Borderline lepromatous leprosy is a form of leprosy that is characterized by an intermittent course between long periods of inactivity and bursts of activity caused by the progressive destruction of the skin leprosy elements.
Histologically, a borderline infiltration of inflammatory cells is determined both in the area of the hair follicles and beyond. The borders of the hair follicles become coarser and subsequently atrophy in some lesions. The skin turns red, skin erythema, scales, and cracks appear. Skin papules often leave behind daughter elements.
Rarely, a more severe form of borderline lepromatosis can develop, when lumpy superficial nodules transform into deep ulcers that leave scars on the skin, and are themselves gradually replaced by connective tissue stroma. As the disease progresses, the formation of syphilitic tubercles or sclerodes is possible. Exudate with a slight admixture of mucus is released from the resulting ulcers. Individual tubercles often ulcerate, with their tissue disintegrating, leaving depressions in the skin. The affected skin becomes rough and superficial scars form.