Case Number : Case 1347 - 21 August Posted By: Guest

Fixed Drug Reaction (in the appropriate clinical setting i.e. rash recurring at the same site).
Less likely alternative would be Adult onset Still's disease due to prominent high dyskeratotic keratinocytes. Needs clinical correlation

The interface nature of the histopathology with necrotic KCs high in the epidermis, and the melanophages together with the recurrent nature of the rash makes me put fixed drug reaction first as Arti suggested, followed by EM (due to recurrent exposure to the same causative drug or recurrent attacks of herpes simplex).. Adult Still's is a nice suggestion but would have expected neutrophils in the infiltrate. Due to the lack of parakeratosis, I would less likely think of pityriasis lichenoides or lichenoid drug reaction... The case definitely needs good clinical correlation and if the only available data is a recurrent rash, then this will be a difficult situation... The word rash is a very non-specific word !!!!!! I would not expect it from a well trained dermatologist :-))

In an active lesion of fixed drug eruption I would expect some neutrophils and eosinophils and a deeper and more dense inflammatory infiltrate. Deeper melanophages would be expected if the lesion has recurred at the same site. In the absence of these findings I prefer erythema multiforme.

Yes well done Arti this is a case of fixed drug reaction (FDR). The actual history was "Recurrent rash in same places" but I felt that would make it too easy for all of you so I deliberately with held that information. You were all on the right lines though as this is a fixed drug eruption. I am guessing the patient is not very pigmented but even so there is a moderate degree of pigment incontinence that would definitely push one away from erythema multiforme (EM) or PLEVA. Eosinophils and neutrophils are certainly not a pre-requisite. High necrotic keratinocytes are a good clue to drug reactions in general including FDR. Weedon states that a heavier and deeper infiltrate in the dermis may also be seen compared with (EM).

Apologies for delay in posting 1337 and 1342 answers, I was on hols, but I hope you enjoyed the suspense!