Case Number : Case 1918 - 05 Oct - Dr Richard Carr Posted By: Guest

Epidermotropism with lymphocytes in epidermis larger than those in the dermis; thin wiry collagen fibres in papillary dermis point towards MF

Granular parakeratosis. And a clear cell pagetoid  diskeratosis as incidental finding. 

Oh, the newbie (to borrow Dr Carr's term) in me thought that they are haloed lymphocytes!

I think the clear cells are artefactual. To me, there is prominent SG yes but no PK to say granular PK. I think some structures are seen in the SC, would love to see Gram, PAS stains if available as I am thinking this could be erythrasma.

Agree with the comments made by Mona. Not granular PK.

Erythrasma was my first thought

Clinically, erythrasma does not look like psoriasis or contact dermatitis because it's flattish and has a typical colour. It's easily diagnosed by examining it with Wood's lamp and responds readily to antibiotics. There is hardly any need to biopsy the lesion. Yes, it could be dermatophytosis rather than erythrasma.

Thanks for all the comments. This is erythrasma with rather spectacular and in areas quite confluent artefactual perinuclear clearing of the keratinocytes. In so-called pagetoid dyskeratosis, (which is not dyskeratotic) a similar phenomenon (of perinuclear vacuolisation) usually occurs in focal cells scattered in the keratinocytes in the upper layers and is often seen in ano-genital, groin & axilla, skin tags in particular, as an incidental phenomenon. The cells in the latter situation also appear larger than the surrounding keratinocytes with cytoplasmic pallor/bubbly  appearances so it does looks somewhat different to the artefact we are seeing here but may be this is a variation on that phenomenon. Agreed a competent clinician won't  biopsy a clear cut clinical case of erythrasma - it is rarely the suggested diagnosis when we occasionally see cases. Often erythrasma is seen as an incidental finding.

Hopefully Philip Shapiro will supply us with Gram or PAS in due course.