Which WHO classification is most likely to develop a type II reaction (erythema nodosum leprosum)?

Erythema nodosum leprosum is a type II hypersensitivity reaction associated with leprosy, particularly in patients who have a higher bacterial load. In the context of the World Health Organization (WHO) classification of leprosy, multibacillary leprosy is characterized by the presence of a significant number of bacilli, leading to a more severe form of the disease.

Patients with multibacillary leprosy often experience a greater immune response due to the larger bacterial load, which increases the likelihood of developing immune-mediated complications such as erythema nodosum leprosum. This condition manifests as painful nodules on the skin and reflects an underlying immune response to the persistent mycobacterial antigens that are present in higher quantities in multibacillary cases.

In contrast, single lesion leprosy and paucibacillary leprosy are associated with a lower bacterial load and a less aggressive immune response, making the occurrence of type II reactions less likely. Non-infectious leprosy, while less common, does not align with the development of type II reactions in the same way as multibacillary cases do due to the absence of a significant bacillary presence. Therefore, the correct