What is the usual course of comedo?
Chronic. The lesions may persist indefinitely or the condition may be somewhat variable. In many instances, either as a result of pressure or in consequence of chemical change in the sebaceous plugs or of the addition of a microbic factor, inflammation is excited and acne results. The two conditions are, in fact, usually associated.
Fig. 8.
Demodex Folliculorum, X 300. Ventral surface. (After Simon).
To what may comedo often be ascribed?
To disorders of digestion, constipation, chlorosis, menstrual disturbance, lack of tone in the muscular fibres of the skin, the infrequent use of soap, and working in a dirty or dusty atmosphere. A small parasite (demodex folliculorum, acarus folliculorum) is sometimes found in the sebaceous mass, but its presence is without etiological significance, as it is also found in healthy follicles. A microbacillus has been found by several observers, and credited with etiological influence.
What is the pathology of comedo?
The sebaceous ducts or glands, or both, become blocked up with retained secretion and epithelial cells. The dark points which usually mark the lesions are probably due to accumulation of dirt, but may, as some writers maintain, be due to the presence of pigment-granules resulting from chemical change in the sebaceous matter.
Is there any difficulty in the diagnosis of comedo?