythrocyte sedimentation rate and c - reactive protein level were 30 mm / hour ( 020 mm / hour ) and 100 mg / l ( 05 mg / l ) , respectively . the patient was admitted with the tentative diagnosis of mtx - induced thrombocytopenia . bone marrow aspiration ( figure 1 ) and biopsy were performed because of refractory thrombocytopenia and the presence of young blood cells on the peripheral blood smears . intravenous amphotericin b ( 0.7 mg / kg / day ) was administered because disseminated histoplasmosis was highly suspected because of the bone marrow findings . four weeks later , the fungal culture of the bone marrow showed growth of mold ( figure 2a and b ) . the microorganism was subsequently identified as h. capsulatum by pcr assay ( figure 2c ) ( 8) . bone marrow examination of patient a bone marrow biopsy specimen showing numerous oval - shaped intracellular and extracellular microorganisms ( a and b ) . a bone marrow aspiration smear showed numerous intracellular yeastlike microorganisms ( c and d ) . schiff stain , 1,000 ; c ) , gram stain , 1,000 ; and d ) , wright stain , 1,000. a ) colony of the mold from the patient is white - brown with a cottony appearance on sabouraud dextrose agar . b ) lactophenol cotton blue stain ( hardy diagnostics , santa maria , ca , usa ) of the isolated mold showing thick - walled and tuberculate macroconidia ( arrowheads ) and microconidia ( arrows ) . c ) pcr assay for identification of histoplasma capsulatum based on the nucleotide sequence of the m antigen . pcr products included 111-bp and 279-bp fragments amplified with primers msp1f - msp1r ( pair 1 ) and msp2f - msp2r ( pair 2 ) , respectively , which confirmed the identification of h. capsulatum ( 8) . the patient s general condition improved after administration of a total dose of 1 g of intravenous amphotericin b , and the patient was discharged and treated with oral itraconazole , 200 mg once a day . the patient was closely monitored for 3 months , and no clinical evidence of histoplasmosis relapse was noted . a variety of laboratory tests for diagnosis of histoplasmosis , including fungal culture , histopathology , serologic tests , antigen detection , and molecular methods , have different sensitivities based on clinical manifestations and host status ( 9 ) . however , it usually requires 4 weeks to grow and has a low sensitivity rate ( 15% ) in self - limited histoplasmosis . the knobby appearance of macroconidia and microconidia indicated by lactophenol cotton blue stain ( hardy diagnostics , santa maria , ca , usa ) of the mold form from fungal cultures is characteristic of h. capsulatum ( figure 2b ) ( 10 ) . in histopathology , histoplasmosis is impressive , with its numerous ovoid - shaped microorganisms in infected tissue ( figure 1 ) . however , without sufficient experience , one could misidentify blastomyces dermatidis , candida glabrata , cryptococcus neoformans , penicillium marneffei , leishmania spp . , pneumocystis jirovecii , or toxoplasma gondii as h. capsulatum ( 11 ) . despite a characteristic form , specific dna probing is usually applied for faster definitive identification ( 12 ) . in areas where histoplasmosis is not endemic , including taiwan , serologic tests , antigen detection reagents , and specific dna probes for diagnosis of histoplasmosis are not universally available . among serologic tests , immunodiffusion and complement fixation for anti histoplasma antibody detection are widely applied ; sensitivity rates are 95%100% and 82%90% for pulmonary and disseminated histoplasmosis , respectively . some limitations occur , including the need for 2 to 6 weeks for antibody production after infection , impaired production of antibodies in immunosuppressed patients , and presence of cross - reaction mainly due to paracoccidioidomycosis , blastomycosis , and aspergillosis ( 9 ) . antigen detection in serum and urine is the most useful method of diagnosing histoplasmosis because it provides early diagnosis before culture and antibody production , monitors response of therapy , and detects relapse . the sensitivity rates of antigen detected are 25%75% in pulmonary histoplasmosis and 82%95% in disseminated histoplasmosis . cross - reactions may occur in cases of paracoccidioidomycosis , blastomycosis , african histoplasmosis , and p. marneffei ( 9 ) . although the environment in taiwan is suitable for h. capsulatum to grow , histoplasmosis has been rarely encountered . in a survey of histoplasmin skin tests conducted in taiwan in the 1950s , only 7 ( 0.19% ) of 3,589 schoolchildren tested positive , and the author concluded histoplasmosis probably does not exist in taiwan or is very rare ( 13 ) . the first possible case of histoplasmosis in taiwan was reported in 1977 ; however , the diagnosis was doubtful because it was based only on histopathologic findings in a cervical lymph node biopsy specimen , without definitive fungal culture or molecular identification ( 2 ) . no further cases of histoplasmosis were reported in taiwan until this decade , when 6 cases were reported ( 37 ) . all cases include a history of travel or residence outside taiwan , where the patients might have acquired the infection ; furthermore , most of the patients had underlying hiv infections . diagnoses were mostly based only on histopathologic or morphologic findings in fungal cultures because the serologic tests , antigen detection reagents , and commercial dna probes for diagnosis of histoplasmosis were not available in taiwan . in contrast to these cases , our patient had never traveled outside taiwan and did not have an hiv infection . to confirm the identification of h. capsulatum on the basis of histopathologic and fungal form findings ( figures 1 , 2a , and 2b ) , we applied a specific pcr assay as previously described ( 8) , and the results were definitive ( figure 2c ) . the fibrocalcific nodules found on the chest radiograph imply that either 1 ) the patient might have had histoplasmosis for years and it became disseminated because of immunosuppressive therapy for rheumatoid arthritis or 2 ) the patient was reinfected with the calcified lesions that resulted from prior histoplasmosis . the results indicate that this is the first definitive indigenous case of disseminated histoplasmosis in taiwan . nonetheless , we were unable to monitor our patient s response to treatment by antigen tests , as is recommended ( 9,14 ) , because they are not available in taiwan . first , the diagnostic rate of histoplasmosis might be markedly decreased because of the lack of serologic and antigen testing kits and reagents , which are useful for diagnosis of self - limited and nondisseminated histoplasmosis . second , pulmonary histoplasmosis might be misdiagnosed as tuberculosis , which is prevalent in taiwan . third , physicians are unfamiliar with histoplasmosis and may consider that histoplasmosis is absent in taiwan . with increasing immunocompromised hosts resulting from immunosuppressive therapy and hiv infections , as well as improved diagnostic tests , histoplasmosis might be an emergent infectious disease in taiwan in the future . in summary , although an indigenous case of histoplasmosis had never been encountered , it should be 1 of the differential diagnoses of opportunistic infections in immunocompromised patients in taiwan . endemic regions might be underestimated because of the paucity of diagnostic tools and familiarity with histoplasmosis .
we report the first indigenous case of disseminated histoplasmosis in taiwan diagnosed by histopathology of bone marrow , microbiologic morphology , and pcr assay of the isolated fungus . 
 this case suggests that histoplasmosis should be 1 of the differential diagnoses of opportunistic infections in immunocompromised patients in taiwan .