Unexpected Deltoid Abscess from BCG Vaccination in a Healthy Adult: A Case Report

Introduction

The attenuated Bacillus Calmette-Guérin (BCG) vaccine is administered to prevent tuberculosis worldwide mainly for the pediatric population [1]. It was first created by Albert Calmette and Camille Guérin over a century ago, and the first human being was given the BCG vaccine in 1921 [1]. The vaccine contains a live, attenuated form of the bacteria, Mycobacterium bovis, which is part of a genetically similar group of bacteria called the Mycobacterium tuberculosis complex [2]. The most common routes of administration are intradermal and intra-cutaneous [1]. The BCG vaccine also protects against other nontuberculous mycobacterial infections, such as leprosy and Buruli ulcer [1].

Complications of BCG vaccinations are rare and generally non-severe. The most common complications include lymphadenopathy, ulceration of the inoculation site, residual scarring, and keloid formation [3]. Studies have shown that 0.001% of intradermal BCG vaccinations resulted in local complications in immunocompetent patients [3]. Factors such as the incorrect route of administration and an immunocompromised patient can increase the risk of complications from the BCG vaccine [4]. Rare complications of the BCG vaccine have been reported, primarily in the pediatric population, such as inoculation-site abscess [5,6], lymphadenitis, BCG osteomyelitis, and disseminated infection in the setting of an immunocompromised patient [3]. We present an unusual case of a deltoid abscess following intramuscular administration of the BCG vaccine in an immunocompetent woman.

Case Report

A 30-year-old woman with no past medical history was recommended to receive the MMR vaccine in an outpatient clinic. She mistakenly received the BCG vaccine intramuscularly in her left deltoid, and this error went unnoticed. The BCG vaccine she received was a freeze-dried variant that contained the live, attenuated Mycobacterium bovis dissolved in 0.1 mL of normal saline. One week later, she started to developed pain, swelling, and redness at the injection site on her shoulder. The patient denied any fever, recent trauma, or drainage from the shoulder. On physical examination, there was an area of erythema, induration, and tenderness on her left deltoid muscle. There was no obvious discharge. Laboratory investigations showed normal WBC count (5.0×109/L) with normal differential; her CRP was normal as well (4 mg/L). Following this, she was suspected to have cellulitis and was given a 7-day course of oral cefuroxime. However, there was no improvement in her condition.

Two weeks after the BCG vaccine injection, a T2-weighted magnetic resonance imaging (MRI) scan was done on her shoulder, which showed an intra-deltoid pseudo-lesion with a high signal indicating edema and no definitive wall or fluid collection (Figure 1). An ultrasound scan done 2 weeks later suggested a thick-walled fluid collection with an estimated volume of 15 mL in the lateral aspect of the soft tissue of the upper arm, consistent with an abscess (Figure 2). To identify the pathogen responsible, she underwent fine-needle aspiration (FNA) of the lesion. A bacterial culture and an acid-fast bacilli (AFB) smear were done on the aspirated fluid, yet both tests returned negative. Yellow, purulent discharge began to drain from the left shoulder area 2 days following the FNA. This discharge was used for an AFB smear and culture with sensitivities. The auramine-rhodamine stain revealed yellow fluorescent bacteria, consistent with Mycobacteria (Figure 3). The liquid culture also returned positive for pan-sensitive Mycobacterium tuberculosis complex (Figure 4), confirming the diagnosis of a Mycobacterium tuberculosis complex deltoid abscess. Genome sequencing tests to differentiate between the species of Mycobacterium tuberculosis complex in the discharge sample were not completed due to a lack of resources to facilitate these tests. A chest X-ray was ordered to rule out possible pulmonary tuberculosis, and the results did not uncover any active or previous TB lesions (Figure 5).

Two months following the initial BCG vaccine injection, first-line anti-tuberculosis medication – rifampicin (600 mg daily), isoniazid (300 mg daily), pyrazinamide (1500 mg daily), and ethambutol (1200 mg daily) – was started. The initial treatment was effective, and she recovered fully and reported no further symptoms 6 months after initiation of the anti-tuberculosis treatment. Another MRI scan was done during a follow-up 3 months after completion of anti-tuberculosis treatment, revealing a significant decrease in size of the BCG deltoid abscess (Figure 6).

Discussion

The BCG vaccine, when given intradermally to appropriate patients, is generally safe, with a low risk of complications [4]. These adverse events are usually self-limiting and restricted to the injection site [4]. Administration of the BCG vaccine intramuscularly is commonly the result of an error and can lead to rare and preventable complications, even in immunocompetent patients. On the other hand, the measles, mumps, and rubella (MMR) vaccine is normally given intramuscularly to patients. A reasonable explanation for the error in this case is that the healthcare professional administering the vaccine confused the BCG vaccine for the MMR vaccine and injected it intramuscularly. Furthermore, this case demonstrates a complication of erroneous intramuscular administration of the BCG vaccine; only a few cases of this type of incident have been recorded in the literature [4–6].

Erythema and swelling of the shoulder is a symptom of various infectious and non-infectious differential diagnoses, such as a hematoma, bursitis, or cellulitis. It can be difficult to diagnose rare conditions, especially when a much more common diagnosis presents similarly. Our patient was initially suspected to have cellulitis on her shoulder, but the diagnosis was revised after a treatment course of cefuroxime proved to be ineffective. Development of suppurative adenitis, inoculation-site abscess, type IV granulomatous hypersensitivity reaction, secondary bacterial infections, and intramuscular abscess secondary to BCG vaccination have been reported in the pediatric population [5–8], most commonly in immunocompromised patients. In our patient, an abscess secondary to the BCG vaccine would at first appear to be a very unlikely diagnosis considering that the patient was a healthy immunocompetent adult, in contrast to the cases in the literature.

Although the diagnosis of an abscess secondary to the recent BCG vaccination could have been made on clinical grounds, microbiology laboratory tests can be extremely useful; the diagnosis of an intramuscular abscess due to a BCG vaccine was confirmed in this case only after cultures using abscess discharge returned positive for a Mycobacterium tuberculosis complex along with sensitivities. The most probable source of the Mycobacterium tuberculosis complex deltoid abscess was the intramuscular injection of the BCG vaccine, since Mycobacterium bovis, the live attenuated bacteria present in the BCG vaccine, is one of the species associated with the Mycobacterium tuberculosis complex. Because the cultures showed sensitivity to first-line anti-tuberculosis medications, treatment with antibiotics were started and resulted in resolution of symptoms after a 6-month course, and an MRI scan performed 3 months after treatment showed a significant decrease in the size of the deltoid abscess. Proper training in vaccine injection technique is a key factor in prevention of BCG vaccination complications. Implementing measures to confirm the correct vaccine and mode of administration for the patient before vaccine injection would also prevent future errors, as occurred in this case.

Conclusions

Abscess formation following a BCG vaccination is a rare complication, yet certain factors, such as an immunocompromised status and incorrect vaccine administration technique, increase the risk of BCG vaccine complications. Although there is no consensus on the optimal management of an abscess secondary to a BCG vaccine, anti-tuberculosis antibiotics appear to have played a significant role in the treatment of this patient. Strategies to prevent complications from the BCG vaccine include adequate training in vaccine administration and medication identification skills.