What is the differential diagnosis, appropriate work‑up, and management for progressive hair loss in a young woman?

Progressive Hair Loss in Young Women

Differential Diagnosis

The most common causes of progressive hair loss in young women are androgenetic alopecia (female pattern hair loss), telogen effluvium, and alopecia areata, each distinguished by specific clinical patterns on scalp examination. 1

Pattern Recognition on Examination

• Androgenetic alopecia presents with diffuse thinning over the central/parietal scalp while the frontal hairline remains intact—this is the classic "Christmas tree pattern" with wider thinning frontally. 1, 2
• Alopecia areata shows discrete round patches with pathognomonic "exclamation mark hairs" (short broken hairs 2-3mm long at patch margins) visible on dermoscopy. 1, 3
• Telogen effluvium causes diffuse shedding across the entire scalp without the central predominance seen in androgenetic alopecia, typically triggered 2-3 months after a stressor (illness, surgery, rapid weight loss, emotional stress). 1, 4
• Tinea capitis presents with scalp inflammation, scaling, and broken hairs—fungal culture is mandatory before treatment. 1, 4
• Trichotillomania shows incomplete hair loss with firmly anchored broken hairs that remain in anagen phase, distinguished from alopecia areata where hairs pull out easily. 1, 3

Red Flags Requiring Urgent Work-Up

• Scalp inflammation or scarring suggests scarring alopecia (frontal fibrosing alopecia, lupus) or tinea capitis—these require immediate biopsy or fungal culture. 1, 5
• Signs of androgen excess (severe acne, hirsutism, irregular menses, virilization) may indicate PCOS, adrenal hyperplasia, or rarely androgen-secreting tumors. 4, 6

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Diagnostic Work-Up

Essential History Elements

• Duration and pattern: Onset <1 year suggests better prognosis in alopecia areata (34-50% spontaneous remission); gradual onset after puberty suggests androgenetic alopecia. 1, 3
• Medication review: Chemotherapy causes anagen effluvium; anticoagulants, beta-blockers, and retinoids cause telogen effluvium. 1, 3
• Triggers for telogen effluvium: Recent illness, surgery, childbirth, crash dieting, severe emotional stress within past 2-4 months. 1, 4
• Family history: 20% of alopecia areata patients have affected relatives; androgenetic alopecia shows polygenic inheritance. 3, 4
• Menstrual history and signs of hyperandrogenism: Irregular periods, acne, hirsutism suggest PCOS or other endocrine disorder. 3, 4

Physical Examination Specifics

• Dermoscopy is the single most valuable diagnostic tool to differentiate causes: yellow dots and exclamation mark hairs confirm alopecia areata; hair diameter diversity >20% indicates androgenetic alopecia. 1, 4
• Check for nail changes (pitting, ridging)—present in 10% of alopecia areata patients and indicates poorer prognosis. 3, 4
• Examine scalp for inflammation, scaling, or scarring—their presence excludes androgenetic alopecia and alopecia areata. 1, 3
• Perform hair pull test: >6 hairs pulled from 60-hair bundle indicates active telogen effluvium or active alopecia areata at patch margins. 1, 3

Laboratory Testing Algorithm

For clinically obvious alopecia areata (discrete patches with exclamation mark hairs on dermoscopy), no laboratory testing is required. 1, 3

For androgenetic alopecia without signs of hyperandrogenism, no hormonal testing is needed—proceed directly to treatment with topical minoxidil 2%. 1, 6

Targeted Testing When Indicated:

• Check TSH and free T4 in all cases of diffuse hair loss, as thyroid disease is a common reversible cause. 1, 4
• Serum ferritin should be checked if iron deficiency is suspected; optimal level for hair growth is ≥60 ng/mL, not just >15 ng/mL. 1, 4
• Vitamin D level should be measured, as 70% of alopecia areata patients are deficient (<20 ng/mL) versus 25% of controls, and lower levels correlate with disease severity. 4, 5
• Serum zinc may be checked in resistant alopecia areata >6 months duration. 1, 4
• Total testosterone, free testosterone, and SHBG should only be checked if signs of androgen excess are present (acne, hirsutism, irregular periods). 1, 4
• Fungal culture is mandatory only when scalp inflammation or scaling suggests tinea capitis. 1, 3
• Scalp biopsy is reserved for uncertain diagnosis, suspected scarring alopecia, or when dermoscopy is inconclusive. 1, 4

