Perhaps one of the greatest errors committed in diagnosing cutaneous diseases is the dealing with them in a piecemeal manner. It is the universal expectation of the student to be able to diagnose a disease of the skin from merely looking at it. Many a student, if asked with a patient before him, What is that disease? will look,- and, it may be, look closely- and then make his diagnosis and give the thing a name. In no other class of disease would he do that. He would obtain the objective, and the subjective symptoms; and use every means at his command for physical examination. It is of equal importance that he exhibit a like careful comparison in lesions of the skin.
One of the first cares of the dermatologist should be to distinguish in diagnosis between primary and secondary phenomena. The one set are of course essential points of the disease, and the secondary results may, if care be not taken, be elevated to the rank of important items. For instance: In the case of an erythema, in connection with long-continued congestion, more or less thickening may occur; if this be not clearly perceived to be an accidental occurrence, the diagnosis becomes difficult. Take the case of pityriasis rubra, a disease in which the whole skin becomes intensely hyperaemic with free shedding of scales. If this be properly treated it will disappear, and leave not a trace. It may be unaccompanied throughout its course by any thickening of the papillary layer; but if it continues a long while this layer may be thickened, and then there are present hyperaemia, papillary hypertrophy, and scaliness, as in psoriasis; and the diagnosis between pityriasis rubra and psoriasis could not be made from the mere surface appearances and alternations only. But the two things clinically are wholly different. This shows the importance of attending to the primary elementary lesion and the history and course of diseases.
Again, in searching for the earliest stage of disease when that occurs in patches, it is necessary to go to the edge of the disease since it there presents its most recent characters.
The typical course and characters of any disease may be masked by the co-existing development of a second disease, and here the interminglage of the features of the twain will be detected, as in urticaria and scabies or purpura; scabies and syphilis;eczema and scabies; eczema and psoriasis, and the like. The capriciousness as regards the appearance and disappearance of an eruption of an erythmatous type, is suspicious of urticaria. Multiformity means that a disease is complicated, unless it be scabies or syphilis.
As regards the temperament, the dermatologist is generally enabled to say at a glance whether a patient is of full habit and likely to have a loaded system-especially the case in women; whether there be organic disease, or if there be a dyspeptic habit, or an ill-fed system, that signifies debility. If lymphatic, the patient is prone to eczema, impetigo, intertrigo, the pustular aspect of scabies and ringworm; if gouty, the scaly disease, chronic eczema and lichen agrius; if rheumatic, erythema nodosum; if strumous, eczema, lupus; if florid, psoriasis especially. There is also the cancerous cachexia, and in nervous subjects various hyperesthesia engrafted upon ordinary eruptions. Red-haired subjects are declared to be very liable to pityriasis of the scalp.
Some eruptions are more or less periodic in their occurrence, as in the case of pemphigus, but the dermatologist should remember that in districts where malarious disease is common, a disease not usually possessing periodic features may sometimes be so influenced that its eruption occurs in a periodic manner, or the febrile disturbance by which it is accompanied may show itself in periodic outbursts.
Psoriasis, eczema, and syphilitic disease are essentially those which recur.
Occupation exerts considerable influence in some lesions of the skin. Cooks are particularly liable to eczema and erythema, and bakers, grocers and bricklayers to lichen about the backs of the hands; chimney-sweepers are liable to epithelioma of the scrotum; cotton-workers to urticaria; butchers and graziers to whitlow, boils and malignant pustule and ecthyma; cavalrymen and shoemakers to eczema marginatum in the fork of the thighs; young women who come from the country and have the full diet fare of the city servants and those who change their mode of life, so that it entails more exercise and better living, get an overloaded system that shows itself in erythema papulatum, erythema nodosum, or impetigo.
