Role of histopathology and HLA-DR expression in predicting lepra reactions: A retrospective analysis

Objectives To assess the role of histopathology and HLA-DR expression in skin lesions of leprosy in predicting lepra reactions. Methods Archived skin biopsy specimens from January to December, 2019, showing leprosy granulomas (at the time of diagnosis) were studied for features of lepra reaction and HLA-DR expression. Information on subsequent clinical manifestations of lepra reaction were collected from case records. Results We studied the archived skin biopsy specimens from 27 patients. Twelve patients (12/27, 44%) had clinically evident Type 1 lepra reaction (T1R) at diagnosis. Six patients who had no clinically evident lepra reaction at diagnosis manifested clinical features of T1R (5 patients) or T2R (1 patient) within 3 months of starting multidrug therapy (MDT). Four of the five (80%) patients who developed T1R and the lone patient who developed T2R after initiating treatment had histological features of the respective reactions in the biopsy specimen at diagnosis. All five patients who later developed T1R showed a moderate-to-strong expression of HLA-DR along the basal layer of the epidermis; a weak HLA-DR expression was noted along the epidermal basal layer of the lesional specimen of the patient who subsequently developed T2R. Conclusion A combination of histopathology and immunohistochemical analysis of HLA-DR expression in lesional specimens at the time of diagnosis of leprosy may help to identify patients at risk for T1R while on MDT. We need further studies to gather information on whether the added benefit of immunohistochemistry to predict patients at risk of lepra reaction is limited to T1R alone.