General Remarks on the Disease.
From the above description and the cases related in support of it, what inference may be drawn as to the nature of the disease and its relation to other skin affections? Frankly, at present I am quite unable to even conjecture its pathology, or to suggest, with one exception, any relation to other dermatoses. In my first cases I supposed that it was an early stage of Mycosis fungoides, though the absence or trifling character of the subjective symptoms did not lend this any support. I clung to this theory, however, faute de mieux, for a long time, but it received its coup de grace when I met with a case of over thirty years’ duration without any such malign development.
At the Dermatological Society of London, where Mr. George Pernet and myself have shown three cases, among other suggestions, that of a possible seborrhoïde or Urticaria pigmentosa have been made. Against the former, the absence of scaliness in a large proportion of the patches, that the patches are in the skin, not raised above, and that itching is an exceptional feature, together with the unchanging character of the lesions, effectually bar the diagnosis of a seborrhoïde. Neither can I find anything beyond the yellowish tint frequently, but not always, present to support the idea of Urticaria pigmentosa. The absence of itching in nearly all the cases of Urticaria factitia, while the patches are level with the normal skin, and their unchanging character, are all strongly against such a diagnosis, to say nothing of the extreme rarity of adult Urticaria pigmentosa and the improbability of one man meeting with nine cases of it. The histology also negatives this.
I can therefore, at present, only regard it as a dermatosis sui-generis, of which the pathology must be left an open question, as Mr. George Pernet’s report on the histology of the portion of skin removed from Case 8 does not throw much light upon the pathology. There remains only the affection described by Brocq, to which, certainly, there are closer resemblances than to any other affection.
Brocq[[1]] divides the group which he calls parapsoriasis into three groups:
First variety (very closely related to psoriasis), Parapsoriasis guttata. Jadassohn’s case is probably to be referred to it.
Second variety (intermediate between Lichen and psoriasis), Parapsoriasis lichenoides, including Parakeratosis variegata of Unna, and Lichen variegatus (Crocker).
Third variety (closely allied to Seborrhœa psoriasiformis), Parapsoriasis in patches, corresponding to Erythrodermie pityriasique en plaques disseminées of Brocq, and of which cases have also been reported by J. C. White and C. J. White.
It is only with the third variety that comparison need be made, the deep colour and very small pattern, like a mosaic of the first two, sharply contrasting with the broad effects as of colour dashed on, in Xantho-erythrodermia perstans.
For the whole group Brocq gives the following characteristics: