Diseases Causing Alopecia and Scaling

Alopecic skin diseases without scaling:
Telogen effluvium (TE) is a syndrome of hair loss during the telogen or resting phase of the hair follicle. With TE, a stressful circumstance (e.g., fever, shock, severe illness, surgery, anesthesia) causes premature cessation of growth of many anagen hair follicles and synchronizes hair follicles in catagen (transition phase of the hair follicle) followed by telogen. Within 1-3 months after the insult, a large number of telogen hairs are shed as a new wave of hair follicle activity begins, leading to areas of both widespread and patchy alopecia.
Anagen effluvium (AE) is a syndrome of hair loss during the anagen or growth phase of the hair follicle. In contrast to TE, AE is generally caused by a severe infectious or metabolic disease or exposure to certain chemicals (e.g., antimitotic agents) that interferes with the anagen phase of the hair follicle and results in abnormalities of the hair follicle and hair shaft. Alopecia is usually abrupt and occurs within a few days of the insult. […]