ing. There
are no constitutional symptoms.

#What is the etiology of lichen planus?#

In some cases the disease is distinctly neurotic in character, in others
no cause can be assigned. It is more especially met with at middle age,
and among the wealthier, professional, and luxurious classes.

Pathologically the first change noted in the epidermis is thought to be
an acanthosis, followed by epithelial atrophy, and a hyperkeratosis,
intercellular edema, and colloid degeneration of the prickle cells.

#Does the disease bear any resemblance to the miliary papular syphilide,
psoriasis, and papular eczema?#

In some instances it does, but the irregular and angular outline, the
slightly-umbilicated, flattened, smooth or scaly summits, and the
dull-red or violaceous color, the history and course, of lichen planus,
will serve to differentiate.

#State the prognosis.#

Under proper management the eruption, although often obstinate, yields
to treatment.

#What treatment would you prescribe in lichen planus?#

A general tonic plan of medication is indicated in most cases, with such
remedies as iron, quinine, nux vomica, and cod-liver oil and other
nutrients. In many instances arsenic exerts a special influence, and
should always be tried. Mercurials in moderate dosage have also a
favorable action in most cases. Locally, antipruritic and stimulating
applications, such as are used in the treatment of eczema, are to be
employed, alkaline baths and tarry applications deserving special
mention. Liquor carbonis detergens, applied weakened with several parts
water, is a valuable application. In some cases, particularly if the
disease is limited, external applications alone often suffice to bring
about a cure.

#Pityriasis Rubra Pilaris.#
(_Synonyms:_ Lichen Ruber; Lichen Ruber Acuminatus.)

#Describe pityriasis rubra pilaris.#

Pityriasis rubra pilaris is an extremely rare disease, usually of a
mildly inflammatory nature, characterized by grayish, pale-red or
reddish-brown follicular papules with somewhat hard or horny centres;
discrete and confluent, and covering a part or the entire surface. The
skin is harsh, dry and rough, feeling to the touch somewhat like the
surface of a nutmeg-grater or a coarse file. More or less scaliness is
usually present in the confluent patches and on the palms and soles; in
these latter regions the papules are rarely seen. The duration of the
dise