🧑‍⚕️ Alopecia refers to hair loss from the scalp or body. It is classified into scarring (permanent follicle destruction) and non-scarring (potentially reversible). Causes range from genetics and autoimmune disease to drugs, stress, endocrine disorders, and infections. Identifying the type is essential for accurate management and prognosis.

Dihydrotestosterone (DHT) is a potent androgen formed from testosterone by the enzyme 5α-reductase. It binds androgen receptors more strongly than testosterone and acts locally in tissues such as the scalp, prostate, and skin. In hair follicles, DHT shortens the anagen (growth) phase and miniaturises follicles, leading to androgenetic alopecia in genetically susceptible individuals. Clinically, this mechanism underlies male- and female-pattern hair loss, and therapies like finasteride target DHT production to slow hair loss.

🧑‍⚕️ Alopecia Overview – Pathophysiology, Clinical Features & Management

Type of Alopecia	Pathophysiology & Key Features	Management / Red Flags 🚨
💇‍♂️ Androgenetic Alopecia	DHT-mediated follicle miniaturisation 🧬; men: receding temples/crown; women: diffuse crown thinning. Non-scarring, progressive.	Topical minoxidil ✅; oral finasteride (men) 💊; hair transplantation optional; gentle hair care. Non-urgent.
🩹 Alopecia Areata	Autoimmune T-cell attack on follicles ⚔️; patchy hair loss, exclamation mark hairs, nail pitting; can progress to totalis/universalis.	Topical/intralesional corticosteroids 💉; immunotherapy (diphenylcyprone) for resistant cases; monitor for other autoimmune disease ⚠️.
🌪️ Telogen Effluvium	Premature shift anagen → telogen 💨 due to stress, illness, postpartum, drugs; diffuse shedding, non-scarring, self-limiting.	Reassurance ✅; remove triggers; monitor regrowth; supportive care; usually resolves 3–6 months.
🪢 Traction Alopecia	Chronic mechanical tension on follicles 🔗; hairline recession, broken hairs, scalp tenderness; early = reversible, chronic → scarring.	Stop tight hairstyles ✅; topical steroids if inflamed; hair transplant if chronic; monitor for permanent loss 🚨.
🔥 Scarring Alopecia (Cicatricial)	Permanent follicle destruction by chronic inflammation ⚡ (lichen planopilaris, lupus, burns); shiny scalp, absent follicular openings, erythema, scaling.	Urgent dermatology referral 🚨; systemic/topical immunosuppressants (steroids, hydroxychloroquine, mycophenolate); early intervention critical.
🧴 Non-Scarring Alopecia	Follicles intact; hair loss due to endocrine, nutritional, or medication causes; patchy/diffuse; regrowth possible.	Treat underlying cause ✅ (thyroid, iron, nutrition, meds); topical minoxidil optional; monitor for progression to scarring ⚠️.

⚠️ Causes & Pathophysiology

🧬 Genetic predisposition (male/female pattern hair loss, familial cases of alopecia areata).
🛡️ Autoimmune: T-cell-mediated attack on hair follicles (alopecia areata, lupus).
🔄 Hormonal: Thyroid dysfunction, androgen excess (PCOS), menopause.
💊 Drugs: Chemotherapy (follicular arrest), anticoagulants, lithium, beta-blockers.
🥗 Nutritional: Iron, vitamin D, zinc deficiencies → impaired follicle cycling.
😥 Stress / illness: Cytokine-mediated anagen → telogen shift.
🦠 Infections: Tinea capitis, folliculitis, viral infections.
✂️ Trauma / traction: mechanical stress → follicular inflammation, possible scarring.
🧴 Inflammatory dermatoses: eczema, psoriasis, lichen planus affecting scalp.

🔎 Clinical Clues

Patchy or diffuse hair loss; sudden shedding or slow thinning.
Scarring alopecia: shiny scalp, loss of follicular openings.
Pruritus, tenderness, or burning on affected areas.
Exclamation mark hairs → alopecia areata.
Nail pitting with autoimmune alopecia.

🧪 Diagnosis

History & Physical: Pattern, onset, triggers, medication review, family history.
Bloods: TFTs, ferritin, vitamin D, autoimmune screen, androgen levels (if indicated).
Scalp biopsy: Essential if scarring alopecia suspected or diagnosis uncertain.
Trichoscopy: Dermoscopic features: yellow dots (alopecia areata), black dots, absence of follicular openings (scarring).

💊 Management

Medications:
- Minoxidil topical – first-line for androgenetic alopecia.
- Finasteride oral – men only, inhibits DHT.
- Corticosteroids: topical/intralesional – alopecia areata.
- Immunotherapy: diphencyprone, topical sensitizers for resistant alopecia areata.
Procedures:
- Hair transplantation – androgenetic alopecia.
- Platelet-rich plasma (PRP) therapy.
- Scalp micropigmentation – cosmetic option.
Lifestyle: Gentle hair care, avoid traction hairstyles, balanced diet, stress management.
Alternative / Adjunct: Limited evidence for rosemary oil, acupuncture.

📌 Summary & Exam Pearls

Classify as scarring (irreversible) vs non-scarring (reversible) alopecia.
Androgenetic: DHT-mediated, patterned thinning.
Alopecia areata: Autoimmune, exclamation mark hairs, nail pitting; can progress to totalis/universalis.
Telogen effluvium: Diffuse shedding post-stress, illness, postpartum.
Red flag: Scarring alopecia → urgent dermatology referral.

📚 UK Guidance & References

NICE Clinical Knowledge Summary – Hair Loss in Adults: https://cks.nice.org.uk/topics/hair-loss-adults/
British Association of Dermatologists – Guidelines for Alopecia: https://www.bad.org.uk/
DermNet NZ – Alopecia Overview: https://dermnetnz.org/topics/alopecia/

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Alopecia ✅