The age of the patient is very important. During the first six weeks of life congenital syphilis develops itself; intertrigo, eczema of the scalp, and seborrhoea capillitii also occur about the same time. Syphilitic pemphigus occurs, it is said, before the child is six months old, not afterwards; during the first few months and up to and through the period of dentition, strophulus and eczema are met with. Cancer (epithelioma) is a disease of late life-it does not occur before thirty, generally about sixty and beyond. Lupus is a disease which commences in early and young life, and the same may be said of syphilis. The parasitic diseases occur in the young, rarely after twenty-one years of age. Herpes circinatus is the form seen in adult life. In old people, phthiriasis, ecthyma cachecticum, pemphigus, and pruritus, with cancer and rodent ulcer, frequently occur.
We should have some rules as to the mode of studying skin diseases. The following are probably the best; they are taken from Fox:
1. The observer should always strip his patient so that the disease may be exposed to the fullest extent compatible with a due regard to the proper feelings and sensitiveness of the individual. To be satisfied with seeing a bit of a patch of disease in this spot, or just a spot or two there where the malady is most marked even, is often to run great risk of arriving at an erroneous diagnosis, if not to actually make one, certainly to miss the recognition of transitional stages, which are of the utmost importance in determining the general character and often the exact nature of a disease.
2. It is of much importance that mere stages of diseases should be regarded as stages and nothing else. Diseases must be dealt with in their entireties. Where the whole of a disease is made up in any particular instance of certain stages, in estimating the nature and characteristics of that disease one stage must not be regarded in particular-be thrust into undue prominence-at the expense of others. The several stages together constitute the disease.
3. A clear distinction should be drawn between essentials and accidentals. For instance, the essence of scabies is the acarus in its furrow. All else that follow-the follicular irritation, improperly called lichen, the ecthyma, the urticaria, which may occur in many different diseased states of the skin- is accidental, and due to the irritation and the scratching practiced.
4. It should be a point with the dermatological student to make as little as possible of mere superficial appearances and changes, because these are brought about as the result of, and are indeed often secondary to, more important and primary changes in the deeper parts.
5. It is important to pay special attention, as far as possible, to the primary anatomical seat of the disease. What the primary seats of individual diseases are, so far as regards cutis, cuticle, follicles, and the like, I shall discuss in another place in speaking of elementary lesions and the individual diseases themselves.
6. Special attention should be paid to the fact of the character of an eruption being permanent, or transient, or interchangeable. The case of lichen planus may be taken to illustrate this point. In it the characteristic lesion is a red flattened papule covered by the minutest scales. This is the sole lesion present. The papule never changes into a pustule or a vesicle; but not so it is with the papule of eczema or variola. The tendency of a syphilitic papule is to become oftentimes a pustule or tubercle, which gives place to an ulcer, and so on. The eruption as a whole may be again capricious, appearing and disappearing suddenly, often in the course of a few minutes. This feature in itself is almost diagnostic of urticaria.
7. Those who are studying skin diseases should observe whether an eruption be uniform or multiform in character. Multiformity implies (a) the co-existence of two or more diseases, in which case there will be present the features of the two or more diseases commingled; or it implies (b) the existence (I) if the lesions be inflammatory-that is, if pustules or vesicles be present, of scabies, or (2) if the lesions be degenerative, if ulcers and suppurating tubercles, for example, be present, of syphilitic disease. The difference between the two main classes of cases, the complicated disease on the one hand and scabies and syphilitic on the other, being that in the former there are no transitional stages observed, as in purpura urticans, pemphigus pruriginosus, impetigo and scabies; syphilis and scabies, etc.; whereas, in the latter class, they are present as between the papules, vesicles, and pustules of scabies, or the papules, tubercles, pustules and ulcers of syphiloderma. Multiformity as it exists in scabies and syphiloderma. Multiformity as it exists in scabies and syphilitic eruptions- relates in each case to such different kinds of eruption, and the multiformity moreover in complicated or co-existent diseases is seen to be due to the commingling of such distinct lesions without transitional forms that the character of multiformity becomes at once a very reliable guide in diagnosis; of course, other things help, as rest, development, etc., but multiformity is a good rough test of syphilis, scabies, or complicated diseases.
