A 4-year-old child has a slowly enlarging, painless, unilateral cervical lymph node mass for two months. There is no fever, the chest radiograph is normal, and the Mantoux test is 6 mm. Excision biopsy shows caseating granulomas, and culture grows colonies that are pigmented yellow even when incubated away from light. Which organism is most likely?

• A Mycobacterium tuberculosis
• B Mycobacterium ulcerans
• C Mycobacterium kansasii
• D Mycobacterium scrofulaceum ✓

Explanation

Scrofula in young children is classically caused by nontuberculous mycobacteria, especially M. scrofulaceum, acquired through the oropharynx and involving submandibular or high cervical nodes without systemic features. M. scrofulaceum is a scotochromogen (Runyon group II), producing yellow pigment in the dark. Cervical tuberculosis from M. tuberculosis is more typical of adults, involves lower jugular nodes, and is accompanied by constitutional symptoms.

Reference: Nelson Textbook of Pediatrics, 22nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.