Two subcutaneous cold abscesses after accidental bacillus Calmette–Guérin revaccination in an adult with urothelial carcinoma of the bladder

The complications of bacillus Calmette–Guérin (BCG) revaccination are poorly described. The objective was to report a rare case of two subcutaneous abscesses caused by accidental BCG revaccination. A 63-year-old patient, followed for non-invasive urothelial carcinoma of the urinary bladder resected on two occasions with a recurrence, was scheduled for BCG immunotherapy. One month before admission, the patient, accidentally, received two subcutaneous injections of BCG in the left arm and periumbilical area. Three weeks later, the patient presented two subcutaneous cold abscesses at both injection sites. Ziehl–Neelsen stain found an acid-alcohol resistant bacillus. A culture showed Mycobacterium bovis. The patient received local isoniazid for two months with good evolution. Although adverse reactions are rare after BCG revaccination, it is crucial to continue monitoring to learn more and choose timely treatment if they occur.