ARE ECZEMA AND PSORIASIS LOCAL DISEASES OF THE SKIN, OR ARE THEY MANIFESTATIONS OF CONSTITUTIONAL DISORDERS?

BY

L. DUNCAN BULKLEY, A.M., M.D.,

PHYSICIAN TO THE SKIN DEPARTMENT, DEMILT DISPENSARY, NEW YORK, ETC.

THE suggestion of a local pathology of diseases of the skin is of comparatively recent date, and stands in bold contrast to the older humoralistic doctrine, which ascribed all these diseases to a morbid entity, a materies morbi, seeking exit from the system, and whose escape is beneficial; and the positive demonstration within the present century of a local cause of several cutaneous maladies (as dermatitis, the parasitic affections, etc.) which had, for ages, been regarded as expressions of blood states, is an achievement of which modern medicine may justly be proud. This discovery of a local origin of certain skin lesions, and the fact of the resemblance between some of the forms of dermatitis and the eruptions of impetigo, lichen, eczema, etc., have led some to claim, still further, that most, if not all, of the diseases affecting the skin are either the results of local external causes, or are local diseases originating in idiopathically deranged action of the elements of the skin; a view, the adoption of which has undoubtedly been promoted by a natural reaction from the too exclusive, humoral doctrines previously entertained.

It need hardly be said that in arguing a constitutional origin and nature of eczema and psoriasis, I do not desire at all to return to the older humoralistic doctrine of disease, but seek to keep entirely within the bounds of recent chemical physiology and pathology, while at the same time I by no means ignore the importance of local cell-action, as will appear later. Nor does the recognition of a constitutional nature of eczema and psoriasis, by any means necessitate a belief that it is dangerous to check or remove these diseases by local measures, for experience has proved the contrary; it does, however, demand an investigation of internal causes, and a removal, as far as possible, of systemic disorders, since thereby elements of disease are removed and the general system benefited, while the eczema and psoriasis are cured.

In the further presentation of the subject of the nature and origin of eczema and psoriasis, it will be advisable to separate the two diseases more or less; I will, therefore, in each instance speak first of eczema, and then make the application to psoriasis; because, although they resemble each other in many important particulars, and have many points of contact, their dissimilarities are such as to cause confusion if they are in every instance spoken of together.

The local pathology of eczema and psoriasis has rested largely on three grounds: first, on the results obtained in the local treatment of these and other diseases of the skin, especially in the larger hospitals in Europe, notably those in Vienna; second, upon microscopical researches in histology; and, third, as far as relates to eczema, on a clinical and micro

scopic study of the artificial eruptions produced on the skin by irritating substances, idiopathically and experimentally. We will dispose of the last of these first.

Now, while there is as yet no absolute proof that the pathological process excited artificially in the skin differs essentially from that taking place in acute eczema, we need not conclude that eczema is of local origin because its eruption resembles artificial dermatitis. If we accept one artificial eruption as eczema, we must accept all as such, from the large blisters following cantharides, heat, and cold, to the discrete, pustular eruption caused by croton oil or tartar emetic, or the slight erythema of the mildest irritant. Moreover, many of these artificial eruptions resemble erysipelas even more than they do eczema, and yet there will be few who will hold that true erysipelas is a local disease of the skin; again, the eruptions of croton oil and tartar emetic resemble those of smallpox and syphilis, without this being any argument against the constitutional nature of these latter, while the eruptions produced by the insect in scabies and by lice are frequently confounded with eczema. These lesions are all purely local, there is simply a local response of the cells and capillaries of the over-stimulated part; they are all but forms and varieties of inflammation of the skin, and are properly termed dermatitis, and bear no more relation to eczema than does the inflammation of a sprained joint to true rheumatism. In a very small proportion of persons, such irritations may become the starting point of true eczema, but in them I believe that the elements of the eczematous diathesis may always be discovered. A demonstration of the essential difference between these artificial eruptions and eczema is shown by the fact that it is not uncommon to induce dermatitis, as by a blister, for the cure of chronic eczema, as also of psoriasis.

It is necessary, therefore, in the present study to remember the distinction between eczema and dermatitis, for undoubtedly much that has been treated for the former is but the latter, and of course no argument can be drawn from therapeutical results obtained in dermatitis as to the local nature of eczema. In regard to psoriasis also, we have to clearly exclude, not only the scaly syphiloderm, but also all syphilitic influence; true psoriasis, the lepra of Willan, has nothing to do with syphilis, not even in the way of a later hereditary transmission, as has been suggested, nor must it be in any way confounded with the dry, scaly forms of eczema, or with the true leprosy, the elephantiasis of the Greeks.

