The proper treatment of cutaneous diseases is dependent in a large measure upon correct diagnosis. Otherwise the management of the case is apt to be haphazard and unscientific. It is not sufficient to say that the disease is papular, pustular, etc., but it must be recognized as a clinical entity which embraces not only its initial manifestations, but all its changes, terminating in the natural ending of the disease. Provided the investigator has the proper amount of text-book knowledge supplemented by the experience of clinical observation, he should be able to make a correct diagnosis in the great majority of cases. If he fails in this particular, it is either due to negligence in the examination or less often to the rarity or peculiarity of the disease in question. A diagnosis should never be made without sufficient examination and even the most expert may require repeated examinations before arriving at a definite conclusion. An effort should be made to see things as they are and not hunt for facts to fit a name, which is the last if not the least in importance. As sight and touch form the chief means of examination, the patient should be seen in good daylight. Direct sunlight or artificial light modify color, especially the shades of yellow, to such an extent as to be at times misleading. If possible, the room should have walls of neutral tint so as not to reflect their color upon the skin. The temperature of the room should be warm enough to permit partial or entire exposure of the skin surface without discomfort or injury to the patient. In this particular it is often best to insist upon seeing the whole or at least the greater part of the eruption, because the disease may be atypical in one location and characteristic in another.
While the subject of special diagnosis will be considered in connection with separate diseases, there are general principles which can be studied profitably, as illustrating the collecting and grouping of facts for the purpose of diagnosis. To accomplish this purpose, systematic work will well repay the investigator, for the apparent ease with which an expert diagnostician arrives at his conclusions by a seemingly rapid and superficial survey of the symptoms is only accomplished by long practice, frequent opportunity and systematic methods. Inquiries that enable the investigator to make a diagnosis can be tabulated on sheets made for that purpose. Usually these records are too complicated to be appreciated by the student or too detailed to be used by the practitioner and only interest the specialist. In my service at the Metropolitan Hospital, I employ an exhaustive four-page history which, in brief, includes statistical data, hereditary history, antecedent personal history, a sheet with suggestive procedure which is followed in the examination of the patient and his eruption, microscopic and bacteriological examinations, discharge or mortuary record, final or corrected diagnosis and resulting scientific conclusions. However, it is not necessary to amplify these details, but rather to illustrate the relationship existing between the various factors that contribute to a knowledge of etiology and hence establish a diagnosis. The same facts which enable the physician to distinguish one disease from others furnish important indications for treatment, and together with a knowledge of the probable therapeutic effect form the basis for an opinion as to the probable course or termination of the disease (prognosis). Following is a graphic arrangement (Crocker’s grouping, modified) of the diagnostic elements and their relation to further essentials in practice:
Patient- Age, sex, nationally, occupation personal health, habits of living, family history.
Disease Symptoms and their peculiarities.
Lesions Character, evolution, size, shape, color, distribution, effects.
To explain the above, a few words concerning the patient, his disease and its lesions are necessary. Before proceeding to this brief explanation, it should be remarked that patience and tact are often required to elicit the facts, because inaccuracies of description and misuse of technical terms must be expected of the layman. The patient’s family and personal history, age, sex, nationality, civil condition, occupation, habits of living, general appearance and systemic or local disturbances should be noted. Inasmuch as these items have been discussed in the chapter on etiology, to which the student is referred for particulars, it is only necessary to emphasize a few items. Hereditary influence may be noted in the family history and particular attention should be paid to rheumatic, alcoholic, nephritic, diabetic, cancerous and syphilitic tendencies as well as the matter of drug habits. The question of previous attacks of the same disease, as may be noted in psoriasis, eczema and urticaria, is suggestive. Antecedent personal history should particularly disclose if the patient has had any of the exanthemata, syphilis, erysipelas, gonorrhoea, tuberculosis, typhoid fever, diabetes or pronounced gastrointestinal or mentonervous disorders. Habits of living should be carefully investigated because they frequently cause anemic or plethoric conditions practically diathetic in nature.
The disease manifests itself by general or local symptoms which may precede or attend the eruption. There may be constitutional disturbances during syphilis, leprosy, etc.; pronounced fever in most of the inflammatory, contagious skin diseases; itching in eczema and the parasitic dermatoses; burning or neuralgic pains in zoster. Some of these sensations are quite diagnostic, added to the clinical history. The same may be said of the odor attending some eruptions, mouse-like in favus, typically offensive in syphilitic, variolous and gangrenous ulcerations.
