Tuberculous gumma associated with idiopathic thrombocytopenic purpura: report of a Japanese female patient

Our patient was a 77-year-old Japanese woman, who was under treatment for idiopathic thrombocytopenic purpura (ITP) and chronic renal failure. She had warm nodules and cord-like induration on her left knee that appeared similar to Bazin's erythema induratum. A chest X-ray examination revealed miliary tuberculosis; after anti-mycobacterial therapy, the warm nodules and cord-like induration were transformed into a cold, non-tender abscess that drained. Histopathological findings showed caseation necrosis in the subcutaneous tissue, however, mycobacteria were directly detected by Ziehl-Neelsen staining from cutaneous lesions, and cultures from the same lesion also grew Mycobacterium tuberculosis. Tuberculous gumma demonstrated multiple, cold, painless abscesses and thrombosis were also seen. This is a rare and unusual clinical form of cutaneous tuberculosis, and the result of hematogenous dissemination from a primary focus during periods of lowered resistance.