Case Number : Case 2162 - 21 September 2018 Posted By: Dr. Richard Carr

Although the upper dermal edema favours PMLE,  the epidermal atrophy,  subtle hydropic degeneration of basal cells and a fuzzy dermo-epidermal junction favour LE.  Stain for mucin and clinical picture will settle the issue. 

Agree with above.  DIF and ancillary studies may help, depending upon clinical correlation.

PLE, there are no necrotic keratinocytes , so I will go for PLE 

Neutrophils at the interface are more in keeping with acute LE.  But this is a difficult case. 

10 minutes ago, vincenzo said:

And there is some vacuolar degeneration  

But without any dermal mucin and with this impressive edema in papillary dermis PLE maybe is a better option...Waiting for the final diagnosis. 

There is reasonable number of neutrophils in the infiltrate including at DEJ. I would consider Non-bullous Neutrophilic LE in DDx (other names may include Sweet Syndrome like eruption in the context of SLE and Neutrophilic Urticarial Dermatosis, they all share many histological features).Clinical correlation is essential here to differentiate from PLE.

Thanks. I think I bowled a straight delivery again. Case came from a very experienced dermatologist. I thought it showed text-book features for polymorphous light eruption and did not do any special stains. Not sure I'm seeing a true interface pattern, dermal mucin or dermal neutrophils. 

I think Spot Diagnosis is a bit artificial especially as you're expecting something with a catch but occasionally there is no catch. In exams this can be a real issue as you want to know sometimes the candidate can deal with a straight forward bench case without equivocation. I did find that I had very few cases in my slide collection so for me at least my diagnosis is mainly based on "text-book" knowledge not personal experience.