One of the difficult areas in dermatopathology is the diagnosis of hypopigmented MF (HMF). Most of the cases affect children and young aged individuals. Constellation of clinical, histopathological and gene re-arrangement studies are needed to reach a definite diagnosis. In areas of the world like Egypt where resources are limited, TCR gene rearrangement studies are a luxurious kind of investigation that is not available on routine basis. Besides, it is known that TCR in HMF might be unreliable with many cases showing polyclonal pattern. This makes the histopathological features a cornerstone in the diagnosis.

I would like to thank Dr Carr for providing us, in his comment on one of his Friday cases, with a link to a very important article about hypopigmented interface T cell dyscrasia* which mimics HMF clinically but shows some histopathological differences from it. In the reported series, the hypopigmented lesions were mainly asymmetrical and the pathology was defined by a cell poor interface lymphocytes with mild cerebriform atypia. The interface lymphocytes were focal in nature and not involving the whole front of the epidermis. In some cases, the mildly atypical lymphocytes formed collections similar to Pautrier's abscesses but differed from those in HMF by the low grade atypia of the lymphocytes and by the usual association with degenerated melanocytes or keratinocytes. Also wiry fibroplasia was not detected in these cases. The cells expressed a significant reduction in CD7 and CD62L and in half of the cases; the cells were CD8 positive as in HMF. Clonality studies were negative. One case in the described series progressed to frank HMF. It is considered to be a distinct type of T cell dyscrasia that may only rarely progress to HMF.

This entity provided a perfect diagnosis to many cases that we see in Egypt, mainly affecting young age groups, with lesions clinically suspected to be HMF with affection of buttocks and thighs and with tinges of erythema and/or scaling, and pathologically showing features suggestive of HMF but very mild and focal in nature. We tended to be more on the safe side and used to call these cases early HMF and recommended phototherapy. I prefer now to call them hypopigmented interface T cell dyscrasia. It is treated by the same measures as HMF.

I would love to read your experiences with this entity.[list]
[*]Hypopigmented interface T-cell dyscrasia: A form of cutaneous T-cell dyscrasia distinct from hypopigmented mycosis fungoides

Magro et al., 2014, J Dermatology; 41: 609–617
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