Grand Rounds

Twins with Tuberculous Abscesses in the Left Thigh Vaccination Site - Is it BCG or Mycobacterium Tuberculosis?

Dhruv Gandhi, Aditi Gupta, Shatakshi Garg, Zahabiya Nalwalla, Ira Shah
Pediatric State DR- TB Centre of Excellence, Department of Pediatric Infectious Diseases, BJ Wadia Hospital for Children, Mumbai, India

Address for Correspondence: Dr Dhruv Gandhi, 5B/13 Shyam Niwas, Breach Candy, Mumbai-400026, Maharashtra, India. Email: dhruvgandhi2610@gmail.com

Keywords: cold abscess, TB Thigh abscess, BCG vaccine, injection site abscess, AEFI, BCG abscess

Clinical Problem:
Patient 1, a 3-month-old girl, born preterm in March 2024 at 34 weeks and 4 days with a birth weight of 1.9 kg, was the first-born twin. She was admitted to the neonatal intensive care unit (NICU) for 10 days due to neonatal hyperbilirubinemia (NNH). She received the Bacillus Calmette-Guérin (BCG) and Hepatitis B vaccines 3 weeks after birth. She presented in June 2024 with a painful, erythematous lump over the left thigh injection site, first noticed 1 month post-vaccination. There is no history of tuberculosis (TB) contact. On presentation, her weight was 3.71 kg (below 3^rd percentile as per Indian Academy of Pediatrics (IAP) growth charts). On examination, a tender, mildly erythematous swelling was present in the left thigh with mild purulent oozing. No scar was seen over the left deltoid. Other general and systemic examinations were normal. Thigh ultrasound (USG) showed a thick, irregularly walled collection in the intramuscular plane measuring 2.1x1.8x1.4 cm containing 2.8 mL of fluid showing moving internal echoes, suggestive of an abscess. She was given oral amoxicillin-clavulanic acid for 5 days. A repeat USG found 2.3 mL of fluid. USG-guided drainage was done following which the volume reduced to 0.3 mL. She was discharged on oral linezolid for 12 days. Pus sent for Xpert MTB/RIF detected Mycobacterium tuberculosis complex (MTBC) and reported it as rifampicin sensitive. Other investigations are shown in Table 1. She was prescribed a local betadine ointment and was asked to follow-up with a repeat USG.

Patient 2, a 3-month-old girl, was the second-born twin with birth weight of 1.75 kg. She was also admitted to the NICU for 10 days due to NNH. She also received the BCG and Hepatitis B vaccines 3 weeks after birth. She presented in June 2024 with a painful lump over the left thigh injection site, first noticed 1 month post-vaccination. On presentation, her weight was 3.7 kg (below 3^rd percentile as per IAP growth charts). On examination, a tender, warm swelling was present in the left thigh measuring approximately 1.5 x 1 cm with a pus point. Other general and systemic examinations were normal. Thigh USG showed a thick, irregularly walled collection in the intramuscular plane measuring 2.8x2.0x1.3 cm containing 4.0 mL of fluid showing moving internal echoes, suggestive of an abscess. USG-guided drainage was done and the pus sent for Xpert MTB/RIF which detected MTBC and reported it as rifampicin sensitive. She was also discharged on oral linezolid for 12 days. Other investigations are shown in Table 1. A follow-up USG showed 3.6 mL of fluid. She was advised another USG-guided drainage and asked to follow-up one week post-procedure.

Table 1. Investigations of the patient.

Investigations	Patient 1	Patient 2	Reference Range
Hemoglobin (gm/dL)	9.2	10.1	11.5-15.5
White blood cell count (cells/cumm)	10,590	26,220	5000-13,000
Absolute neutrophil count (cells/cumm)	5546	10,795	2000-8000
Absolute lymphocyte count (cells/cumm)	4080	12,902	1000-5000
Platelets (106 cells/cumm)	5.50	5.96	1.50-4.50
C-reactive protein (CRP) (mg/L)	1.39	4.88	<3.00
Blood culture	No growth	No growth	-
Aerobic pus culture	No growth	No growth	-
Anaerobic pus culture	No growth	No growth	-

Should the twins be started on anti-tubercular therapy (ATT)? Why was MTBC detected from the injection sites?