Before proceeding systematically to examine the several points regarding the local or constitutional natures of these diseases, let us consider, for a moment, the question of the possibility of a double origin of the diseases under consideration, whether they can own two natures, being sometimes local and sometimes constitutional. In regard to the skin lesions in the contagious exanthemata and syphilis, no question exists that their origin is solely and always due to the introduction of a poison, which acts through the system, and that the cutaneous manifestations are but one exhibition of their effect. Passing now to such general diseases as gout and rheumatism, whose etiology is more deeply hidden, we do not doubt that the local phenomena observed in each are always the result of the same constitutional condition, some of the earlier links in the chain of cause and effect being recognized in functional derangement of certain organs, and a consequent sub-oxidation or imperfect elaboration of the elements of food, and an absence of healthy disintegration of tissue; and

when we speak of cold or external injury as being the cause of gouty or rheumatic inflammatory action in a part, we understand readily that it is only intended to signify that it was the exciting cause, which determined that that particular spot should be affected, or that the disease should develop at that particular time. The same line of thought might be extended to other diseases, showing that it is irrational to deny the constitutional origin of a disease unless its local nature can be established in a manner answering every requirement, as is the case in the parasitic diseases of the skin; quite as impossible is it to exclude local causation, when the constitutional nature fails to account for every condition.

Great error has, therefore, been made, I believe, by those who look only or mainly at the local causes, and argue therefrom a local nature of eczema, they forgetting the established principles in general medicine in regard to predisposing and exciting causes of disease. This is verified. by the fact of the difficulty of producing a true eczema artificially, at will, in a person not subject thereto either in self or family (if indeed it can ever be done), and the impossibility of inducing a psoriasis by any local means.

Our conclusions then, thus far, are that eczema and psoriasis cannot be both local and constitutional diseases, that is, either exclusively, according to the case; and that the eruptions resembling eczema, artificially produced, are either ordinary dermatitis, with a strong tendency to spontaneous recovery, or are true eczema in eczematous subjects, in whom the exciting cause, instead of occurring in the ordinary way, has been artificially supplied, just as a gouty person might, by measures voluntarily applied, induce a true gouty inflammation of a joint. As before stated, we know of no claim to the production of psoriasis by local measures alone.

In the present study of the question as to whether eczema and psoriasis are local diseases of the skin or manifestations of constitutional disorders, I propose to develop the following points:

(1) The nature of the eruption in disorders of the skin which are recognized to be constitutional, as the contagious fevers, syphilis, etc., drawing a comparison between eczema and psoriasis and these affections, and showing their points of difference.

(2) The nature of local diseases of the skin.

(3) The microscopic anatomy of eczema and psoriasis, with a view of comparison with that of the local skin diseases on the one hand, and with that of the constitutional on the other.

(4) The clinical history of eczema and psoriasis, in so far as they bear on the question, the points considered being (a) age, (b) sex, (c) location of eruption, (d) relapses, (e) hereditary transmission, (f) gouty and rheumatic symptoms, (g) urinary disturbances, (h) bronchitis, etc.

(5) The clinical history of some local diseases, to show the differentiating elements between constitutional disorders and those believed to be local, as epithelioma, verruca, keloid, parasitic and mechanical diseases of the skin, etc.

(6) The effect of local treatment, and how far the success of local measures necessitates a belief in the purely local nature of the disease.

(7) The effect of constitutional treatment, and the internal and general measures of service in eczema and psoriasis, to show how far their effect proves that the diseases which they remove are constitutional.

(1) In comparing eczema and psoriasis to the acknowledged constitutional disorders affecting the skin, contagious fevers, syphilis, etc., we must not, of course, press the similarity too far. We find, however, certain resemblances, as in the symmetry of development of the lesions, for eczema, if uninfluenced by local causes, will, when carefully studied, be found to exhibit this almost as clearly as psoriasis, whose bilateral disposition is so striking; the peripheral mode of spreading of eczema resembles much that of erysipelas, and the scattered eruption of psoriasis corresponds much to the mode of development of other exanthematous diseases, including syphilis. Eczema also is not infrequently attended with fever, in its more acute and general forms, and on the full, recent development of psoriasis there is more or less of malaise and prostration, and probably fever. The characters of the lesions in eczema and psoriasis are not entirely unlike those of constitutional diseases, which are marked by, first, congestion; second, exudation; and, third, if these former have been sufficiently severe, desquamation. The lesions of eczema and psoriasis are also superficial, and rarely, if ever, do they leave cicatrices, when uncomplicated.

