Diagnosis of leprosy

Leprosy Mailing List, August 1st, 2008

Ref.: Diagnosis of leprosy
From: Das P. K., Amsterdam, The Netherlands


Dear Salvatore,

I refer to Dr. Khalid’s message: “Mnemonics in leprosy”, LML, June 15th, 2008. I am not sure what he really means with “Mnemonics in leprosy” but, I thank him for introducing the important subject of diagnosis of leprosy and its cardinal signs. I wish to add a few comments.

Together with the first Cardinal Signs of Leprosy (better defined by loss of sensation and hypopigmentation), it is also useful to mention "hypopigmentation and depigmentation". Complete loss of pigment (depigmentation) is not common in leprosy. Depigmentation is seen in vitiligo and, in my experience in India the depigmented patches of vitiligo are sometimes mistaken for leprosy.
In cases of tuberculoid (TT) leprosy and often in of borderline tuberculoid (BT) leprosy, identification of M. leprae by slit-skin smear examination is negative, therefore, the pathology of the biopsy at the margin of the active lesion is an important diagnostic tool.

Also, if possible, simple immunohistology is helpful. Immunohistology is performed using monoclonal antibodies to M. leprae PGL-1 and Lam (Ref.1). Positivity (even minor) will indicate TT leprosy.

Further, where possible, antibody titre to gel purified mycobacterial (not necessarily, M. leprae) 65KD antigen, using 1/400 diluted sera should be carried out and reading of OD value >.50 and can confirm the diagnosis of TT leprosy too (Ref. 2-4).

Hope this information is useful to you.

P. K. Das

Ref. 1. Amer.J.Pathol.(1999), vol . 154, p 1793-18040
Ref. 2. j.clin microbial(1990):`vol 28; p 379-382;
Ref. 3. Acta Leprologica (1989) vol 7(suppl.1)p 117-120;
Ref. 4. USA Patent No: US6,416,962 B1 Jul9,2002.