Leprosy with subsequent type 2 reaction masquerading as cutaneous tuberculosis: a case report and diagnostic pitfalls in a non-endemic area

Leprosy, a chronic infectious disease caused by <i>Mycobacterium leprae</i> complex, remains a significant global health concern despite being curable with multidrug therapy. Delayed diagnosis is common, particularly in non-endemic regions or when presenting with atypical symptoms. This can lead to missed opportunities for early intervention, potential disabilities, and increased transmission. Misdiagnosis is often compounded by leprosy's ability to mimic other conditions, as illustrated in this case report. We present a 43-year-old Filipino woman residing in Eastern Saudi Arabia, who presented to a dermatology clinic with a four-year history of recurrent skin rashes and a one-year history of painful, itchy nodules on her shins. She denied any systemic symptoms, recent travel, or known tuberculosis (TB) contact. Physical examination revealed multiple erythematous nodules on her shins with hyperpigmentation, but no lymphadenopathy or other skin lesions. Initial laboratory tests, including blood counts, liver and kidney function, inflammatory markers, and HIV screening, were normal. Chest X-ray was unremarkable. The patient's clinical presentation and laboratory results led to a provisional diagnosis of extrapulmonary TB, and she was started on anti-TB treatment. However, her condition did not improve after several months of treatment. A skin biopsy was performed, and histopathological examination revealed granulomatous inflammation with acid-fast bacilli, raising suspicion for leprosy. Subsequent culture of the skin biopsy unexpectedly yielded <i>Mycobacterium leprae</i>, confirming the diagnosis of lepromatous leprosy. The case study highlights the diagnostic challenges associated with leprosy, especially in non-endemic regions. The patient's atypical presentation, lack of systemic symptoms, and the unexpected growth of <i>M. leprae</i> in cell-free culture media contributed to the initial misdiagnosis and delayed treatment. Early suspicion, prompt skin biopsy, and appropriate culture techniques are crucial for accurate diagnosis and timely initiation of effective therapy to prevent disability and transmission. This case also underscores the importance of considering leprosy as a differential diagnosis in patients presenting with atypical skin lesions, even in non-endemic areas. Continued awareness and education among healthcare providers are essential to improve early recognition and management of this treatable disease.