Common Pitfall to Avoid:

Do not order extensive autoimmune panels for straightforward alopecia areata—the modest increase in autoimmune disease prevalence does not justify routine screening. 1, 3

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Management

Androgenetic Alopecia (Female Pattern Hair Loss)

Topical minoxidil 2% solution applied 1 mL twice daily is the only FDA-approved first-line treatment for women with androgenetic alopecia; it arrests progression rather than stimulates regrowth and requires continuous use. 1, 2

• Treatment must continue indefinitely—stopping results in loss of any gained benefit within 3-6 months. 1, 2
• Visible improvement requires minimum 6-12 months of consistent use. 2, 5
• If signs of hyperandrogenism are present (PCOS, elevated androgens), add oral antiandrogen therapy: spironolactone 100-200 mg daily or cyproterone acetate 50-100 mg days 1-10 of menstrual cycle with ethinylestradiol contraceptive. 7, 5
• Platelet-rich plasma (PRP) injections show promise as adjunctive therapy: 3-5 sessions at 1-month intervals, then maintenance every 6 months. 1, 5

Alopecia Areata

Limited Patchy Disease (≤5 patches, each ≤3 cm):

Watchful waiting with reassurance is the recommended first-line approach, as 34-50% of patients achieve spontaneous regrowth within one year without treatment. 1, 3

• Counsel patients that regrowth cannot be expected within 3 months of any individual patch development. 1, 3
• If treatment is desired, intralesional triamcinolone acetonide 5-10 mg/mL (0.05-0.1 mL per injection site) administered monthly achieves regrowth in 62% of patients (Strength of recommendation B, Quality of evidence III). 1, 3

Extensive Disease (>50% scalp involvement):

• Contact immunotherapy with diphenylcyclopropenone (DPCP) is the best-documented treatment but achieves response in <50% of patients and requires multiple hospital visits over months (Strength of recommendation B, Quality of evidence II-ii). 1, 3
• Wigs provide immediate cosmetic benefit and are often the most practical solution for extensive, longstanding disease. 1, 3

Treatments to Avoid:

• Do not use potent topical corticosteroids for alopecia areata—lack of convincing efficacy evidence. 1
• Do not prescribe systemic corticosteroids or PUVA—potentially serious side effects with inadequate efficacy evidence. 1
• Oral zinc and isoprinosine are ineffective in controlled trials. 1

Telogen Effluvium

Identify and remove the precipitating trigger (stress, nutritional deficiency, illness)—80% of cases with duration <1 year resolve spontaneously once the trigger is addressed. 1, 4

• Supplement iron if ferritin <60 ng/mL, vitamin D if <20 ng/mL, and zinc if deficient. 1, 4
• Reassure patients that shedding typically stops 3-6 months after trigger removal and full regrowth occurs by 6-12 months. 1, 4

Tinea Capitis

Systemic oral antifungal therapy is required—topical treatment alone is insufficient. 1, 4

• Obtain fungal culture before initiating treatment to guide antifungal selection. 1, 3

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Psychological Support

Hair loss can cause profound psychological distress—patients who become withdrawn, experience low self-esteem, or encounter work/social difficulties should be referred to mental health services. 1, 3

• The psychological impact must be addressed as actively as the physical condition. 1, 3
• Cosmetic camouflage (hairpieces, extensions, scalp micropigmentation) provides immediate benefit while awaiting treatment response. 1, 8

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Prognosis Indicators

Poor Prognosis in Alopecia Areata:

• Childhood onset (worse than adult onset). 3, 4
• Ophiasis pattern (scalp margin involvement). 4
• Nail changes present. 3, 4
• Duration >1 year. 1, 3
• Family history of alopecia areata. 3, 4
• Associated atopic disease (eczema, asthma). 3

Good Prognosis:

• Limited patches (<5 patches, each <3 cm). 1, 3
• Duration <1 year. 1, 3
• Adult onset. 3, 4