Diagnosis

The characters of hydroa bulleux permit always of its being recognized. It is important to establish well the differential diagnosis between this disease and pemphigus. In the former the bullae are small, and do not go beyond the size of a pea; they are further remarkable for the inequality of their size, they occupy regions sufficiently well circumscribed. The bullae of pemphigus are larger - they may attain the size of a nut, or even of a hen's egg; they exist in various parts, and extend sometimes over the chief part of the skin.

The diseases which it in a measure resembles are, urticaria and the various forms of erythema, and perhaps mis­takes might be made between it and the vesicular syphilide, varicella, and variola. As a rule, it has a definite duration, and disappears spontaneously in a few days, and may be accompanied by slight fever. The first phenomenon noticed is a faintly-marked, rosy spot, which is soon replaced by a single vesicle, which may remain intact or may become umbilicated, or may dry up and become an umbilicated crust of a yellowish-white color. Around this vesicle inflammatory changes very soon take place; a zone of a color varying from red to violet, with a well-defined, slightly elevated periphery, forms, and then around this perhaps a ring of small vesicles, which may coalesce and form a circumferential bullae. These spots vary in size from a line to four or five, or even more. There is no hype-raemia between the patches, as the inflammatory action is sharply confined to them. This condition differs from that of herpes phlyctenodes, in which the inflammatory areola is not thus sharply defined. There is usually no pain or itching, merely a little heat or a feeling of tension. The same appearances, somewhat modified, have been observed upon the buccal mucous membrane. The eruption disappears by the fall of the crust, which is formed from the vesicle, and is generally seen in the centre of each patch, and then there remains a more or less well-marked hyperaemia with slight infiltration. The sites of election are the back of the hands, the forearms, face, neck, and also the trunk and lower limbs. It is generally symmetrically developed.


The practitioner may meet with cases in which, with or without some slight antecedents, malaise, or pyrexia, a few scattered spots answering as regards eruptive features to Bazin's hydroa vesiculeux occur - that is to say, a few red irritable spots appear, having in the centre a small oval or roundish bulla, which may enlarge to the size of a split pea, but is generally not so large, arid dies away in the course of a few days. These spots appear on the back of the hands,  the   arms,  the legs,  and the shoulders. The disease may last, by the development of successive crops of solitary vesicles, for ten days or more.

The more exaggerated form of this disease is that in which small bullae are developed rapidly over a large extent of surface, or even the whole body.


In some instances in which this quasi-herpetic or pem-phigoid disease makes its appearance the eruption is preceded by an unusual amount of irritation, and it is complicated or followed by true pruriginosus rash. This is very probably the  disease termed pemphigus  pruriginosus.

We may therefore sum up the foregoing remarks by saying that there is a form of disease which seems to stand midway between herpes and pemphigus, the features of which ally it, now to herpes, now to pemphigus. It may consist of solitary small bullae seated on a red base, and scattered here and there over the body, or the bullae may be surrounded by small vesicles; or these two dispositions of the bullae may be seen in one and the same case, the eruption being localized to a certain part of the body, or generally distributed and accompanied in severe cases by pyrexia and marked constitutional disturbances, which is often the result probably of malarial poisoning. The eruption may recur more or less periodically; and lastly it may be complicated or followed by prurigo, and in that case will answer to the designation of pemphigus pruriginosus.

The characters I have given are sufficient for diagnostic purposes. The only disease with which they might be confounded is urticaria bullosa, and I do not know that any mischief would accrue to the patient from such a mistake.