Conditions That Cause Hair Loss
Hair loss (alopecia) results from a broad spectrum of conditions that are best categorized into non-scarring and scarring alopecias, with non-scarring forms being far more common and further subdivided into diffuse, patterned, and focal patterns. 1, 2
Non-Scarring Alopecias
Diffuse Hair Loss
Telogen effluvium is a common self-limited condition triggered by physiological stress, medications, nutritional deficiencies, or systemic illness that causes diffuse shedding. 3, 1 This occurs when hair follicles prematurely enter the resting (telogen) phase.
Anagen effluvium results from drug-induced damage (particularly chemotherapy) that affects actively growing hair follicles, causing rapid hair loss that can mimic diffuse alopecia areata. 3
Patterned Hair Loss
Androgenetic alopecia (AGA) is the most common form of hair loss, affecting over 80 million people in the United States. 1 This genetic condition presents as progressive miniaturization of hair follicles in characteristic patterns—frontal and vertex thinning in men, and diffuse crown thinning with frontal hairline preservation in women. 1, 4
Focal Hair Loss
Alopecia areata is a chronic autoimmune inflammatory disease affecting hair follicles, presenting as well-demarcated patches of hair loss with characteristic "exclamation mark hairs" at the margins. 3 The condition can progress to alopecia totalis (complete scalp hair loss) or alopecia universalis (total body hair loss) in 14-25% of cases. 3
Trichotillomania is a psychiatric condition involving compulsive hair pulling that creates irregular patches of incomplete hair loss with firmly anchored broken hairs still in the growth phase. 3
Tinea capitis is a fungal scalp infection that causes patchy hair loss with scalp inflammation, though signs may be subtle. 3
Traction alopecia results from chronic tension on hair follicles from tight hairstyles, braiding, or hair extensions. 1
Scarring (Cicatricial) Alopecias
These conditions cause permanent destruction of hair follicles and require prompt diagnosis and treatment. 2, 5
Lichen planopilaris (LPP) is a lymphocyte-mediated inflammatory condition causing progressive scarring alopecia. 2, 5 The frontal fibrosing variant presents with characteristic frontotemporal hairline recession and eyebrow loss. 2
Discoid lupus erythematosus causes scarring patches with erythema, scaling, and follicular plugging, often associated with systemic lupus erythematosus. 3, 2, 5
Folliculitis decalvans is a neutrophil-associated scarring alopecia with pustules and crusting. 2
Pseudopelade presents as smooth, atrophic patches of scarring alopecia without significant inflammation. 5
Systemic Diseases Causing Hair Loss
Autoimmune diseases including systemic lupus erythematosus and thyroid disorders (both hypothyroidism and hyperthyroidism) are associated with hair loss. 3, 6
Endocrine disorders such as diabetes mellitus and hormonal imbalances can trigger hair loss. 6
Nutritional deficiencies, though iron deficiency's role in alopecia areata remains controversial with conflicting evidence. 3
Secondary syphilis can present with patchy "moth-eaten" alopecia. 3
Critical Diagnostic Considerations
When evaluating hair loss, distinguish between scarring and non-scarring forms immediately, as scarring alopecias require urgent intervention to prevent permanent follicle destruction. 2
Dermoscopy is fundamental for all hair diseases and can identify characteristic features: yellow dots in alopecia areata, follicular plugging in lupus, and absence of follicular openings in scarring alopecias. 3, 2
Scalp biopsy is strongly suggested in cicatricial alopecia and doubtful cases to establish definitive diagnosis. 2 When diagnosis is uncertain, appropriate testing includes fungal culture, skin biopsy, lupus serology, or syphilis serology. 3
Psychosocial Impact
Hair loss carries substantial psychological burden beyond cosmetic concerns, with patients experiencing anxiety, depression, decreased work productivity, and significantly reduced quality of life—particularly affecting women for whom hair represents femininity and attractiveness. 3, 6 The mental burden often exceeds the physical burden, with patients reporting feeling self-conscious, conspicuous, and behaving in defensive or retreating manners. 3, 7