Histological, immunohistochemical, and serological markers of lepra reactions in leprosy

Lepra reactions or ‘reactions’ in leprosy are immunological phenomena with distinct immunopathogenesis resulting in characteristic clinical manifestations and often are precursors of neuritis and disability. The reactions seen in leprosy are type 1, type 2, or erythema nodosum leprosum reaction and Lucio phenomenon. When undiagnosed or with a delay in intervention, these acute events affecting nerves and other organs can cause irreversible deformities and disabilities. Much research is ongoing to identify definitive biomarkers to predict and diagnose leprosy reactions early, to arrest the immunopathogenesis, prevent the morbidity/disabilities associated with reactions, and improve quality of life. After a brief introduction to leprosy and its reactions, we discuss the advances in identifying biomarkers for leprosy reactions. The serological, histopathological, and genetic markers have been covered in respect of all the three lepra reactions. We have strived to correlate the findings with respect to biomarkers for reactions with clinical features, pathogenesis, and immune histopathology of reactions for a better understanding.