(Pityriasis pilaris; Lichen pilaris)
Definition – A hypertrophic affection characterized by pin-head-sized, conical epidermal elevations seated at or about the mouths of the hair-follicles.
Symptoms – These convex, pin-head-sized or slightly larger papules vary in color from that of the normal skin to a greenish or blackish hue due to deposits of dirt; very rarely having a reddish tinge. The papules may be pierced centrally by a hair but more often the hair is broken off or imposed within. The depressed orifice of the follicle may be seen if the scale of the papule be removed, while the intervening or adjacent skin is usually dry or scaly and normal in color. this condition occurs symmetrically on the extensor and outer surfaces of the arms and thighs but occasionally may be found upon the trunk and elsewhere. If the papules are aggregated and numerous, the affected surface will feel like a nutmeg-grater to the touch. Sometimes there are so few lesions as to be scarcely noticeable. Resolved lesions in well-marked cases will show punctate scars at the seat of the old papules. The disease runs a chronic course but fortunately subjective sensations are few if any.
Etiology and Pathology. – This condition is most common before the twenty-fifth year and more marked in cold weather. It is usually found in those who have an abnormally dry skin or in those who are unaccustomed to frequent bathing. It is just as common in the vigorous and robust as in those who are cachectic. Some authorities consider it a physiological excess rather than a pathological development. Microscopically there is an excessive cornification of the epithelia of the outer portion of the pilosebaceous duct. This, forming a papular-like mass, closes the orifice of the hair-follicle. When the pressure is sufficient the superficial blood vessels become congested producing the redness sometimes seen. Scarring is due to atrophy of the hair and sebaceous structures or from secondary pustular inflammation.
Diagnosis – Cutis anserina or “gooseflesh” is temporary, never persistent or chronic. Lichen ruber is widespread, shows lesions upon the scalp and dorsal surfaces of the fingers and usually presents a seborrheic scaling. The small papular syphilids are generally distributed, tend to group, are deeper seated with little scaling and are associated with pustules or other manifestations of the general disease.
Prognosis and Treatment. – Most cases of this disease can be cured by simple treatment. The inflammatory type, however, is more persistent. It may be necessary at the onset of treatment to suggest a hot salt water bath twice weekly, followed by a thorough application of some simple oil or fat. Radiant- heat, alkaline or vapor baths or soft-soap inunctions followed by some simple fat or a very weak salicylic acid ointment may be applied. For the average chronic case a daily cold fresh or salt water bath followed by friction with a rough coarse towel and an occasional inunction of fat is the best treatment if it can be continued for months. Internal tonic treatment with cod-liver oil or one of the milder iron preparations may be indicated as well as a carefully prescribed general remedy, such as Arsenicum alb., Calcarea carb., Nat. mur., Petrol., and Staphysagria