Leprosy is a long-term spectrum disease and can present various clinical and
histopathological aspects. Between the two poles of leprosy, there is a wide range of
types, consisting of intermediate or borderline forms. In this chapter, the clinical,
histopathological, and bacilloscopic characteristics of the intermediate forms
(borderline-tuberculoid [BT], borderline-borderline [BB], and borderline lepromatous
[BL]) are presented and discussed. The main clinical and pathological characteristics
that allow the diagnosis and classification of leprosy among the different borderline
forms are described and illustrated in panel form, as well as their most significant
clinical and histopathological differential diagnoses are also discussed. The clinicalpathological classification of this disease has important implications in the choice of
the correct treatment, the understanding of the pathophysiology, and the development
of the reaction phenomena typical of leprosy.
Keywords: Borderline lepromatous, Borderline tuberculoid, Hansen’s disease,
Leprosy, Mid-borderline.
