Hair Loss
Differential Diagnosis
Common Diagnoses
- Androgenic Alopecia (Male Pattern Baldness)
- Seborrhoeic Dermatitis
- Alopecia Areata
- Contact Allergic Dermatitis
- Tinea Capitis
Occasional Diagnoses
- Bacterial Folliculitis
- Telogen effluvium
- Endocrine: Myxoedema, Hypopituitarism and Hypoparathyroidism
- Traction Alopecia
- Lupus Erythematosus
- Iatrogenic (e.g. Chemotherapy, Anticoagulants)
Rare Diagnoses
- Secondary Syphilis
- Trichotillomania
- Morphoea
- Malnutrition
Ready Reckoner
Key distinguishing features of the most common diagnoses
| Androgenic | Seborrhoeic Dermatitis | Alopecia Areata | Allergic Dermatitis | Tinea Capitis | |
|---|---|---|---|---|---|
| Normal Scalp | Yes | No | Yes | No | No |
| Abnormal Skin on Body | No | Possible | No | Possible | Possible |
| Exclamation Mark Hairs | No | No | Yes | No | No |
| Patchy Hair Thinning | Yes (M) No (F) | Yes | Yes | Yes | Yes |
| Scaling and Weeping | No | Yes | No | Possible | Yes |
Possible Investigations
Likely:None.
Possible:Wood’s light test, hair and scales for mycology.
Small Print:FBC, ESR/CRP, U&E, TFT, FSH/LH, prolactin, autoimmune tests, syphilis serology.
- Microsporum infections will fluoresce green under a Wood’s (UV) light.
- Send scrapings and hair for mycology if the scalp looks abnormal.
- FBC, ESR/CRP and autoimmune tests may help identify autoimmune causes, e.g. SLE.
- Syphilis serology: Old-fashioned, but syphilis is on the increase.
- U&E, TFT, FSH/LH, prolactin will effectively screen for endocrinopathy.
Top Tips
- Alopecia areata is occasionally associated with other autoimmune diseases. Further assessment is sensible, even at a later consultation.
- Remember that in telogen effluvium, the traumatic event – such as a significant illness or childbirth – will have taken place about 4 months before the onset of hair loss, so the connection is unlikely to be made by the patient.
- The patient invariably fears total hair loss – ensure that this is broached and that a realistic prognosis is given.
- Lymphadenopathy in association with alopecia may suggest an infective process – consider bacterial folliculitis.
Red Flags
- Alopecia areata has a particularly poor prognosis if there are several patches, there is loss of eyebrows or eyelashes, or if it begins in childhood.
- Scarring alopecia should prompt the clinician to look for general signs of lupus erythematosus.
- Trichotillomania in children is usually simply due to habit; in adults, though, it is more often a sign of significant psychological disturbance.