Pityriasis Pilaris

Devergie, who was the first to describe this rare dermatosis, states that in its most benign form it consists of a more or less localized eruption on the external aspects of the members, and especially the forearms and legs. The essential seat of the eruption is at the pilous orifices of the general surface, but not on the scalp. The only lesion is a minute papule, with a small adhering scale.

In more severe cases it may become generalized, with slight thickening of the skin about the follicle, forming a small, red pyramidal papule decked with a white scale. The skin between the papules is apparently unchanged. There is little or no pruritus, and it apparently causes but trifling inconvenience to the patient, except as it progresses from bad to worse.

It is exceedingly obstinate, and palliative and emollient treatment is our only resource.

When associated, as it may be, with pityriasis rubra, it presents a striking likeness to lichen, rubra and may possibly be in reality the same affection.


There is considerable discussion as to whether pityriasis is not a parasitic affection. Some observers claim to have discovered a special parasite in this affection, consisting of very minute spores, averaging a thousandth of a millimetre in diameter. The extreme smallness of the spores and their irregularity in size have induced M. Vidal to name the parasite Microsporon anomoron or dispar.

This is a point that has not been fully settled as yet, and I prefer to class the disease among the squamous inflammations until further light has been thrown upon the subject.

Sepia and Natr. ars. are the principal internal remedies for pityriasis pilaris.