Isolated Forearm Abscess with Bilateral Psoas Abscesses: An Unusual Presentation of Extrapulmonary Preextensively Drug-resistant Tuberculosis without Pulmonary Involvement.

Extrapulmonary tuberculosis (TB) accounts for 15%-20% of all TB, but soft-tissue involvement of the extremities is distinctly uncommon. Concurrent forearm and bilateral psoas abscesses from drug-resistant Mycobacterium tuberculosis, in a patient without pulmonary disease, have not - to our knowledge - been described. A 16-year-old immunocompetent girl reported right-sided chest pain, a progressively enlarging swelling on the left forearm, anorexia, and weight loss over roughly 2 weeks. Fever, cough, and night sweats were absent, as was any known TB contact. On examination, the forearm lesion was firm and nontender; bilateral lower-abdominal tenderness in the iliac fossae was the only abdominal finding. Cross-sectional imaging identified a solitary forearm abscess together with bilateral psoas collections; magnetic resonance imaging of the lumbosacral spine additionally revealed vertebral-body destruction and paravertebral soft-tissue involvement consistent with Pott's disease. Chest radiography was unremarkable. GeneXpert MTB/RIF performed on pus aspirated from both sites confirmed M. tuberculosis complex with rifampicin resistance; a line-probe assay subsequently documented additional resistance to isoniazid and fluoroquinolones - fulfilling the definition of preextensively drug-resistant (XDR) TB. An all-oral modified longer regimen comprising cycloserine, linezolid, clofazimine, bedaquiline, and delamanid was initiated, with steady clinical recovery. Pre-XDR TB may manifest as disseminated soft-tissue disease at unconventional sites - forearm and paravertebral musculature - even when the lungs are radiologically clear. Early molecular resistance testing on pus aspirates shortened the interval to appropriate second-line therapy and likely shaped the favourable trajectory observed here.