The first Korean case of disseminated mycetoma caused by Nocardia pseudobrasiliensis in a patient on long-term corticosteroid therapy for the treatment of microscopic polyangiitis.

Nocardia pseudobrasiliensis is predominantly associated with invasive infections in immunocompromised patients. We report a case of disseminated mycetoma caused by N. pseudobrasiliensis in a 57-yr-old woman with microscopic polyangiitis, who was treated for 3 months with corticosteroids. The same organism was isolated from mycetoma cultures on the patient's scalp, right arm, and right leg. The phenotypic characteristics of the isolate were consistent with both Nocardia brasiliensis and N. pseudobrasiliensis, i.e., catalase and urease positivity, hydrolysis of esculin, gelatin, casein, hypoxanthine, and tyrosine, but no hydrolysis of xanthine. The isolate was identified as N. pseudobrasiliensis based on 16S rRNA and hsp65 gene sequencing. The patient was treated for 5 days with intravenous ampicillin/sulbactam, at which time both the mycetomas and fever had subsided and discharged on amoxicillin/clavulanate. This case highlights a very rare presentation of mainly cutaneous mycetoma caused by N. pseudobrasiliensis. This is the first reported case of N. pseudobrasiliensis infection in Korea.