KERATOSIS PILARIS

Synonyms.—Pityriasis pilaris; Lichen pilaris; Fr., Keratose pilaire; Xérodermie
pilaire (Besnier).

Definition.—Keratosis pilaris is a hypertrophic affection char­
acterized by the formation of pin-head-sized or slightly larger conic
epidermic elevations seated about the apertures of the hair-follicles,
and most commonly presenting on the outer anterolateral and pos-
terolateral aspects of the thighs and arms.

Symptoms.—In this disease conic, sometimes slightly acuminate
or flattened, papules, the size of a pin-head, and of a whitish, grayish,
or dark-gray color, and consisting of epithelial cells and sebaceous mat­
ter, are situated at the outlets of the hair-follicles, from which they pro­
ject. Not infrequently the lesions are somewhat larger, and quite
elevated; exceptionally the color is blackish. They are discrete, nu­
merous, do not form patches or distinct aggregations, but, although closely
set, are more or less evenly distributed over the affected regions. They
are usually located on the extensor and outer surfaces of the thighs and
arms, and sometimes also on the trunk, and in rare instances show a more
or less general distribution. On close inspection the papules are seen to
be pierced by a hair, which is either lanugo-like in character or broken
off at the apex of the papule, when it is seen as a dark point in the center
of the lesion, or is coiled within the papule. They are somewhat hard,
harsh, and dry, and the apex slightly scaly, and to the hand passed over
the part feel like the surface of a nutmeg-grater. If the accumulation
falls out or is rubbed or picked out, a small depression marks the site

¹ See prelimininary chapter on Treatment for references to trichloracetic acid.

538

HYPERTROPHIES

temporarily, occupying the opening of the hair-follicle. Sometimes
the enveloping basal follicular outlet is somewhat reddened and elevated,
and the papule then noted to be of a slightly inflammatory character.

The intervening skin between the papules is generally dry and
harsh to the touch, sometimes with a trifling furfuraceous scaliness.
On the neighboring regions it may, and usually does, present a per­
fectly healthy appearance, although not infrequently the skin over most
of the surface is also found harsh and dry, and suggestive of a mild
ichthyosis, which malady, in fact, occasionally may be associated. In
rare instances in a few of the lesions there may be an accidental pus­
tular capping. There are, indeed, considerable variations in extent
and development. In its milder forms it is not uncommon, and often
it is so slight as almost to escape notice. In the latter instances it bears
rough resemblance to goose-flesh. Quite often it is limited to the thighs
alone. In other cases the lesions are very pronounced and may be
distributed over a considerable part of the surface. It is rare, however,
to find the eruption on the flexor aspects. Its development is insidious
and slow, and occurs during the cool or cold season; warm weather gives
rise to free action of the sweat- and sebaceous glands, the skin is kept
soft, supple, and moist, and the dryness and epidermic papules cannot
readily be produced. Subjective symptoms are usually absent, although
occasionally moderate or even considerable itching is complained of.

Etiology and Pathology.—The affection is more common
during early adult life, although it may be met with at any age, except­
ing possibly earliest infancy. It is most frequently observed, moreover,
during the winter months, and usually in those who have naturally
rather dry skin and who are unaccustomed to frequent bathing. In
some individuals, however, there is a greater tendency to development
exhibited, and sometimes in spite of moderately frequent washing, so
that there is probably another etiologic element—doubtless a hereditary
predisposition to a dry skin. It has been considered by some observers
to occur much more frequently in those of a cachectic or scrofulous
tendency, but apparently it is just as common in those of vigorous and
robust nature. Those who naturally have somewhat active perspira­
tory secretion are rarely affected. Its greatest development is observed
in ichthyosis, of which disease it is a pathologic part.