(2) In contrast with these stand the characteristics of local diseases of the skin, marked by their utter want of symmetry (unless accidental), their extension depending either on a recognized cause, or being unexplainable, as in keloid, epithelioma, etc.; local diseases very rarely affect the whole integument, or even large portions, unless ichthyosis, of whose true nature, however, we know very little, be granted as such. Local diseases, moreover, acknowledge no constitutional connections nor fever; while, finally, the congestive element of eczema and psoriasis stands in striking contrast to its absence in local diseases, except, of course, where it is called forth by local stimulation. I am well aware that many cases of eczema present a number of the features of local disease, and that psoriasis occasionally is seen quite localized; but this is the exception, whereas it is rare to find exceptions in regard to the local diseases exhibiting any constitutional features; and, as we have concluded that eczema and psoriasis cannot be at one time local and at another constitutional, the weight of evidence, in this comparison, is decidedly in favor of the latter.

(3) The study of the microscopic anatomy of eczema and psoriasis is as yet in its infancy, and throws but little light on the etiology of these diseases; but, for a comprehensive view of the subject, we will briefly recall the main points in their histology, which will be seen to favor the constitutional rather than the local nature of the affections. The first anatomical change in eczema (reasoning from what is observed in artificial eruptions) is capillary congestion, resulting in capillary stasis and exudation in the tissue of the skin, producing more or less oedema. In some instances, not rare with us, the process stops here, or is arrested by treatment, and we have only the erythematous state, followed by moderate desquamation, the result of the impaired nutrition of the outer layers of the skin, a state very similar to the epithelial shedding in scarlatina, erysipelas, or measles.

If the exudation is too great to allow of absorption, it seeks egress through the external layers of the skin, or becomes organized as chronic infiltration. Biesiadecki believes that the fluid of eczema gains exit through certain spindle-shaped cells, which lie between the round and polygonal cells of the rete, these becoming so altered as to convey the Huid, as through direct channels. When the outer surface is still intact,

the hard, horny epidermis resists further progress and a vesicle forms; when the epidermal layer has been dissolved off or ruptured, the fluid oozes from the surface. Charpy' gives a somewhat different account of the genesis of eczema; still regarding the beginning of the disease as being in the corium, and consisting in a congestion of the layer just beneath the papillæ, he believes that the exuded fluid is absorbed by the deeper cells of the rete, in the intervals between the papille; that these cells become engorged until they rupture, whereby alveoles are formed; and that the increase of these alveoles terminates in the production of vesicles, upon the rupture of which cul-de-sacs are formed, whose walls furnish the further secretion.

In chronic eczema, the exuded plasma has become organized, and is seen as cell infiltration of the corium; the papillæ are much enlarged; the lymphatics, both in the papillæ and corium, are increased in size and dilated (Neumann); the blood vessels are sometimes obliterated (Rindfleisch); and even the deepest parts of the skin are involved.

The anatomical and other relations of eczema have suggested to some a likeness between this and catarrh of the mucous membranes, and it may be well here to consider for a moment the nature of the mucous affection called catarrh, in reference to the bearing of this resemblance upon the nature of the diseases now under consideration. First, it must be remembered that it is no more proper to call all inflammations of the mucous membranes catarrh, than it is to name all those of the external integument eczema, or even dermatitis; the term catarrh but signifies. the exudative feature, and the word eczema implies much the same. We have already separated and clearly differentiated many diseases of the mucous membranes, and it is highly probable that future study will show that there are many very different processes included in what is yet called catarrh, and ultimately their nature and origin will, we suspect, be as clearly defined as are now those of cutaneous diseases, or, it is hoped, far more clearly. That this is true may be judged from our present knowledge; thus, we have simple intestinal catarrh caused by the direct irritation of indigestible substances, a mechanical affair corresponding to ordinary dermatitis; we have an incontrollable diarrhoea, or catarrh, from the irritation caused by the circulation of effete substances in renal disease; there is also a mechanical catarrh from portal congestion in cirrhosis; we have also gouty affections of the various mucous surfaces; likewise the catarrhal complications of measles, those of syphilitic origin, etc., and I have long believed that much of the ordinary bronchial catarrh was truly eczema of that surface. Therefore, in likening eczema to catarrh of the mucous membranes, we by no means simplify matters in regard to its local or constitutional nature. Moreover, the common observation of catarrhal affections following a chilling of the surface, does not indicate necessarily their local nature, due wholly to the cold, for we see great differences in the results produced, dependent evidently upon constitutional states, the congestion due to the action of cold on the integument being only the exciting cause.

We will now consider for a moment some views in regard to the local nature of eczema propounded by Dr. Tilbury Fox, in the Lettsomian Lectures for 1869 and 1870. He suggests that the capillary congestion is a consequence of cell activity, arguing that mere capillary excitement

Annales de Dermatologie et de Syphiligraphie. t. iii. p. 100.

2 Eczema, its Nature and Treatment; London, 1870.