Leprosy is a chronic infectious disease whose etiological agent is
Mycobacterium leprae. Recently, Mycobacterium lepromatosis is also implicated as a
causative agent and has been identified in different forms of the disease. Leprosy is a
complex disease from a clinical, histopathological, and molecular point of view. The
wide diversity of clinical presentation and histopathological characteristics observed
throughout the disease spectrum and reactions render it a challenging disease in clinical
and pathological practice. This chapter discusses the main aspects of the disease and its
histopathological classification. An important approach to the bacilloscopic
examination, which is fundamental for the histopathological classification of the
disease, showing its quantitative and qualitative aspects, is discussed. The various
photographic panels demonstrate the bacillus' ability to parasitize different types of
tissues and cells of the skin and other organs of the human body. Multiple serial
histological sections stained using different techniques allow the main points addressed
in the text to be better understood through histopathological images. The entire content
of this initial chapter (Chapter 1) will be the basis for understanding the other chapters.
In the subsequent chapters, the clinical, histopathological, and bacilloscopic features of
leprosy forms (Chapters 2, 3, and 4), the reactional phenomena (T1R - Chapter 5 and
T2R - Chapter 6), the regressive changes observed in leprosy lesions during and after
treatment or relapse (Chapter 7), and some variants with special clinical characteristics
(Chapter 8) are discussed.
Keywords: Bacilloscopy, Hansen´s disease, Histopathology, Leprosy, Mycobacterium leprae, Mycobacterium lepromatosis, Ridley and Jopling.
