#1. Is the hair loss localised (patchy) or generalised?
- Hair loss that conforms to the typical male-pattern baldness, or the less well-known female version (thinning of the hair over the vertex), is probably due to the normal androgenic hormones - androgenic aloplecia.
- Well-circumscribed patches that develop suddenly with a normal scalp underneath are most likely aloplecia areata.
- Alternatively, localised hair loss can reflect a localised scarring process (e.g. a burn).
- Finally, significant traction on the hair - e.g. hairdressing techniques, or even psychiatric disorders - can cause hair loss. This can be generalised, but it usually only in the areas of the applied force.
#2. Is the underlying scalp normal or scarred?
A scarred underlying scalp reflects the end-point of many processes - for instance: burns, scalp infections, traction injuries and even metastatic deposits.
More commonly, the underlying scalp is normal, and the hair loss is generalised. In this case, the list is long, so it's helpful to subdivide the causes a bit. For instance:
- Hormonal - pregnancy, puerperium, virilisation
- Metabolic/Nutritional - thyroid dysfunction, iron deficiency
- Drugs - corticosteroids, androgens, cytotoxics, anticonvulsants, allopurinol, methyldopa, etc.
- Infections - (secondary) syphilis
The list isn't exhaustive, but it's always helpful to have access to a broad schema for common presentations. Hope that helps.