The duration of the eruption may aid in diagnosis. It is not always easy to arrive at the real facts as regards the normal duration of disease because some conditions disappear spontaneously while others can be relieved as quickly by the proper treatment. However, there are some morbid conditions that are typically acute, subacute or chronic. Among the eruptions of short duration, rarely exceeding a few weeks, may be mentioned dermatitis medicamentosa, dermatitis venenata, ecthyma, erysipelas, many of the erythemata, furunculus, herpes zoster, impetigo contagiosa, miliaria, and ringworm of the non-hairy surface. Among the eruptions of moderate duration, rarely exceeding two months, may be mentioned erythema multiforme, pityriasis rosea, pompholyx, purpura and the secondary syphilids. Many of the so-called chronic diseases are, strictly speaking, recurrent. Among these may be mentioned eczema, psoriasis, acne, seborrhea, tuberculosis cutis, lupus erythematous, tinea versicolor, erythrasma and many of the new-growths and neoplasms.
The course of the eruption is frequently characteristic. Thus it may appear all at once as in herpes; in crops as in varicella and pemphigus; continuously as in acne; by progressive spreading as in many cases of eczema and in parasitic diseases. It is well to notice the change caused in an eruption by scratching or by purely external methods of treatment and to note if the present lesions are primary or changed by past and present stages of evolution. While the collection of facts relating to a patient may be for the purpose of making a diagnosis, frequently the cause of the disease will be learned at the same time. It is in this particular that modern medicine is superior, inasmuch as the microscope and other instruments of precision enable the clinician to examine in detail parasites, sections of living tissue or morbid growths, and specimens of urine, sputum, feces, milk and blood. Bio-logic reactions should also be mentioned in this connection.
Lesions, viewed from the standpoint of their peculiarities, afford the real basis for diagnosis, but facts regarding the patient and his disease tend to sustain or modify this information. The variety of lesion is important; whether papules, as in lichen planus and prurigo; papulopustules, as in acne; wheals, as in urticaria; or multiple lesions, as in syphilis and many cases of eczema. The presence or absence of induration in or about the lesions; signs of inflammation, as heat, swelling and color; or color due to other pathological changes, as the yellow crusts of favus, the violet-red of lupus vulgaris, should be noted. In the earlier stages of an eruption, lesions are more likely to show typical forms, unchanged by evolution or artificial influences. Even when such changes have occurred, the edges of an active patch will frequently exhibit the original form of lesion. Secondary lesions may indicate the primary form and show pathological features and methods of evolution, as the yellow crusts from previous pustulation; the light yellow, brown or blackish crusts from the drying of serous, seropurulent and bloody discharges; or the ulcers from degeneration of infiltrated growths like syphilis and lupus vulgaris.
It may be possible to inquire further and note the effects of lesions, such as the pigment stains remaining after syphilis, lichen ruber and acne; the disfiguring scars of scrofuloderma and lupus vulgaris; the smooth, delicate cicatrices of superficial syphilitic ulcerations. Care must be taken to differentiate lesions natural to the morbid process and those which result from external influences such as crusts, excoriations and wheals from scratching, or from changes brought about by soothing, stimulating, destructive or surgical treatment. Again, it should be remembered that two or more diseases may coexist, and one of them may more or less completely mask the others; thus eczema may be engrafted on a lupus erythematosus, syphilitic ulceration disguised as lupus vulgaris; scabies complicate a psoriasis; or impetigo change the appearance of a varicella. Certain lesions are pathognomonic whenever found in association with other signs of a disease. Such are the sulphur-yellow cups of favus; the broken stubble hairs of tinea capitis; the burrows of the itch mite; the ova on the hairy parts, and the hemorrhagic points on the non-hairy parts, in pediculosis; the flat, glistening papules in lichen planus; and the apple-jelly nodules of lupus vulgaris.
The evolution of a lesion may assist in differentiating it from similar lesions. Lesions may spread by peripheral extension and, at the same time, clear in the center as seen in ringworm of the body and some types of erythema multiforme, or without tendency to clear centrally, as in dermatitis seborrhoica. When adjacent rings expand to meet each other, the sections in contact disappear but the free border continues to extend, forming irregular curves and figures as in some cases of psoriasis.
The distribution and extent of lesions may be characteristic. Symmetrical arrangement of lesions is usually due to constitutional influences or to the presence in the circulation of irritants or poisons. The lesions of the exanthemata and those from the ingestion of the iodine salts are examples of this feature. Unsymmetrical distribution of lesions is largely due to agents primarily acting upon a local part as the local infection of lupus vulgaris, or through the nerves of a part as in zoster. Universal and generalized distributions, may be noted as specified below. The lesions of some skin diseases commonly begin in certain regions; for instance, dermatitis seborrhoica upon the scalp, psoriasis upon the extensor aspect of the elbows and knees and thence by preference to the other extensor surfaces. The following table, showing the tendency of cutaneous diseases to develop in certain regions of the body surface, is included because it is most helpful in diagnostic procedure.