Leprosy Mailing List – April 5, 2016
Ref.: (LML) The Diagnosis of Leprosy
From: Ben Naafs, Salvatore Noto, Pieter Schreuder
Dear LML readers,
In response to the ongoing discussion about the diagnosis and classification of leprosy on LML we would like to emphasis that the 3 major criteria for the diagnosis of leprosy are already known for over 100 years. They are:
1) Loss of sensation to touch in a skin lesion.
This criterion can be replaced by loss of sensation for heat and cold, positive histamine test, absence of sweat after heat or running, or a difference with normal skin after injection of pilocarpine. This is all in the hypo-pigmented or erythematous skin patch.
2) Enlarged peripheral nerves on palpation
It can be replaced by ultrasound determination of the size of the nerves or by nerve function loss. Trauma and hereditary motor or sensory neuropathy have to be excluded. Nerve conduction velocity studies may be of help.
3) Positive skin smear.
It can be replaced by skin or nerve biopsy with AFB's. Be sure that the destaining of the AFB's is for M.leprae and not for M.tuberculosis! This criterion can be also replaced by positive antiPGL1; and PCR or NASBA positive for M.leprae.
Two out of these three criteria confirm the diagnosis of leprosy. This does not mean that in the field an experienced health worker may not provisionally diagnose a patient on one criterion and start treatment. Because early treatment of leprosy prevents live long disability. It is a balance, this against the side effects of drugs and the stigma related to the diagnosis.
Early lepromatous, early borderline-lepromatous, early tuberculoid and indeterminate leprosy deserve special notes. Early lepromatous and early borderline-lepromatous often do not show loss of sensation in the skin lesion (or in the infiltrated skin) and may not have enlarged nerves or detectable nerve damage. Indeterminate leprosy does not show peripheral nerve involvement, and this can also be the case of early tuberculoid leprosy.
Finally, in the field, in endemic areas with no available laboratory facilities, the experienced leprosy worker has to rely on clinical skills only. That is: aspects of the lesions (borders, distribution, signs of inflammation; redness infiltration, etc.), detection of loss of sensation, neuritis, sequelae of nerve function loss and palpation of peripheral nerve trunks.
In cases of doubt, it is wise to re-examine the patient after 3 months; in general leprosy develops slowly.
Always consider the balance; side effects of treatment and stigma against damage to the patient by not treating.
With regards,
Ben Naafs, Salvatore Noto and Pieter Schreuder
LML - S Deepak, B Naafs, S Noto and P Schreuder
LML blog link: http://leprosymailinglist.blogspot.it/
Contact: Dr Pieter Schreuder << editorlml@gmail.com
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