Bacillus Calmette-Guérin (BCG) is a live attenuated vaccine prepared from Mycobacterium bovis with residual virulence to protect against tuberculosis (TB). It was first developed by Calmette and Guérin and approved for human use in 1921. This was the only vaccine against TB and is included as part of the routine immunization schedule in India¹. BCG adenitis is a common complication of its vaccination, which occurs in infants aged 3 months or older and usually persists until 6 weeks after vaccination². This occurs as a response to the BCG vaccine, causing the enlargement of the regional lymph nodes, with major involvement of the axillary (armpit) or supraclavicular (neck) nodes. These lymph nodes enlarge to their maximum size at around 3 months of age, and it is not a cause for alarm unless there is softening or cold abscess formation. This is a self-resolving condition, so no active inter- ventions are required².

Herein, we report an interesting case of persistent non- suppurative adenitis in a baby with an immunocompetent status, who presented with axillary adenitis even after the age of 1.5 years.

Figure 1. Left axillary lymph node measuring 2.5 × 2.0 cm

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Figure 2. Surgical excision of the axillary node

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Figure 3. Epithelioid cell granuloma lesion

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Figure 4. GeneXpert report

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A 5-month-old boy was brought by his parents to the pediatrician, with complaints of left axillary swelling for the past 2 weeks. He had BCG vaccination at birth, and his parents gave a history suggestive of the usual BCG reaction leading to a scar formation at the vaccination site. He had no history of contact with individuals diagnosed with TB. The patient had adequate weight gain for age and was on exclusive breast feeding, which was planned until 6 months of age. The developmental milestones were normal for his age.

On examination, the infant was active and alert and had a significantly enlarged left axillary lymph node measuring 2.5 × 2 cm, which was not tender, moderately mobile, and not fixed to underlying structures or skin, which was con- firmed by ultrasonography. The parents were counseled on the benign, self-limiting nature of the nodes and were asked to review if it had progressed or remained unresolved by the child's first birthday. On follow-up on his first birthday, the infant was healthy; however, the axillary node remained with no complications. This worried the parents, who were counseled again for observation and advised to follow-up every 3 months to check for progression or complications.

At the 18-month follow-up, the size of the left axillary lymph node was the same, with no complications, as confirmed by sonographic imaging. The parents insisted on the removal of the node. Thus, after the surgical consultation, the child underwent an excisional biopsy of the node. The node was excised and sent for HPE examination, Gram staining, acid-fast bacilli (AFB) staining, and GeneXpert for Mycobacterium tuberculosis (MTB).

The Ziehl-Neelsen staining was non-contributory, and the GeneXpert was positive for MTB. HPE showed epithelioid cell granulomatous lesions, with no AFB or necrosis, which was suggestive of BCG adenitis.

The BCG vaccine is one of the oldest vaccines used in humans, which has been used for the past 80 years and is one of the most widely used vaccines. Globally, approxi- mately 80% of the infants from developing nations have been covered under national immunization programs. This vaccine has shown a protective effect against disseminated, extrapulmonary, and meningeal TB in children. BCG does not provide protection against primary TB, latent pulmonary infection, and reactivation³.

Under normal circumstances, after vaccination, intradermally over the left deltoid, the BCG starts to spread or disseminate to various parts of the body, including the regional lymph nodes, causing asymptomatic lymphadenopathy. This lymph node enlargement has no clinical significance and resolves on its own over several weeks⁴. After BCG vaccination, the first reaction is an induration at the injection site, followed by ulceration and crust formation, which often settles down by 6~8 weeks, leaving a scar at the vaccination site; hence, an axillary lymph node enlargement <1 cm can be a normal response following vaccination⁵.

The diagnosis of BCG lymphadenitis is clinical. A few diagnostic markers include the following:

1. An ipsilateral swelling in the vaccinated site and absence of other medical cause for lymphadenitis⁶.

2. Absence of fever, tenderness, and other constitutional symptoms differentiating it from pyogenic adenitis.

3. Matted and enlarged discrete lymph nodes, which cannot be differentiated from tubercular lymphadenitis in histo- pathology studies.

Lymphadenitis is a side effect of BCG vaccination in neonates, which may be either related to the host or vaccine⁶. Other vaccine-related factors are as follows:

a) Vaccine strain used

b) Vaccination technique

c) Vaccine dose

d) Immune status of the child and its physique

Axillary lymph node enlargement was seen in 75% the vaccinees on the ipsilateral side (unilaterally), and this is con- sistent with the presented case8.

Teo et al. reported an increase in BCG-related lymphadenitis after the use of the Danish strain (SSI) type⁸. This correlates with the current case because the same strain of vaccine was used in our patient. Complications range from mild to disseminated BCG infections, between regional lymphadenitis to suppurative lymphadenitis, osteomyelitis, and disseminated BCG infections⁹.

In the current case, such disseminated infections after BCG vaccination are rare, and isolated enlargement of the axillary, cervical, or supraclavicular lymph nodes remains the most common complication of BCG vaccination¹⁰.

Cartridge-based nucleic acid amplification test (CBNAAT) was positive in our patient, and the results align with the findings of Mandal et al., where two cases were positive in the CBNAAT and had no other signs of TB as in the present study⁷. In the present study, we used GeneXpert MTB/RIF (Cepheid) test, which detects MTB complex (including MTB and BCG) and its resistance to rifampicin¹¹. This should be kept in mind in cases of post-BCG vaccination lymphadenitis, when a GeneXpert test is performed on the lymph node sample and a positive result is obtained.

The study by Singh¹⁰ suggested a higher incidence of nonsuppurative lymphadenitis after BCG vaccination than the suppurative type, and it is often self-limiting and resolves over a period. This condition is often subclinical and is often unnoticed. In this patient, although complications did not arise, the lymph node was excised at the request of the parents. A study conducted in Saudi Arabia¹² showed that the most effective treatment for lymph node enlargement caused by BCG injection was medical treatment in addition to needle aspiration, which was not in accordance with our current case where surgical intervention was performed, as per the parents' request.

To our knowledge and review of the available literature, we did not find cases with clinical manifestations similar to this case that were eventually diagnosed as conditions other than BCG adenitis (e.g., active tuberculosis).

This case report is presented to emphasize that BCG adenitis can occur even after the age of 1 year, and careful clinical history and appropriate investigations, along with the know-ledge that GeneXpert MTB detects MTB complex will aid in the correct diagnosis. Therefore, BCG adenitis can persist beyond the typically expected time, and monitoring the child until around 18 months of age is recommended without specific interventions. We also recommend observing the child until around 2 years of age before initiating specific interventions.