A Rare Case of Cutaneous Tuberculosis in the Dermatology Venereology Department of the Aristide Le Dantec Hospital, Dakar, Senegal

Introduction: Cutaneous tuberculosis (TB) is an infectious disease of the skin caused by Mycobacterium tuberculosis, also known as Koch’s bacillus (BK). Cutaneous TB is rare in developed countries but is steadily increasing in tropical African countries. We report a case of cutaneous tuberculosis in a patient who had been in close contact with a person with tuberculosis 20 years earlier. Observation: This was a 34-year-old patient with no significant past medical history who presented to the dermatology department in 2023. He reported having lived in close contact more than 20 years earlier with a relative who had died of pulmonary tuberculosis. In 2023, a keratotic papule developed on the outer aspect of his right arm, prompting a pharmacist to prescribe a topical corticosteroid. Two months later, this led to the development of a painless, scaly, crusted ulcerative lesion surrounded by a hypopigmented halo. The general physical examination revealed no signs of tuberculosis infection or weight loss. Examinations of the lungs, lymph nodes, gastrointestinal tract, bones, musculoskeletal system, and nervous system were unremarkable. A chest X-ray, an X-ray of the right arm, and a sputum smear test were all unremarkable. A biopsy was performed; histopathological examination revealed a nodular tuberculoid granuloma with central foci of caseous necrosis, typical of cutaneous tuberculosis. A diagnosis of cutaneous tuberculosis in its verrucous form was established. The patient was placed on antituberculosis therapy. A marked regression of the lesions was observed after 15 days of treatment, leaving only a few crusted lesions. From the third to the sixth month, a favourable course without relapse was observed. Conclusion: Cutaneous TB is rare, and its clinical and histological diagnosis is challenging given the variety of clinical presentations. The tuberculin intradermal test (IDR-tuberculin) plays a role in the diagnosis of cutaneous TB and should be correlated with histological examination.