208                                      INFLAMMATIONS

PRURIGO

Synonyms.—Fr., Strophulus prurigineux; Ger., Juckblattern.

Definition.—Prurigo is a rare chronic, inflammatory disease,
beginning in early life, characterized by discrete, pin-head to small
pea-sized, solid, firmly seated, slightly raised, pale-red papules, usually
appearing primarily on the tibial surfaces, and accompanied by intense
itching and more or less general thickening of the affected skin.

Symptoms.—There are two varieties usually described, prurigo
mitis and prurigo ferox (also called prurigo agria), which, however,
really represent respectively the mild and severe types of the disease.
In many cases there is a preliminary stage of some months in which
itchiness and the typical wheals and papules (urticaria papuJosa) of
urticaria appear from time to time or more or less continuously; and
for some time after the typical lesions of prurigo have appeared wheals
may now and then be seen. The disease proper begins with the appear­
ance of pin-head-sized papules, which may be pale red in color, or even
the same color as the skin. They appear almost invariably over the
anterior aspects of the legs below the knees, and at first they can scarcely
be seen, but can be felt by passing the hand over the surface. Itchiness
of the parts usually first attracts attention. Later, from natural growth
and from scratching, the lesions are noted to be somewhat larger and
pale red or red in color, and some or many covered with minute blood-
crusts. They may be in moderate quantity or exceedingly numerous
and rather thickly set, but there is no tendency to grouping. At the same
time or later lesions present themselves on the extensor surfaces of the
forearms, and gradually or rapidly upon other parts. In mild cases the
flexor surfaces are scarcely affected, and even in severe type the flexures
of the joints, such as the poplitea, axilla, etc, and the palms remain free
from papules. In severe cases the eruption may be more or less general,
and the face also shows some involvement; the scalp is usually free, but
the skin is dry and the hair lusterless. The disease is most marked on
the extremities, and more especially on the lower half; and the upper
extremities less severely than the lower. The buttocks and trunk also
show decided involvement in severe cases. The skin becomes dry, on
the worse parts thickened and hard and rough, and exhibits branny scali-
ness; the hairs are rubbed off or broken; and the perspiration is prac­
tically suspended. The color is a pale red to a red. The superficial
lymphatic glands, especially the inguinal, show enlargement, some­
times of a pronounced character. From the intense itching, excoria­
tions and long and deep scratch-marks, with resulting slight scars, are
produced, and from the long-continued irritation pigmentation results.
In extreme, neglected cases it is not uncommon to see impetiginous
and ecthymatous lesions interspersed; distinct eczematous conditions
are at times superadded. New crops of papules may appear from
time to time, and the subjective symptoms at such periods become still
more intense. In some instances (prurigo mitis) the disease is much
less pronounced, and consists of scattered, deep-seated papules, chiefly
over the extensor surfaces of the limbs, especially the lower; and in

PRURIGO

209

these cases the mild aspect continues throughout. In fact, usually
the type, as regards severity, is established from the start, although
neglect, poor food, and bad hygiene lead to aggravation. As a rule,
the disease is worse during the cold season.

Etiology.—The disease usually has its beginning in the first few
years of life. It is by far most common in Austria and Hungary, among
the poorer classes, and it is relatively more frequent in the Hebrew
race and in males. Mild types are sometimes seen elsewhere. It is
extremely rare in this country, and when observed is usually in immigrant
subjects, as in the cases reported by Wigglesworth,¹ Campbell,² Zeisler,³
and Taylor.⁴ It is, in its milder types, less rare in England. Occasion­
ally chronic papular eczema cases closely resembling the mild varieties
are observed; and doubtless many of the milder cases of prurigo are con­
sidered, and perhaps are, examples of what is generally recognized as
urticaria papulosa. It is not contagious, and heredity does not seem
to be a factor. It develops, as a rule, in those in poor general health.
Neglect, lack of proper food, and bad hygiene are apparently influential.
Climatic conditions may also be in a measure etiologic The essential
cause, whether neurotic, toxemic, or parasitic, is not known; the neurotic
view predominates.

