### Date : 2025-07-23 19:05
### Topic : 2.1 Alopecia and Its Types
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### 1. Androgenetic Alopecia (AGA)
**Definition & Pathogenesis:**
- The most common form of hair loss, affecting males and females.
- Due to genetic susceptibility and androgen sensitivity, specifically dihydrotestosterone (DHT)-induced follicular miniaturization.
**Clinical Presentation:**
- **Men:** Characteristic progressive frontal and temporal recession, vertex thinning (Norwood-Hamilton scale).
- **Women:** Diffuse thinning of the mid-scalp and crown with preservation of the frontal hairline (Ludwig or Sinclair scales).
**Diagnostic Approach:**
- Clinical examination: classic patterns.
- Trichoscopy: follicular miniaturization, variation in hair shaft diameter (>20%), yellow dots, peripilar signs.
- Histology (if necessary): perifollicular fibrosis, reduced terminal-to-vellus hair ratio.
**Management:**
- Medical therapy: Minoxidil (topical), Finasteride (oral), Dutasteride (oral), anti-androgens in women (e.g., spironolactone).
- Adjunctive treatments: Platelet-rich plasma (PRP), low-level laser therapy (LLLT).
- Surgical management: Hair transplantation (FUE/FUT).
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### 2. Alopecia Areata (AA)
**Definition & Pathogenesis:**
- Autoimmune non-scarring alopecia characterized by T-cell mediated attack on hair follicles.
**Clinical Presentation:**
- Sudden onset of clearly demarcated, round patches of hair loss.
- "Exclamation mark hairs" (short hairs tapered proximally) at lesion periphery.
- Can progress to Alopecia Totalis (entire scalp) or Alopecia Universalis (entire body).
**Diagnostic Approach:**
- Clinical examination: discrete, sharply defined patches.
- Trichoscopy: exclamation-mark hairs, black dots, broken hairs, yellow dots.
- Histology (if needed): lymphocytic infiltrate around anagen hair bulbs ("swarm of bees").
**Management:**
- First-line: Intralesional corticosteroids.
- Second-line: Topical corticosteroids, Minoxidil.
- Severe cases: Systemic corticosteroids, JAK inhibitors (e.g., tofacitinib, baricitinib).
- Counseling due to unpredictable disease course.
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### 3. Telogen Effluvium (TE)
**Definition & Pathogenesis:**
- Diffuse, non-scarring hair shedding due to abnormal transition of anagen hairs into telogen phase, commonly following physical, psychological, or metabolic stress.
**Clinical Presentation:**
- Acute (within months of triggering event) or chronic (>6 months).
- Increased shedding of hairs diffusely from the scalp without clear patches.
- Typically reversible once underlying factor is addressed.
**Diagnostic Approach:**
- Clinical history: identify potential triggers (surgery, childbirth, illness, medications, emotional stress).
- Hair pull test: positive (increased number of telogen hairs).
- Trichoscopy: absence of miniaturization (normal hair shaft diameter), short regrowing hairs.
- Laboratory tests: identify nutritional deficiencies (ferritin, vitamin D, thyroid profile).
**Management:**
- Correct underlying cause (stress reduction, nutritional supplementation, medication adjustments).
- Patient reassurance about the self-limiting nature of TE.
- Consider Minoxidil for accelerated regrowth in chronic TE.
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### 4. Scarring Alopecias (Cicatricial Alopecias)
Permanent hair loss due to irreversible destruction of hair follicles, replaced by scar tissue.
Common examples:
#### ① Frontal Fibrosing Alopecia (FFA)
- **Definition & Pathogenesis:** Variant of lichen planopilaris, inflammatory lymphocytic attack on hair follicles, primarily in post-menopausal women.
- **Clinical Presentation:** Progressive symmetrical frontal and temporal recession with perifollicular erythema and loss of eyebrows.
- **Diagnosis:** Clinical recognition, Trichoscopy (absence of follicular openings, perifollicular scaling and erythema), scalp biopsy (lymphocytic infiltrate).
- **Management:** Early initiation of topical/intralesional corticosteroids, systemic anti-inflammatory/immunomodulatory agents (hydroxychloroquine, dutasteride).
#### ② Lupus-related Alopecia (Discoid Lupus Erythematosus, DLE)
- **Definition & Pathogenesis:** Scarring alopecia secondary to autoimmune connective tissue disorder causing chronic inflammation and scarring.
- **Clinical Presentation:** Scaly plaques, follicular plugging, erythema, hypopigmentation, scarring patches predominantly affecting scalp and face.
- **Diagnosis:** Clinical appearance, ANA profile, scalp biopsy (interface dermatitis, basement membrane thickening).
- **Management:** Photoprotection, topical and intralesional corticosteroids, systemic antimalarials (hydroxychloroquine), immunosuppressants for severe cases.
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