What is in paucibacillary (PB) leprosy?

Leprosy Mailing List – November 9th, 2011 

Ref.:   What is in paucibacillary (PB) leprosy?

From: B Naafs and P A M Schreuder, The Netherlands

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Dear Salvatore,

We thank Dr. Jaison for his message “What is paucibacillary (PB) leprosy?” (LML Oct. 15^th, 2011).  We just want to make a few observations to add to the discussion.

1. Dr. Leiker recognised that there existed a classification between tuberculoid (TT) and borderline tuberculoid (BT) leprosy.  He called that LRT = Low Resistant Tuberculoid.  It presents one or a few lesions (not symmetrically distributed) with a few satellites.  Skin smears are mostly negative.  It was a group of patients who hardly had problems or went into reaction.  It is a pity this was never taken up by the international leprosy community.

2. In the old times BT with a max. smear bacteriological index (BI) of 1+ were indeed treated as PB.  It later on turned out that especially BT with multiple lesions relapsed.  In those cases were nerve biopsies were taken, many of those had a positive RC nerve biopsy (Dr. Ben Naafs).  To reduce the PB relapse rate to a lower level a new clinical classification system was put in place: those patients with less than 6 lesions or with not more than 1 nerve involved were called PB.  That indeed had the intended result.

3. Indeed, when smears would be taken in PB patients, 2 - 4% will be positive (ref. 1).  Sometimes even a single lesion turns out to be positive.  In case of  nerve biopsies in PB patients even more will be  positive.  Nevertheless, we do not find a relapse rate of 2 - 4% in PB patients, much less so.  Even in the old times, not all BT smear positives or with many lesions relapsed.

4. The first result of the Uniform MDT schedule shows  that the PB relapse rate has become even lower than the MB relapse rate.  Which could have been expected.

5. We are aware of Opromolla’s hypothesis, but which is not shared by many.  In Thailand we saw and treated (with steroids) successfully many patients with a late reaction.  The big majority of these patients improved and never relapsed (Dr. Pieter Schreuder).

May we also refer to the article by Maria Angela Bianconcini Trindade et al (reference 2): The histopathological changes in 167 biopsies from 66 leprosy patients were studied.  The patients were selected when their sequential biopsies demonstrated either different patterns or maintained the same pattern of granulomatous reaction over more than two years during or after the treatment of leprosy.  In 57 of the patients studied, a reactivation was seen which coincided with a decrease in the BI, suggesting that this reactivation (reversal reaction or type 1 leprosy reaction) coincides with an effective capacity for bacteriological clearance.  In nine patients, an increase of the BI or persistence of solid bacilli occurred during the reactivation, indicating proliferative activity, suggestive of a relapse.  The histopathological aspects of the granulomas were similar in both groups.  CONCLUSION: bacteriology (slit-skin smear examination) provided the only means to differentiate a reversal reaction from a relapse in patients with granulomatous reactivation.  The type 1 leprosy reaction may be considered as a partly effective immune reconstitution (reversal, upgrading reaction) or as a mere hypersensitivity reaction (downgrading reaction) in a relapse.

Abraços,

Ben Naafs

Pieter AM Schreuder

References
1.Rao PS, Ekambaram V, Reddy BN, Krishnamoorthy P, Kumar SK, Dutta A.Is bacteriological examination by skin smear necessary in all paucibacillary leprosy patients in mass control programmes? Lepr Rev. 1991;62:303-309
2.Trinade MA, Benard G, Ura S, Ghidella CC, AVelleira JC, Vianna FR, Marques AB, Naafs B, Fleury RN. “Granulomatous reactivation during the course of a leprosy infection: reaction or relapse. PLoS Negl Trop Dis. 2010 Dec 21;4(12):e921