Metastatic tuberculous abscess caused by Mycobacterium bovis presenting as subcutaneous nodules in a woman with rheumatoid arthritis

Abstract

A metastatic tuberculous abscess is a rare condition that should be considered in the differential diagnoses of subcutaneous nodules in immunosuppressed patients. A 71-year-old woman with rheumatoid arthritis developed disseminated tuberculosis due to Mycobacterium bovis. After taking a vertebral biopsy, subcutaneous nodules appeared on the extremities. Initial histopathological and microbiological studies performed on the skin biopsy did not identify the mycobacterium. An aspirate obtained from a cold abscess was cultured and studied with a positive polymerase chain reaction; cultures grew M. bovis and treatment for disseminated tuberculosis was initiated. Two months later, the fevers recurred, and new skin nodules appeared. A repeated skin biopsy failed to identify the agent, yet it again grew from the material obtained from an aspirated abscess. Diagnostic tests should be exhausted in order to identify the organism successfully. This case suggested that recurrent hematogenous dissemination may originate after the manipulation of deep foci and present as a metastatic tuberculous abscess. Key words: Mycobacterium bovis; Cutaneous tuberculosis; Vertebral tuberculosis; Metastatic tuberculous abscess; Immunosuppression