Case Number : Case 2726 - 17 December 2020 Posted By: Saleem Taibjee

The low power architecture and history made me favour Jessner's lymphocytic infiltrate.  However, at higher power there are quite a few neutrophils in the infiltrate, possibly some mucin in the dermis, and maybe a hint of basement membrane thickening.  The overall pattern isn't really loose enough for "palisaded" neutrophilic granulomatous dermatitis.

I'm struggling to fit it precisely into a unifying diagnosis.  Certainly lupus comes into the equation.  I would also check syphilis serology, but that doesn't really fit with the history.

?Urticaria

perivascular and perieccrine lymphocytes, no interface change, some mucin is seen in dermis

I would go with tumid lupus

mentor says Common things being common, when you see a slight vertical orientation and interstitial neutrophils cut levels for folliculitis which can be itchy.

Very well done!

Yes, this is acute folliculitis.

This is a routine case just from last week. I have seen several examples over the years of folliculitis not evident in the initial levels. And as we can see, it can lead to all sorts of confusion, and understandable misinterpretation. When I saw the initial levels on this case, I was genuinely considering palisaded neutrophilic and granulomatous dermatitis. In a previous case, I have seen a close mimic of Sweet’s.

But common things are common, it is remembering to request levels. The clue is the clinical description of itchy spots. In such cases, the intervals need to be at narrow intervals (e.g. 25-50 microns) to avoid missing the follicle.

See images from the additional levels below.

Very educational case. Thanks Saleem. 

 wonderful case. Dr Tabjee,you are such a good story teller and wonderful teacher. Thanks