Mycobacterium simiae: a rare cause of cervical lymphadenitis—case report

Abstract: There are over 140 species of non-tuberculosis bacteria that cause a wide range of infections in the human host, with cervical lymphadenitis being the most common in immunocompetent children. Due to the slow growing nature of the species, this usually presents as a slowly-enlarging, non-tender unilateral swelling in the neck. We present the case of previously healthy 7-year-old indigenous female, who presented with a 3-month history of right sided, non-tender neck swelling, without systemic symptoms. Ultrasound demonstrated an enlarged right submandibular node and subsequent fine needle aspirate did not yield a microbiological diagnosis, thus she progressed to incision and drainage. Histology revealed necrotising granulomas, consistent with mycobacterial infection. Further stains and extended cultures did not yield a specific diagnosis. She was commenced on empiric therapy for Mycobacterium avium complex (MAC), however was lost to follow-up, before re-presenting with progressive neck swelling. The patient then underwent surgical excision of the node, and histology revealed chronic inflammation with non-necrotic granulomas, while polymerase chain reaction identified Mycobacterium simiae (M. simiae). The child recovered well, and at a follow-up review 5 months post operatively, the wound had healed well, with no palpable adenopathy present, and repeat ultrasound revealed only non-pathological small lymphadenopathy. This case demonstrates a rare cause of cervical lymphadenitis which was ultimately successfully treated with surgical resection; highlighting the challenges of both diagnosis and treatment of the pathogen given its multi-drug-resistant tendency.