Case Number : Case 2681 - 15 October 2020 Posted By: Saleem Taibjee

Pre-bullous phase of pemphigoid.

dermal edema with eosinophils

Pemphigoid should be excluded-

There is a subepidermal split at the edge of image 3 with subtle    “impending” separations foci in the centre of image 5.

This combined with the appearance of eruption and patient’s age is highly suggestive of pemphigoid, DIF results can complete the picture.

13 minutes ago, Saman Fatah said:

There is a subepidermal split at the edge of image 3 with subtle    “impending” separations foci in the centre of image 5.

This combined with the appearance of eruption and patient’s age is highly suggestive of pemphigoid, DIF results can complete the picture.

Totally agree with the above description. And I seem to see a cluster of jewels at the edge of the larger lesion, in last fig; or am I wrong?

Vincenzo: I believe you meant (crown of jewels) which is a descriptive term used mostly for the appearance and arrangement of blisters in Linear IgA Bullous Dermatosis (LABD) particularly the childhood variant. 
Sub-epidermal immunobullous disorders can have overlapping clinical/histological/immunopathological features and in my view that sign is not entirely specific for that particular disease and could occasionally be seen in other immunobullous diseases.

This is an example of ‘pre-bullous’ pemphigoid. The Direct immunofluorescence was confirmatory.

From a clinical point of view, fixed urticated plaques help to distinguish from simple urticaria (transient plaques). This pre-bullous phase can occur as a prodrome (to sudden eruption of blisters) for several weeks, and is characteristically very itchy. Sometimes, after careful clinical examination, occasional small blisters may be found as a clue to the correct diagnosis as hinted at in the clinical photos above.

As one would expect, histologically well-formed subepidermal blisters also tend to be lacking in this pre-bullous stage.

This case illustrates 2 histological clues:

In the 5th image, we can see tiny subepidermal blisters which I like to call ‘mini-blisters’. Also see below.

As Saman points out, in the 1st and 3rd images, we can see focal subepidermal clefting at the very edge of the biopsy. This can be referred to as the ‘micro-Nikolsky sign’, and was first introduced to me by Dieter Metze. Conceptually, the shearing force as the punch biopsy instrument is rotated into the skin creates a cleft at the very edge of the specimen. See below.

BW
Saleem

Thanks Saleem for explaining those 2 microscopic signs and the likely mechanism in the last image.

Thanks, Saleem!