Disseminated Sphingomonas paucimobilis Infection Mimicking Tuberculosis in a Patient With Type 3c Diabetes: Case Report

Sphingomonas paucimobilis is a rare opportunistic gram-negative bacillus increasingly reported in immunocompromised individuals. A 45-year-old male presented with right cervical swelling, fever, weight loss, anorexia, jaundice, and a discharging cervical sinus for two weeks. Examination revealed tachycardia, tachypnoea, pallor, icterus, cervical lymphadenopathy with sinus discharge, hepatosplenomegaly, and left-sided chest crepitations. Investigations showed neutrophilic leucocytosis, elevated C-reactive protein (CRP), deranged liver and renal function tests, and uncontrolled diabetes mellitus. Imaging demonstrated necrotic cervical lymphadenopathy, chronic calcific pancreatitis, and multiple bilateral pulmonary nodules with ground-glass opacities. Pus examination was negative for acid-fast bacilli, fungal elements, and a cartridge-based nucleic acid amplification test (CBNAAT) for tuberculosis; however, repeated cultures isolated Sphingomonas paucimobilis. Fine-needle aspiration cytology (FNAC) from a pulmonary nodule showed no malignancy and negative CBNAAT. The patient demonstrated marked clinical, laboratory, and radiological improvement with culture-guided piperacillin-tazobactam therapy and optimal glycaemic control. This case underscores the need to consider rare opportunistic infections as important differentials of disseminated tuberculosis.