Itching in leprosy

Leprosy Mailing List, April 30^th, 2009

 

Ref.:   Itching in leprosy

From: Narasimha Rao P., Hyderabad , India

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Dear Salvatore,

 

This mail is in regard to on going discussion  on itching in leprosy.  Itching is a not a known symptom of leprosy.  However, many itchy conditions can occur as co-dermatosis in leprosy patients.

 

When leprosy patients are seen in dermatology out patient clinics of developing country like India , it is generally observed that these patients are prone in equal measure to all the dermatological disorders as other patients of their social/peer group.  Hence the occurrence of common dermatological conditions like scabies, dermatophytosis (tinea infection), contact dermatitis, skin eczemas, papular skin reactions to insect bites etc. is quite common in leprosy patients.  All these dermatosis mentioned are itchy conditions and can easily be identified by trained skin specialist.  However, when they occur in a leprosy patient they can be confusing clinically even to a trained eye, as their classical features are modified depending on the extent and type of leprosy.  It is commonly observed that all these itchy conditions when associated with leprosy become /present as less itchy conditions. 

 

Below mentioned are few commonly associated dermatological itchy conditions modified in leprosy.

 

Asteatotic leg eczema:  More commonly seen bilaterally in BL or LL patients, more so after treatment with Clofazimine which adds to xerosis of skin. This type eczemas continue to occur many years after patient is made RFT.  Occasionally unilateral leg eczemas are seen in area of anaesthetic/ hypoaesthetic skin lesions of BT  patients.  In these type of eczema, although scaling is profuse, often accompanied by fissuring and secondary infection, itching as a symptom is usually very mild or not reported at all in a patient of leprosy, compared to a non-leprosy patients with similar involvement. 

 

Papular urticaria:  Papular skin reaction to insect bites commonly observed in tropics is observed to be less symptomatic in BL-LL leprosy patients. Itching is a not a prominent complaint in these patients compared to non leprosy patients with this condition. 

 

Scabies:  Wide spread crusted type of scabies, also  known as ‘Norwegian scabies, which is known to occur in mentally challenged, paraplegics, immuno-supressed etc, is also reported in leprosy.  Vijaikumar M, Thappa DM. Crusted (Norwegian) scabies in leprosy. Indian J Lepr..2001 Jan-Mar;73(1):55-8.  Itching which is the principal feature of scabies is absent in this condition.

 

Tinea corporis:  When tinea corporis lesions co-occur in leprosy patients with type I reactions, they could mimic the patches of type 1 reaction, especially regressing phase of patches when they scale off.  However, differentiating feature is the tinea corporis patches are itchy and when in doubt scraping for fungal filaments on KOH mount would help in the diagnosis.  I have few photographs of this co- infection and would  be happy to forward to those interested to have them.  The case of patient presenting with itching on buttock turning out to be  type 1 reaction on histopathology, (ref: letter from Nunzi E, Italy, Leprosy Mailing List, dated, April 28th, 2009; Itching as presenting symptom of reversal reaction),could be one such instance, as buttock is a common site for tinea infection and it could be a co-infection in this patient.

In summary, it can be stated that itchy dermatological conditions when associated with leprosy patient can be  a) masked (incognito)  b) less inflamed and show modified tissue reaction, c) less itchy,  or d) have normal clinical features.  Hence it is important to consider/rule out associated dermatological conditions as a cause of itching in these patients. Unfortunately , however, it is often  difficult to rule out even common skin conditions such as papular urticaria, insect bite reactions, early scabies etc. by laboratory tests.

 

In my opinion, when patient of leprosy complains of itching, careful search should be made for (missed) underlying dermatological condition.  The associated conditions could vary depending on the geographical area/ economic/ social status of the patient.  This is necessary because itching is not a known feature of leprosy and there is no accepted scientific or pathological basis for it to be present in either during normal course or during reactions of leprosy.

 

With best regards,

 

P. Narasimha Rao