Pathology.—The true nature of prurigo remains obscure. There
is still much divergent opinion, on reviewing which J. C. White⁵ expressed
the following conclusion: One cannot go further than accept the existence
of a condition of early childhood, allied to pruritus and urticaria in its
visible manifestations, and not to be positively distinguished from
them in its first stages, often becoming in certain parts of the world a
chronic affection due to some inexplicable national cutaneous traits or
inherent customs of living, a condition which certainly lacks many of
the essential elements of individuality.

The pathologic changes⁶ are such as are met with in chronic hyper-
plasias, such as eczema, and anatomically the process scarcely admits
of differentiation. The essential lesion—the papule—which, according
to investigation by several pathologists, has its origin in the rete, is of
a minute cystic character, and contains a clear fluid and some epithelia;
its upper covering is the entire corneous layer, which is un­disturbed,
except secondarily. It is thought to have some connection with the
sweat-gland duct. Apparently there are no changes in the peripheral
nerves. By some observers⁷ the papule is thought to be largely a

¹ Wigglesworth, Amer. Jour. Syph. and Derm., 1873, p. 1 (patient of American
parentage).

² Campbell, Arch. Derm., 1878, p. 119 (patient native born, but of German parent­
age).

³ Zeisler, Jour. Cutan. Dis., 1889, p. 408 (12 cases—only 1 of American parentage,
although several born in this country).

⁴ Taylor and Van Gieson, New York Med. Jour., 1891, vol. liii, p. 1; Dade, Jour.
Cutan. Dis., 1902, p. 569 (also a case in a child of foreign parentage).

⁵ J. C. White, “Prurigo,” Jour. Cutan. Dis., 1897, p. 2 (with many cited opinions
and literature references).

⁶ Van Gieson, in Taylor and van Gieson‘s paper, loc. cit., gives a good résumé of the
histology, with numerous illustrations and references; also Holder, Trans. Amer. Derm.
Assoc. for 1901.

⁷ Holder, “Prurigo, and the Papule with the Urticarial Basis,'’ Jour. Cutan. Dis.,
1911, p. 228, with brief review of the subject.

14

2IO

INFLAMMATIONS

result of traumatism—from the scratching and rubbing of a pruritic
skin.

Diagnosis.—A typical example of prurigo scarcely admits of
error: the poor general health, its early beginning, long duration, the
dry, harsh, hard, and thickened skin, especially over the extensor sur­
faces, the freedom of the flexures of the joints, the peculiar, scarcely ele­
vated papules, the intense itching, with the consequent excoriation, and
the enlarged inguinal glands, are characteristic. The milder cases possess
the same features, but much less marked, and closely resemble papular
eczema. It is to be noted that in neglected cases eczematous symptoms
are added; but treatment will soon remove these, and the character of
the true disease be disclosed. A careless examination might lead to a
confusion with a long-continued pediculosis or scabies.

Prognosis and Treatment—The severe cases are practically
hopeless as to permanent relief, although much can be done in every
case toward palliation. Under favorable circumstances and the insti­
tution of early treatment the milder cases admit of cure, but even in
these latter recurrences are often observed. The imported cases in
this country usually show, after a time, marked amelioration and even
complete disappearance—resulting from the better food and more com­
fortable and hygienic mode of living.

Both constitutional and local measures are required in the manage­
ment of the disease. The systemic treatment aims to put the patient in
a thoroughly healthy state, with attention to hygiene, and with usually
such remedies as cod-liver oil and iron, manganese, and a generous
dietary. Carbolic acid, pilocarpin (hypodermically administered), and
thyroid extract have their advocates; arsenic seems without influence.

The external treatment, which is of essential importance, consists
of frequent warm to hot plain or alkaline baths, tar-baths, baths of
potassium sulphid, followed by an oily application. A B-naphthol
ointment—in children, of 2 per cent, strength, and in adults, of 5 per
cent.—rubbing it in every night, is highly extolled by Kaposi, and is
the favorite method in Vienna; every second day a prolonged bath
in warm water with naphthol-sulphur soap is taken. The frequent
use of sapo viridis, or its tincture, with baths, is also valuable in older
subjects, followed by emollient ointments. Strong salicylic acid oint­
ments, from 20 to 60 grains (1.3 to 3.) to the ounce, are also useful
in some cases. In cases in which marked eczematous eruption has
been added, mild applications are at first demanded.

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