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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