How can severe alopecia with over 50% hair loss be differentiated from severe telogen effluvium?

Distinguishing Severe Alopecia (>50% Hair Loss) from Severe Telogen Effluvium

Severe alopecia with >50% hair loss can be differentiated from severe telogen effluvium through specific clinical features, trichoscopy findings, and hair pull test results, with trichoscopy showing hair shaft diameter variation and miniaturization in alopecia but uniform hair shafts in telogen effluvium. 1

Key Diagnostic Features

Clinical Presentation Differences

• Telogen Effluvium:

  • Diffuse shedding across the entire scalp
  • Clear triggering event 1-3 months before onset (childbirth, surgery, severe illness, sudden weight loss, emotional stress) 1, 2
  • Typically self-limited when trigger is removed 3
  • Often accompanied by trichodynia (scalp pain) 2
  • Hair regrowth visible at the hairline as short "baby hairs"

• Severe Alopecia (>50% hair loss):

  • May present as androgenetic alopecia, alopecia areata, or chemotherapy-induced alopecia
  • Pattern varies by type: diffuse thinning on crown (androgenetic), patchy loss (alopecia areata), or complete scalp loss (chemotherapy-induced) 4, 1
  • No clear triggering event in androgenetic alopecia
  • Chemotherapy-induced alopecia starts 1-3 weeks after treatment initiation 4

Diagnostic Tests

Hair Pull Test

• Telogen Effluvium: Strongly positive with >6 hairs easily extracted, with white bulbs visible at the root end 1
• Alopecia Areata: May be negative or weakly positive at margins of patches
• Androgenetic Alopecia: Weakly positive or negative in established cases

Trichoscopy Findings

• Telogen Effluvium:

  • Uniform hair shaft diameter
  • Increased proportion of telogen hairs (>20%)
  • Empty follicles
  • Absence of miniaturization

• Androgenetic Alopecia:

  • Hair shaft diameter variation >20%
  • Miniaturized hairs
  • Increased proportion of vellus hairs
  • Peripilar signs (brown halo)

• Alopecia Areata:

  • Exclamation mark hairs
  • Black dots
  • Yellow dots
  • Broken hairs

Laboratory Testing

For both conditions, rule out underlying causes with:

• Complete blood count
• Ferritin (iron deficiency is common in telogen effluvium) 1
• Thyroid function tests (TSH, free T4)
• Vitamin D 25OH levels
• Zinc levels 1

Timing and Progression

• Telogen Effluvium:

  • Acute onset 2-3 months after triggering event
  • Self-limiting, typically resolves within 6-9 months if trigger is removed
  • May become chronic if trigger persists beyond 6 months

• Chemotherapy-Induced Alopecia:

  • Rapid onset (1-3 weeks after treatment)
  • Severity depends on type, dose, and administration method
  • Hair regrowth begins 2-3 months after completion of chemotherapy 4

• Androgenetic Alopecia:

  • Gradual, progressive thinning
  • No spontaneous resolution without treatment
  • Endocrine therapy-induced alopecia develops between 6-18 months after therapy initiation 4

Scalp Biopsy Findings

When clinical diagnosis remains unclear, a 4mm punch biopsy can provide definitive differentiation:

• Telogen Effluvium:

  • Normal total hair count
  • Increased telogen:anagen ratio (>20% telogen hairs)
  • No follicular miniaturization
  • No inflammation

• Androgenetic Alopecia:

  • Miniaturization of follicles
  • Decreased anagen:telogen ratio
  • Terminal-to-vellus hair ratio <4:1

• Alopecia Areata:

  • Peribulbar lymphocytic infiltrate ("swarm of bees")
  • Increased catagen/telogen hairs

Common Pitfalls and Caveats

1. Mixed conditions: Telogen effluvium can unmask or exacerbate underlying androgenetic alopecia, creating a mixed clinical picture 1

2. Delayed diagnosis: The 2-3 month lag between trigger and hair loss in telogen effluvium often leads to missed associations with the causative event 2

3. Medication-induced telogen effluvium: Can be mistaken for other forms of alopecia; requires careful medication history including retinoids, antifungals, and psychotropic medications 5

4. Psychological impact: Both conditions significantly impact quality of life and may cause anxiety and depression, requiring psychological support alongside treatment 1, 6

5. Chronic telogen effluvium: Can be mistaken for androgenetic alopecia when it persists beyond 6 months 2

By systematically evaluating these clinical features, diagnostic tests, and considering the timeline of hair loss, clinicians can effectively differentiate between severe alopecia with >50% hair loss and severe telogen effluvium, leading to appropriate treatment strategies and improved patient outcomes.