Mycobacterium leprae (aka: Leprosy, Lepromatous Leprosy)

General:

Gross:

Microscopic: In lymph nodes, there is a progressive accumulation of large, pale, rounded histiocytes (known as "lepra" or "Virchow" cells) which can expand the sinuses to massive proportions.

Staining:

• Positive: Wade-Fite+, Fite-Faraco+, Fite+. These show packing of the pale histiocytes with acid fast organisms.
• Negative: Typically Ziehl-Neelsen- as the decolorizing step is too harsh for M. leprae.
• Suggested panel:

(1)

Images:

Note the "cleared out" histiocytes which are actually packed with acid-fast bacilli (not visible on this stain).

Cases: