Part 30

#Describe the clinical appearances of a typical, well developed case.#

Twenty or a hundred or more lesions, varying in size from a pin-head to a silver dollar, are usually present. They are sharply defined against the sound skin, are reddish, slightly elevated and infiltrated, and more or less abundantly covered with whitish, grayish or mother-of-pearl colored scales. The patches are usually scattered over the general surface, but are frequently more numerous on the extensor surfaces of the arms and legs, especially about the elbows and knees. Several closely-lying lesions may coalesce and a large, irregular patch be formed; some of the patches, also, may be more or less circinate, the central portion having, in a measure or completely, disappeared.

#Give the development and history of a single lesion.#

Every single patch of psoriasis begins as a pin-point or pin-head-sized, hyperæmic, scaly, slightly-elevated lesion; it increases gradually, and in the course of several days or weeks usually reaches the size of a dime or larger, and then may remain stationary; or involution begins to take place, usually by a disappearance, partially or completely, of the central portion, and finally of the whole patch.

#Describe the so-called clinical varieties of psoriasis.#

As clinically met with, the patches present are, as a rule, in all stages of development. In some instances, however, the lesions, or the most of them, progress no further than pin-head in size, and then remain stationary, constituting psoriasis punctata; in other cases, they may stop short after having reached the size of drops--psoriasis guttata; in others (and this is the usual clinical type) the patches develop to the size of coins--psoriasis nummularis. In some cases there is a strong tendency for the central part of the lesions to disappear, and the process then remain stationary, the patches being ring-shaped--psoriasis circinata; and occasionally several such rings coalesce, the coalescing portions disappearing and the eruption be more or less serpentine--psoriasis gyrata. Or, in other instances, several large contiguous lesions may coalesce and a diffused, infiltrated patch covering considerable surface results--psoriasis diffusa, psoriasis inveterata.

#Is the eruption of psoriasis always dry?#

Yes.

#What course does psoriasis pursue?#

As a rule, eminently chronic. Patches may remain almost indefinitely, or may gradually disappear and new lesions appear elsewhere, and so the disease may continue for months and, sometimes, for years; or, after continuing for a longer or shorter period, may subside and the skin remain free for several months or one or two years, and, in rare instances, may never return.

#Is the course of psoriasis influenced by the seasons?#

As a rule, yes; there is a natural tendency for the disease to become less active or to disappear altogether during the warm months.

#What is known in regard to the etiology of psoriasis?#

The causes of the disease are always more or less obscure. There is often a hereditary tendency, and the gouty and rheumatic diathesis must occasionally be considered potential. In some instances it is apparently influenced by the state of the general health. It is a rather common disease and is met with in all walks of life.

#Is psoriasis contagious?#

No. In recent years the fact of its exhibiting a family tendency has been thought as much suggestive of contagiousness as of heredity.

#What is the pathology?#

According to modern investigations, it is an inflammation induced by hyperplasia of the rete mucosum; and it is beginning to be believed that this hyperplasia may have a parasitic factor as the starting-cause.

#With what diseases are you likely to confound psoriasis?#

Chiefly with squamous eczema and the papulo-squamous syphiloderm; and on the scalp, also with seborrha. It can scarcely be confounded with ringworm.

#How is psoriasis to be distinguished from squamous eczema?#

By the sharply-defined, circumscribed, scattered, scaly patches, and by the history and course of the individual lesions.

#In what respects does the papulo-squamous syphiloderm differ from psoriasis?#

The scales of the squamous syphilide are usually dirty gray in color and more or less scanty; the patches are coppery in hue, and usually several or more characteristic scaleless, infiltrated papules are to be found. The face, palms, and soles are often the seat of the syphilitic eruption; and, moreover, concomitant symptoms of syphilis, such as sore throat, mucous patches, glandular enlargement, rheumatic pains, falling out of the hair, together with the history of the initial lesion, are one, several, or all usually present.

#How does seborrha differ from psoriasis?#

Seborrha of the scalp is usually diffused, with but little redness and no infiltration; moreover, the scales of seborrha are greasy, dirty gray or brownish, while those of psoriasis are dry and comonly whitish or mother-of-pearl colored. Psoriasis of the scalp rarely exists independently of other patches elsewhere on the general surface.

That variety of seborrha, commonly known as eczema seborrhoicum, presents at times, both on scalp and general surface, a strong resemblance to psoriasis, but the character of the scales and distribution of psoriasis, as above stated, are distinguishing points; seborrha, moreover, favors hairy surfaces and in extensive examples the scalp, eyebrows, sternal, and pubic regions rarely escape.

#How does psoriasis differ from ringworm?#