Anatomically the malady essentially consists of a hyperkeratinization
of the upper part of the pilosebaceous follicular outlet, and the papular
elevation results from the formation of this superabundant or accumu­
lated epidermic horny mass, which projects beyond the orifice. To
this, in some instances, slight basal congestion is added secondarily, and
probably purely as the result of the irritation produced by this collection
or possibly for some unknown pathologic reason; and in occasional cases,
instead of such trifling basal congestion, there is distinct, though usually
extremely slight, inflammatory infiltration. In extreme instances of
these latter types there is some suggestion of the same pathologic process
as in pityriasis rubra pilaris, and it is not impossible that some of the
cases of keratosis pilaris occasionally referred to as of peculiar distribu­
tion and of excessive horny development, and otherwise anomalous,

KERATOSIS PILARIS

539

are on the border­line between these two maladies. It is probably in
such instances only that the superficial perifollicular cell-infiltration is
found (Crocker, Unna, Giovannini, and others). The congestive and
inflammatory elements, when present, give the lesions a somewhat
different aspect, and doubtless, chiefly based upon these factors, Brocq¹
divides the cases into several forms—keratosis pilaris alba, keratosis
pilaris rubra, and two intermediate divisions. In the extreme cases
of the latter—the inflammatory type—slight atrophy or scarring may
exceptionally result. Mibelli, Unna, and a few others do not consider
the lesion of this malady and the apparently similar one of ichthyosis as
pathologically identical. According to Giovannini,² Mibelli,³ and
Lemoine,⁴ there are also, at least in some cases, atrophic changes in the
sebaceous glands, which may, in fact, entirely disappear; the first named,
moreover, found atrophy of the hair-papilla.

Diagnosis.—The character of the eruption, its persistently dis­
crete lesions, with no attempt at grouping or to the formation of coal-
escent solid patches, and its common localization will serve to prevent
error. It is to be distinguished chiefly from goose-flesh (cutis anserina),
the miliary-papular syphiloderm, and lichen scrofulosus. In goose-flesh
the elevations, due to sudden chilling or excitement, are evanescent,
not rough, harsh, and scaly, and subside rapidly as suddenly as they came
upon the surface being warmed, being rarely present more than a few
minutes. The dull ham, brownish-red colored papules in the miliary-
papular syphilid have a more general distribution, are distinctly in­
filtrated, and therefore firmer to the touch, and tend to aggregation and
groups; the slight scaliness is a late phase. There will be found also
other symptoms of syphilis. In lichen scrofulosus—a rare disease—
the eruption is usually limited, and occurs in distinct, more or less rounded
groups or patches, and most commonly upon the trunk, especially the
abdomen, the extensor aspects of the extremities rarely being involved;
the lesions are firmer and less scaly. In pityriasis rubra pilaris the scaly
condition of the scalp and the horny thickening of the palms, as well as
the plaque and confluent tendency and distribution, are totally different
from the eruption of keratosis pilaris. It can scarcely be confused with
eczema or lichen planus, both itchy inflammatory diseases of different
character, behavior, and distribution.

Treatment.—The common clinical type yields readily, the con­
dition often being removed in the course of a few weeks, and wholly
as the result of external treatment. In some rare instances, more espe­
cially, however, the inflammatory type, the end is not so soon reached.
In such cases, particularly in ill-nourished individuals, cod-liver oil,
arsenic, and iron are sometimes to be advised. Rarely, however, are
more than external measures required, and these consist ordinarily of

¹ Brocq, “Notes pour servir a l‘histoire de la kératose pilaire,” Annales, 1890, pp.
25, 97, and 222 (a complete exposition and review of the subject with many references).

² Giovannini, “Contributione allo studio istologico della cheratosi pilare,” Lo Speri-
mentale, 1895, p. 661—abstract in Brit. Jour. Derm., 1896, p. 151.

³ Mibelli, “Zur Aetologie und die Varietätaten der Keratosen,” Monatshefte, 1897,
vol. xxiv, pp. 345 and 415 (with numerous references).

⁴ Lemoine, “De l‘ichthyose ansérine des scrofuleux,” Annales, 1882, p. 275.

