In a 27‑year‑old woman taking amitriptyline, rizatriptan, and topical tretinoin who has a solitary well‑defined alopecic patch on the lateral scalp, what is the most likely diagnosis and recommended management?

Alopecia Areata: Diagnosis and Management

Most Likely Diagnosis

This is almost certainly alopecia areata, an autoimmune condition causing patchy, non-scarring hair loss that affects approximately 2% of the population. 1

Clinical Confirmation

Before initiating treatment, examine the scalp for these pathognomonic features:

• Exclamation mark hairs (short broken hairs around the patch margins) – these are diagnostic for alopecia areata 2, 3
• Yellow dots visible on dermoscopy, which is the single most useful non-invasive diagnostic tool 2
• Normal-appearing skin within the bald patch – no scaling, inflammation, or scarring should be present 3
• Positive hair pull test at patch margins indicates active, expanding disease 3

Medication Review

None of her current medications are likely culprits:

• Amitriptyline: Tricyclic antidepressants rarely cause hair loss, with only isolated case reports in the literature 4
• Rizatriptan: Not associated with alopecia
• Tretinoin: Topical retinoids are not linked to hair loss (unlike systemic retinoids which can cause telogen effluvium) 5

Recommended Management Algorithm

Step 1: Initial Treatment Choice

For a solitary, well-defined patch, intralesional corticosteroid injections are the first-line treatment with the strongest evidence (Strength of recommendation B, Quality of evidence III). 1, 3

Specific protocol:

• Use triamcinolone acetonide 5–10 mg/mL 1
• Inject just beneath the dermis in the upper subcutis 1
• Each 0.05–0.1 mL injection produces approximately 0.5 cm diameter of hair regrowth 1
• Repeat monthly injections 1
• Success rate: 62% achieve full regrowth, with better response in patients with fewer than five patches <3 cm diameter 1

Step 2: Alternative if Injections Declined

If the patient cannot tolerate injections, topical clobetasol propionate 0.05% foam is an alternative, though less effective:

• Apply to affected area daily 1
• Evidence shows 7 of 34 patients achieved ≥50% regrowth after 12 weeks 1
• Common pitfall: Folliculitis is a frequent side effect 1

Step 3: Observation Option

Reassurance with observation is a legitimate alternative, particularly given:

• Spontaneous remission occurs in up to 80% of patients with limited patchy hair loss of short duration (<1 year) 1
• 34-50% recover within one year without treatment 2, 3
• Hair regrowth cannot be expected within 3 months of patch development 1

Prognostic Factors

Favorable indicators in this case:

• Single patch (limited disease) 3
• Young age without childhood onset 3
• Lateral scalp location (not ophiasis pattern) 2

Poor prognosis indicators to watch for:

• Ophiasis pattern (scalp margin involvement) 2
• Family history of alopecia areata 2
• Associated autoimmune diseases 2

Laboratory Testing

Investigations are unnecessary in most cases when the diagnosis is clinically evident 2. However, consider testing if:

• Vitamin D level: 70% of alopecia areata patients are deficient (<20 ng/mL) versus 25% of controls, with inverse correlation to disease severity 2
• TSH: To screen for associated thyroid disease, present in approximately 20% of alopecia areata patients 2
• Fungal culture: Only if any scaling or inflammation is present to exclude tinea capitis 2, 3

Critical Counseling Points

Warn the patient about:

• No treatment alters the long-term course of the disease 1
• High relapse rates even after successful treatment 1
• Treatment effects last approximately 9 months with intralesional steroids 1
• Psychological impact: Alopecia areata causes considerable psychological and social disability; assess for anxiety and depression 2

Common Pitfalls to Avoid

• Do not order excessive laboratory tests when the diagnosis is clinically evident 2
• Do not promise permanent cure – treatments induce hair growth but don't alter disease course 1
• Do not overlook dermoscopy – it provides valuable diagnostic information non-invasively 2
• Do not assume medication causation without considering the high prevalence of alopecia areata (2% of population) 1, 2