Brain abscess caused by Mycobacterium avium complex in an adolescent with an inborn error of immunity.

Mycobacterium avium complex (MAC) infections of the central nervous system are rare and represent a diagnostic challenge, especially in immunocompromised patients. Comprehensive management requires early diagnosis, prolonged antimicrobial treatment, and, in some cases, neurosurgical interventions. We present the case of a 16-year-old patient with an inborn error of immunity caused by a variant in the NFKB1A gene, who consulted for paresis of the left upper limb. A diagnosis of brain abscess was made using central nervous system (CNS) imaging, and the etiological agent was confirmed by neurosurgical biopsy culture after an unfavorable clinical course with initial empirical treatment. The patient was treated with rifampicin, ethambutol, levofloxacin, linezolid, clarithromycin, and high-dose dexamethasone, achieving significant clinical and radiological improvement after prolonged treatment.