Age-related hair loss is a very slow, gradual thinning, whereas diffuse AA is a more rapid and profound shedding process.
Anagen effluvium is an acute, massive shedding of growing hairs immediately following a major insult like chemotherapy, a much more dramatic event than diffuse AA.
FPHL is characterized by hair miniaturization and a widening of the central part, while diffuse AA is a more uniform thinning without this classic pattern.
Hair loss from hypothyroidism is a chronic, slow thinning associated with other systemic signs, unlike the more acute process of diffuse AA.
This is a chronic, diffuse hair thinning that responds to iron supplementation and is diagnosed by low ferritin levels.
This is a scarring alopecia, distinguished by perifollicular erythema and scale, and permanent loss of follicular openings.
Secondary syphilis can cause a diffuse, "moth-eaten" pattern of hair loss, which is patchier and more irregular than the uniform thinning of diffuse AA.
This is the most difficult differential; diffuse AA may be suggested by a more profound and persistent loss, presence of exclamation point hairs, and a positive hair pull test with dystrophic hairs, not just club hairs.
This is distinguished by a history of tight hairstyles and hair loss localized to the areas of maximum tension, such as the frontal hairline.
