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NTM Parotid — SCE Infectious Diseases MCQ

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HardTuberculosisNTM ParotidSCE Infectious Diseases

A 45-year-old man presents with a 3-month history of painless swelling of the right parotid gland. Fine needle aspirate shows granulomatous inflammation. AFB stain is negative. He has no risk factors for TB. He keeps tropical fish and has a fish tank at home. What atypical mycobacterium should be considered?

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Reveal the answer and explanation

Correct answer: E — Mycobacterium marinum (from fish tank water contaminating a facial wound or rarely causing parotid infection via haematogenous spread)

While M. marinum classically causes cutaneous infection from fish tank exposure, disseminated or unusual-site infection can rarely occur. However, this is a trick question — chronic parotid granulomatous inflammation with fish tank exposure should primarily raise suspicion for NTM generally. M. avium complex is the more common NTM cause of cervical lymphadenitis, particularly in children. The fish tank history is a distractor for M. marinum but the parotid location with granulomata is more suggestive of MAC or TB. Culture and PCR of the aspirate will identify the species.

Reference: BTS 2017 – NTM guidelines; NICE CKS 2024 – Lymphadenopathy