This patient's irregular, patchy hair loss, with areas of uneven hair and the absence of other findings, is most consistent with a diagnosis of trichotillomania, a behavioral disorder characterized by compulsive hair pulling.  Commonly affected sites include the scalp, eyebrows, and eyelids, with presentation of asymmetric, irregular areas of hair loss and/or absent eyebrows (eg, sparse eyebrows in this patient) and eyelashes.  Examination shows hairs of different lengths due to traumatic breakage at various points.  Erythema (characteristic of tinea capitis) and total hair loss (as seen in alopecia areata) are not present.

Hair pulling may be an automatic behavior (without full awareness) or preceded by tension followed by relief.  The prevalence of trichotillomania is estimated to be 1%-2% and is much more common in children and adolescent girls.  Because patients with trichotillomania feel out of control and embarrassed, they may avoid work, school, or public places and try to hide the hair loss (eg, wearing hats, wigs).  Patients who also ingest hair (trichophagia) may develop trichobezoars that can lead to abdominal pain and bowel obstruction.

(Choice A)  In alopecia areata, patches are circular, smooth, and completely devoid of hair, whereas in trichotillomania, patches are irregular, typically with broken hairs of varying lengths.

(Choice B)  Androgenetic alopecia in females (also known as female-pattern hair loss) occurs in adult women and is characterized by progressive hair thinning at the vertex and frontal hairline.

(Choice C)  Discoid lupus erythematosus, the most common form of chronic, cutaneous lupus erythematosus, is characterized by discrete, erythematous, and scaling plaques.

(Choice D)  Telogen effluvium is characterized by diffuse thinning of the hair rather than discrete patches of hair loss.  It results from premature shedding and is often triggered by stress (eg, major illness or surgery, malnutrition, emotional trauma).

(Choice E)  Tinea capitis is a fungal infection of the scalp and most commonly seen in children.  It presents with scaly, erythematous patches and alopecia, with black dots representing broken hairs within follicles.

(Choice F)  Traction alopecia is a type of hair loss resulting from prolonged tension on the hair due to hairstyles that stretch the hair (eg, braiding).  It would not explain this patient's sparse eyebrows, and hair loss in the frontal and temporal scalp is most common.

Educational objective:
Trichotillomania is a behavioral disorder characterized by recurrent hair pulling.  It results in irregular patches of hair loss with broken hair shafts of differing lengths.