540

HYPER TROPHIES

frequent local or general baths, plain warm baths, with the use of an
ordinary toilet soap or sapo viridis. In other cases the baths should
be alkaline, using for this purpose from 1 to 6 ounces (32.-192.) of sodium
carbonate, sodium borate, or sodium bicarbonate to about 30 gallons
(120. 1.) of water; in others, in addition to the baths, supplementary
applications of a mild salicylated ointment, from 10 to 30 grains (0.65-2.)
to the ounce (32.) of petrolatum or lard and lanolin, will be found nec­
essary. In fact, the management is practically the same as employed
in the milder cases of ichthyosis. In some individuals, however, fre­
quent bathing must be subsequently followed to prevent its recurrence.

Lichen Spinulosus.— Crocker describes¹ (under the name
lichen pilaris seu spinulosus) another somewhat similar malady in some
of its aspects, but which is slightly inflammatory, often patchy, and
occurs on almost any region. I draw largely from his description.
It may develop acutely or subacutely in crops, and consists of papules
about the size of a pin-head, red, conic, and containing in its center a
horny spine projecting about ¹/₁₆ of an inch; this epidermic plug can be
picked out, leaving a depression in the papule. After some duration
the papule loses its redness and becomes the color of the normal skin.
The papules are densely crowded into patches, often large and irregular
in outline, symmetrically distributed, sometimes in a few, sometimes
in many, regions. The favorite sites are the back of the neck, the but­
tocks, over the trochanters, the abdomen, the back of the thighs, the
popliteal spaces, and the extensor surfaces of the arms. The hands, feet,
face, and upper part of the chest are, according to Crocker‘s observations,
not attacked. There is a tendency, in cases in which the eruption is
not dense, to form roundish groups, with some scattered papules between.
The eruption comes out in crops, sometimes a patch appearing over night,
gradually increasing in extent for a week; after this the lesions grow
paler, but beyond this the eruption usually persists without change
more or less indefinitely. The cause is unknown. It occurs chiefly
in children, and in Crocker‘s experience more frequently in boys. In a
few instances it was associated with lichen planus and with lichen scrofu-
losus. It bears resemblance to keratosis pilaris and to pityriasis rubra
pilaris. Alkaline baths with friction, and in the inflammatory stage

¹ Crocker, Diseases of the Skin, third edit., p. 452; Adamson, “Lichen Pilaris, seu
Spinulosus,” Brit. Jour. Derm., Feb. and March, 1905 (with case illustration and histo-
logic cuts), has recently given a full account and review of the disease and the literature.
As examples of lichen spinulosus to be found in French literature, he quotes the follow­
ing: (1) possibly the acné cornée of Hardy; (2) certainly the acné cornée of Guibout
and of Leloir and Vidal; (3) the case of acné cornee en aires of Hallopeau, possibly
his 3 cases of acné cornée in adults; (4) Barbe‘s cases of kératose folliculaire (type de
Brooke); (5) Audry‘s cases of kératose pilaire engainante: and in Italy (6) Giovannini‘s
case of acne cornea. Histologically the lesions show that the pathologic process is essen­
tially a hyperkeratosis of the follicle; perifollicular inflammation is absent or, at any rate,
very little marked. Lewandowsky, Archiv, 1905, vol. lxxiii, p. 343 (with histologic
cuts), who describes a German case, believes it an inflammation of the follicle with a
secondary parakeratosis; Bowen, Jour. Cutan. Dis., 1906, p. 416 (report of a case;
youth aged nineteen). I have seen 2 cases in the past two years; before that date the
condition had never been under my observation; Beck, “Ueber keratosis spinulosa”
(Lichen spinulosus, Crocker), Dermatolog. Wochenschr., Nov. 30, 1912, lv, p. 1459,
clinical and histolog., with review and bibliography.

KERATOSIS F0LL1CULARIS

541

supplemented by a mild grease or oil; or, if sluggish, with weak tincture
of green soap, containing a dram (4.) of oil of cade to the ounce (32.),
prove successful. The constitutional treatment is according to indica­
tions: cod-liver oil, iron, and other tonic measures are most frequently
called for.

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