Synonyms. Lepra alphos, alphos, psoriasis vulgaris.
Psoriasis is a
common chronic, recurrent, inflammatory disease of the skin characterized by
rounded, circumscribed, erythematous, dry scaling patches of various sizes covered
by grayish-white or silvery-white, imbricated and abundant scales. The lesions
have a predilection for the scalp, nails, extensor surfaces of the limbs and
the sacral region. The eruption is usually symmetrical and may vary from a
solitary spot to countless patches. The eruption usually develops slowly but
may be exanthematic, with the sudden onset
of numerous guttate lesions, or may consist of a few inveterate patches.
Subjective symptoms such as itching or burning may occasionally be present. The
cause of the disease is unknown.
The
early lesions are guttate erythematous macules or maculopapules, which from the beginning are covered with
dry silvery scales. By peripheral extension and by coalescence, the spots
increase in size, and through the accumulation
of scales they become thicker. Nummular (coin-shaped) lesions are
common. In this variety certain distinctive features may be easily
demonstrated: (1) The scales are micaceous, and looser toward the periphery of
the patch while adherent at the center; (2) upon removal of the scales,
bleeding points occur. After the patches reach a diameter of about 5 cm., they
cease spreading and tend to undergo involution in the center, so that annular,
lobulated and gyrate figures are produced.
Old
patches may be thickened and tough, and covered with lamellae of scales so that
they resemble the outside of an oyster shell (psoriasis ostracea). Various
other descriptive terms are applied to the diverse appearances of the lesions:
psoriasis guttata, in which the lesions are the size of drops; psoriasis
follicularis, in which tiny scaly lesions are located at the orifices of the
pilosebaceous follicles; psoriasis figurata, psoriasis annulata, and psoriasis
gyrata, in which curved linear patterns are produced by central involution;
psoriasis discoidea, in which central involution
does not occur and solid patches persist; psoriasis rupioides, in which crustaceous
lesions occur resembling syphilitic rupia; psoriasis arthro-pathica, a
particularly inveterate form associated with chronic arthritis. This is a
polyarthritis of the small joints of the hands and feet.
Extensive cases of long duration may develop a universal erythroderma.
In a review of over 2200 cases of psoriasis, Coeckerman and O'Leary were able
to find 22 cases (about 1 per cent) of erythroderma psoriaticum. Auto-sensitization may account for this
universal exfoliative erythroderma. Rarely,
bullous lesions have been observed during acute exacerbations, and cases
have been reported in which generalized eruptions of flaccid bullae later developed features characteristic of
psoriasis. Pustular psoriasis was described by Schaffer in 1921 and later by
MacLeod. The typical psoriatic patches become covered with small pustules. This
change sometimes precedes the development of generalized exfoliative
dermatitis. Pustular psoriasis of the extremities, as described by Barber and
Ingram, is a different clinical expression of the disease, which is considered
separately. Flexural psoriasis is a definite regional type.
The course of
psoriasis is inconstant. It usually begins on the scalp or on the extensor
surfaces of the elbows, and may remain localized to the original region for an indefinite period, or completely disappear,
recur, or spread to other parts. The beginning may be over the sacrum,
where the patch slowly extends to form
an inveterate lesion. At other times the onset is more sudden and widespread,
as already described; or in other cases the first lesions may be limited to the
fingernails.
One of the
chief features of psoriasis is its tendency to recurrences. These are commonly
manifest over and over again throughout the lifetime of the patient. Rarely, however, psoriatics may remain completely
free of the disease for years, and may be considered, in at least a
practical sense, cured. On the scalp it
does not cause loss of hair. The lesions are sometimes easily irritated—even the chronic ones—and when this takes
place they are liable to spread by the development of satellites, or new
spots in other regions. In acute guttate or
nummular spreading eruptions, if irritating remedies arc applied, a
generalized exfoliative dermatitis may result. Although psoriasis
affects both children and adults, the course of the disease is comparatively
mild in children.
The Koebner phenomenon is the appearance of typical lesions of
psoriasis at sites of
injuries. Tins is a characteristic feature of the disease and accounts for the
frequent appearance of typical psoriatic patches on scars and at sites of
operations and burns. Occasionally the initial patch is upon the site of such a
trauma. In the presence of early lesions, new lesions can be produced by
scratching the skin. The Koebner phenomenon occurs in many other skin diseases,
such as lichen planus, lichen nitidus, verruca plana and infectious eczematoid
dermatitis.
The
various theories concerning the etiology of psoriasis are too voluminous
to be covered adequately in the space permitted. Present tendencies favor a metabolic disturbance of
phosphorylation, often inherited, which may
be influenced by stress and focal infection. There is a history of family incidence in about 25% of the cases. The
frequent association of this combination of factors with arthritis is
noteworthy.
