Fw: (LML) Co-occurrence of type 1 and type 2 leprosy reactions

 

Leprosy Mailing List –  December 15,  2025

 

Ref.:  (LML) Co-occurrence of type 1 and type 2 leprosy reactions

From: Joseph Chukwu, Enugu, Nigeria

 

 

Dear Pieter,

Thank you very much for the excellent work you and your team continue to do in moderating this forum.

Permit me to contribute to the subject of co-occurrence of type 1 and type 2 leprosy reactions, raised by our esteemed veteran colleague Ben Naafs.

My colleagues and I consulted widely and came up with the underlisted (possible) explanations.

It would interest us to know what you (or indeed any other LML readers) think about them.

 

While the mechanisms behind type 1 and type 2 leprosy reactions are distinct, there is some overlap in the immune processes that may explain the co-occurrence.

1. Immune system fluctuations: Leprosy reactions are immune-mediated responses. The patient's immune system can fluctuate between different states, leading to both a Th1-dominant response (associated with Type 1 reactions) and a Th2-dominant response (associated with Type 2 reactions) occurring simultaneously or sequentially. These immune responses are not always mutually exclusive, and the body can react to M. leprae in multiple ways at once.
2. Disease progression or transition: A patient may have borderline or mixed forms of leprosy, where the disease presents with features of both tuberculoid and lepromatous leprosy. This can make the patient susceptible to both types of reactions. For example, a patient might experience a Type 1 reaction as the immune system tries to control the infection (reversing from lepromatous to tuberculoid), while at the same time, a Type 2 reaction could occur due to immune dysregulation or as part of the inflammatory response.
3. Treatment and immune system response: The introduction of treatment (such as multidrug therapy or steroids) may trigger immune responses that lead to reactions. If a patient is receiving therapy for leprosy, the shift in immune balance might trigger both types of reactions simultaneously, particularly if the body is transitioning between different forms of the disease.

4.    Nerve damage and immune system activation: In some cases, nerve damage caused by the Type 1 reaction (reversal) could stimulate an immune cascade that also promotes the onset of Type 2 reactions (ENL). Inflammation in the nerves can create an environment where both immune mechanisms are activated simultaneously.

 

 

Best regards,

 

Joseph Chukwu

Enugu, Nigeria

________________________________________________________________________________

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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