Allopecia - Differential Diagnosis Framework for Hair Loss
Localized / Focal Hair Loss Pattern:
• Scarring Alopecia:
- Infectious: Dissecting cellulitis of the scalp, Folliculitis decalvans, Tinea Capitis
- Skin Disease: Discoid lupus erythematosus, Keratosis follicularis (KFSD), Lichen planopilaris, Frontal fibrosing alopecia, Pseudopelade of Brocq, Alopecia mucinosa, Aplasia Cutis
• Non-Scarring Alopecia:
- Hair Shafts Intact or Absent: Alopecia areata (+Nail pitting), Alopecia syphilitica
- Broken Hair Shafts: Tinea Capitis, Trichotillomania, Pressure-induced (postoperative) alopecia, Traction alopecia
Diffuse Hair Loss Pattern:
• Scarring Alopecia: Lupus erythematosus, Lichen planopilaris
• Non-Scarring Alopecia:
- Pattern: Androgenetic alopecia in men (male pattern hair loss), Female pattern hair loss
- Anagen Effluvium: Chemotherapy/Cytotoxic Drugs, Loose anagen syndrome
- Patches: Alopecia totalis, Alopecia universalis
- Telogen Effluvium
• Endocrine: Hypothyroidism, Hypopituitarism, Post partum
• Dietary: Iron deficiency, Zinc deficiency, Copper deficiency, Vitamin A excess, Vitamin D deficiency
• Drugs: Oral contraceptives, Lithium
• Stress: Post op, Post infection, Psychologic stress
Physical Examination:
• Signs of any comorbid disease
• Pull test
• Dry, broken hair suggests trichorrhexis nodosa
• Scaling, pustules, crusts, erosions, or erythema and local adenopathy suggest infection
• Examine the entire skin surface, nails, and teeth
• Boggy texture at bald spots associated with fungi
Initial Laboratory Tests:
• TSH
• Serum iron & ferritin
• RPR
• Laboratory evaluation for hyperandrogenism (Prolactin, FSH, LH, DHEAS)
• ANA
• Vitamin D levels
Systemic Disorders:
• Major illness or surgeries
• Major psychologic stress
• Significant weight loss
• Chronic iron deficiency
• Thyroid disorders
• Childbirth
• Poisoning from arsenic, mercury, or thallium
• Drugs
• Poor diet (caloric or protein restriction)
• Hormonal disorder
• Atopic dermatitis
• Seborrheic Dermatitis (Consider HIV)
• Contact dermatitis
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