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Porokeratosis: Is it a single 'disease'?

Sasi Attili


Many a time in life we take things for granted because that is what we have been taught to believe. The human mind is too bogged down by events in daily life that we do not ponder to question what is already believed to be 'known'.

Take the case of Porokeratosis. What is it?

Porokeratosis is defined by the presence of the pathognomonic coronoid lamella, a finding certainly not specific to porokeratosis, found in a number of other inflammatory and neoplastic conditions. So essentially the 'coronoid lamella' may be regarded as a tissue reaction pattern like 'lichenoid dermatitis' or a 'spongiform pustule'. Not all lichenoid dermatitidis are lichen planus and not all spongiform pustules are a manifestation of psoriasis.

Yes there are familial forms of porokeratosis which are proven to be genodermatosis, some inherited autosomal dominantly. But there are a number of other acquired forms, of unknown etiopathogenesis. However are these all really related enough for us to call them all variants of 'porokeratosis'? The only thing they have in common is a 'coronoid lamella', which is just a tissue reaction pattern!

Porokeratosis has been described to show various inflammatory changes, ranging from a superficial perivascular inflammatory infiltrate to a dense band like lichenoid infiltrate mimicking lichen planus. I recently had a case where a middle aged lady presented with pigmented plaques on the face which in the absence of a coronoid lamella (present clinically!) one would suspect either DLE or LP. Histopathological examination revealed a lichenoid dermatitis associated with a coronoid lamella. Do I now sign this out as LP with a coronoid lamella or accept the inflammatory changes to be part of porokeratosis (since someone has already described and labelled these changes to be part of the porokeratotic process) and call this porokeratosis?

Given that the 'coronoid lamella' is just a tissue reaction pattern I am more inclined to call this 'LP with a coronoid lamella'. I am well aware that others might defer. But would be interested in the counter argument.


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Robledo F. Rocha


In my opinion, cornoid lamella really is a tissue reaction pattern, but different from parakeratotic column. In its full expression, cornoid lamellae feature, besides a parakeratotic column resting on a shallow epidermal depression, absence of the underlining granular layer and presence of dyskeratotic keratinocytes in the spinous layer, findings indicative of a vertically-oriented clonal disordered keratinization with gradual centrifugal expansion, hence individual lesions present clinically as a horny ring around central atrophic skin and the inclined parakeratotic columns point away to the center of the lesion. Thus described, cornoid lamellae can be found only exceptionally in cutaneous diseases other than porokeratosis.

In contrast, parakeratotic columns without those specific underlining keratinocytic disturbances may be found in diseases like lichenoid keratosis, viral warts, ichthyosis, seborrheic keratosis, actinic keratosis/squamous cell carcinoma. In such situations, essential microscopic findings of these diseases are present as well.

However, whereas the shared clinicopathological characteristics of porokeratosis suggest it is a single entity, its variants are likely etiopathogenic unrelated and might represent different entities.
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Dear Dr. Robledo. Thanks for your views. I beg to differ as I have seen genuine coronoid lamellae in unrelated diseases and this has been described in all major text books too. The problem is that we do not really know how/ why a coronoid lamella is formed. All inflammatory skin diseases expand centrifugally as 'expansion' by definition cannot be centripetal. So that is not unique to PK.

It is quite possible that whatever mutative event induces the dyskeratosis and parakeratotic column in so called 'true' PK, may also be triggered by the inflammatory process itself in other inflammatory diseases, thus leading to the formation of a true coronoid lamella. I have my reservations against coronoid lamella being the primary event in this entity. I believe that this is simply an epiphenomenon that might be observed in various inflammatory diseases. If this is a true dyskeratotic disorder, one cannot explain the associated intense inflammation described.
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