A patient presents with hair loss; what are the differential diagnoses and what initial history, physical examination, laboratory tests, and first-line management should be undertaken?

Hair Loss: Differential Diagnosis and Initial Management

For a patient presenting with hair loss, begin by examining the scalp for patchy versus diffuse loss and looking for exclamation-mark hairs on dermoscopy, which are pathognomonic for alopecia areata—the most common autoimmune cause requiring no routine laboratory testing when clinically evident. 1

Initial History: Key Questions to Ask

• Duration of hair loss: Onset <1 year suggests better prognosis with 34-50% spontaneous remission in alopecia areata, while chronic loss >1 year indicates different etiologies 1

• Pattern recognition: Ask whether hair is falling out in discrete patches (suggests alopecia areata or tinea capitis) versus diffuse thinning across the entire scalp (suggests telogen effluvium or androgenetic alopecia) 1, 2

• Recent stressors: Specifically inquire about illness, surgery, childbirth, severe emotional stress, rapid weight loss within the past 3-6 months—all triggers for telogen effluvium 2

• Medication history: Document chemotherapy (causes anagen effluvium), anticoagulants, beta-blockers, and any new medications started in the past 6 months 1

• Hair-care practices: Ask about tight hairstyles (braids, ponytails, extensions) that cause traction alopecia, and compulsive hair-pulling behaviors suggesting trichotillomania 1, 3

• Family history: 20% of alopecia areata patients have affected family members; also ask about early-onset baldness in relatives (androgenetic alopecia) 1, 3

• Associated symptoms: Screen for signs of androgen excess (acne, hirsutism, irregular periods), thyroid dysfunction (weight changes, fatigue), and autoimmune diseases (joint pain, photosensitivity) 1, 2

Physical Examination: Specific Features to Identify

Scalp Examination

• Exclamation-mark hairs (short broken hairs 2-3mm long at patch margins) are pathognomonic for alopecia areata and can be identified with dermoscopy 1, 3

• Yellow dots on dermoscopy indicate active alopecia areata and are highly specific for this diagnosis 1, 2

• Scalp inflammation or scaling suggests tinea capitis or early scarring alopecia rather than alopecia areata or androgenetic alopecia 1

• Pattern of loss: Diffuse central scalp thinning with preserved frontal hairline indicates androgenetic alopecia in women; temporal-frontal recession indicates androgenetic alopecia in men 1, 4

• Firmly anchored broken hairs that resist gentle pulling distinguish trichotillomania from alopecia areata (where hairs pull out easily at active margins) 1, 2

Additional Examination Findings

• Nail changes (pitting, ridging, dystrophy) occur in 10% of alopecia areata patients and predict poorer prognosis 2, 3

• Signs of androgen excess: Examine for acne, hirsutism, and perform pelvic examination in women with irregular periods to screen for polycystic ovary syndrome 1

• Thyroid examination: Palpate for goiter or nodules, as thyroid disease commonly associates with alopecia areata 2, 3

Laboratory Testing: Targeted Approach

Laboratory testing is unnecessary in most cases when alopecia areata is clinically evident with characteristic exclamation-mark hairs and patchy loss. 1, 3

When to Order Laboratory Tests

Order targeted tests only when: 1, 2

• Diagnosis is uncertain or presentation is atypical
• Diffuse hair loss without clear pattern
• Signs of systemic disease are present
• Scalp inflammation or scaling is noted

Specific Tests Based on Clinical Suspicion

• Fungal culture: Order only if scalp inflammation or scaling suggests tinea capitis 1, 2

• Serum ferritin: Check if iron deficiency suspected; optimal level ≥60 ng/mL needed for hair growth 1, 3

• TSH and free T4: Check for thyroid disease, which commonly causes hair loss and associates with alopecia areata 1, 3

• Vitamin D level: 70% of alopecia areata patients have levels <20 ng/mL versus 25% of controls; lower levels correlate with disease severity 1, 2

• Serum zinc: Tends to be lower in alopecia areata patients, particularly those with resistant disease >6 months 2

• Total testosterone, free testosterone, SHBG: Order only if signs of androgen excess present (acne, hirsutism, irregular periods) 1

• Lupus serology: Order only if systemic features such as joint pain, photosensitivity, or facial rash are present 2

• Syphilis serology: Order only in individuals with relevant risk factors 2

• Scalp biopsy: Reserve for uncertain diagnosis, suspected scarring alopecia, or when dermoscopy is inconclusive 1, 2

Common Pitfalls to Avoid

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

• Do not confuse trichotillomania with alopecia areata: Trichotillomania shows firmly anchored broken hairs in anagen phase, whereas alopecia areata displays exclamation-mark hairs that pull out easily 1, 2

• Do not overlook the psychological impact: Hair loss causes considerable psychological distress; patients with withdrawal, low self-esteem, or work/social difficulties require mental health referral 1, 5

• Do not promise cure or permanent regrowth in alopecia areata—the disease course is unpredictable and relapses are common even with treatment 3

First-Line Management by Diagnosis

Alopecia Areata (Limited Patchy Disease)

Watchful waiting with reassurance is the recommended first-line approach for limited patchy alopecia areata (<5 patches, each <3 cm), as 34-50% of patients recover within one year without treatment. 1, 3

• If treatment is desired, intralesional triamcinolone acetonide 5-10 mg/mL (0.05-0.1 mL per injection) administered monthly achieves regrowth in 62% of patients (Strength of recommendation B, Quality of evidence III) 1

• Counsel patients that regrowth cannot be expected within 3 months of any individual patch development 1, 3

• No treatment alters the long-term natural history of alopecia areata, though some interventions induce temporary regrowth 1

Alopecia Areata (Extensive Disease >50% Scalp)

• Contact immunotherapy with diphenylcyclopropenone (DPCP) is the best-documented treatment, achieving response in <50% of appropriately selected patients; requires multiple clinic visits over months (Strength of recommendation B, Quality of evidence II-ii) 1

• Wigs provide immediate cosmetic benefit and are often the most practical solution for extensive, longstanding disease 1

Androgenetic Alopecia

• Topical minoxidil 2% solution twice daily is first-line treatment for women; arrests progression rather than stimulates regrowth 1, 4

• Oral finasteride 1 mg daily plus topical minoxidil 5% twice daily is first-line combination therapy for men; treatment must be continuous to maintain results 1

Telogen Effluvium

• Remove the precipitating trigger (stress, nutritional deficiency, illness); spontaneous remission occurs in up to 80% of cases with short duration (<1 year) 1

• Address any identified nutritional deficiencies (iron, vitamin D, zinc) 1, 2

Tinea Capitis

• Systemic oral antifungal therapy is required; fungal culture must be obtained before initiating treatment 1, 3

Trichotillomania

• Treatment focuses on the underlying psychiatric condition; requires psychological counseling rather than immunologic treatment 3

When to Refer to Dermatology

• Diagnosis remains uncertain despite clinical and dermoscopic evaluation 1
• Extensive alopecia areata requiring contact immunotherapy 1
• Suspected scarring alopecia or treatment-resistant cases 1
• Scalp biopsy needed for definitive diagnosis 1, 2