Microsporidium-associated sinusitis.

Two cases of biopsy-proven Microsporidium-associated chronic sinusitis in HIV-seropositive patients are presented. Spores of Septata intestinalis were identified by light microscopy and confirmed by electron microscopy in each case. Both patients displayed severe deficiencies of nasal mucosa CD4-positive cells, demonstrated by immunohistochemical methods. Only two other cases of Septata intestinalis-associated sinusitis have been reported previously. Our observations agree with the theory that functional defects in local mucosal immunity may partially explain the acquisition of opportunistic mucosal infections in many HIV-seropositive patients.