Disseminated tuberculosis with Poncet's disease mimicking childhood-onset systemic lupus erythematosus: a unique case report.

Disseminated tuberculosis in children may present with systemic and immunologic features that overlap with autoimmune diseases, complicating diagnosis and treatment. We report the first pediatric case of microbiologically confirmed disseminated tuberculosis involving multiple sites associated with Poncet's disease, mimicking childhood-onset systemic lupus erythematosus (cSLE). A previously healthy five-year-old boy presented with a four-month history of persistent fever, weight loss, and symmetrical oligoarthritis involving both knees and wrists, resulting in loss of mobility. Laboratory tests revealed severe non-hemolytic anemia, leukopenia, elevated inflammatory markers, hypoalbuminemia, hematuria, positive antinuclear antibodies, low complement levels, and lupus anticoagulant positivity. Chest imaging showed bilateral pleural effusion, pulmonary opacities, and lymphadenopathy, fulfilling the Systemic Lupus International Collaborating Clinics (SLICC) classification criteria for cSLE. Despite initially negative tuberculin skin test and gastric lavage analysis, lymph node biopsy confirmed Mycobacterium tuberculosis by histology, molecular assay, and culture. Subsequent urine and gastric samples were also positive. The patient had received BCG vaccination at birth. He was treated with rifampicin, isoniazid, pyrazinamide, and pyridoxine, with rapid clinical improvement, complete resolution of arthritis, and full recovery of mobility without sequelae in one month. No immunosuppressive therapy was administered. This case reinforces the diagnostic complexity of distinguishing tuberculosis from childhood-onset systemic autoimmune rheumatic diseases, particularly in endemic regions. To our knowledge, this is the first reported pediatric case of disseminated tuberculosis with Poncet's disease mimicking cSLE. Recognizing this specific condition is crucial to prevent misdiagnosis and unnecessary immunosuppression, while ensuring timely treatment of the underlying infection.