Case Number : Case 1884 - 17 Aug - Dr Arti Bakshi Posted By: Guest

Lichenoid reaction pattern with a striking hair follicles involvement. Lichen striatus is most likely given the clinical context described. 

TNF-blockers are well known to induce lichenoid drug eruptions however,  linear arrangement of such eruption including along the lines of Blaschko's must be exceptional if one dare to raise the possibility of Adalimumab induced lichen striatus. Drugs can trigger almost any dermatosis/tissue reactions.

Another possibility, besides adalimumab-induced eruption is linear lichen planus.

Dear All 

The immuno has now been uploaded on Dr Hafeez's case - 

DermpathPRO Admin

The compromise of adnexa is striking in this case and it always raises multiple possibilities in our DD when combined with a lichenoid infiltrate (lupus, lichen striatus, GVH, some infections, etc). I have seen this pattern before with immunecheckpoint inhibitors also (anti-PD-1 /CTLA-4) and did not know that anti-TNF alpha could also induce it. Blaschitis/lichen striatus Have  been reported in past secondary to this medication so agree with our colleague's dx

lichen planus.

http://www.derm-sinica.com/article/S1027-8117(14)00048-2/fulltext

adalimumab induced lichen striatus

Ok... this could of course be an adalimumab induced likenoid drug eruption...but the histology is that one of lichen planus, so my spot diagnosis is: Lichen Planus. 

Considering the clinical history of a linear eruption extending along one arm and the microscopic features of a lichenoid dermatitis with appendageal involvement, I favor lichen striatus.

Thanks Raul and Mona for providing the link to those published cases. I have came across 2 case reports of Etanercept associated lichen striatus as well from your references. The difficulty is one can not exclude co-incidental occurrence of this dermatosis especially when positive rechallenge with the claimed culprit is lacking in most of these cases.

Linear LP is very appropriate differential and still possible, it was the degree of adnexal involvement made me suggest L striatus over LP if one consider the latter as one of the histologic discriminators.

It would be interesting to know if Arti noted a perieccrine lymphocytic infiltrate in this case?

Great discussion! This is lichen striatus. That was the favoured clinical diagnosis and the periadnexal infiltrate was supportive. There was no perieccrine infiltrate in the bx.

Saman's comments are spot on regarding the problem of distinguishing coexistent (idiopathic) lichen striatus from drug induced lichen striatus. The patient has been on adalilumab for sometime and the rash is only recent. The drug has not been stopped so virtually impossible to say if the lichen striatus is drug induced or not!