COMMON CAUSES IN ADULTS:

Vitiligo is acquired often progressive disorder of hypopigmentation, discussed in details by me in another article.
Idiopathic guttate hypomelanosisis presents with small white to light brown patches on shins and forearms in females beyond the age of 40 years.
Tinea versicolor is caused by yeast, and is characterised by small white patches with fine scales on the surface mostly distributed on the upper back and chest.
Post inflammatory hypomelanosis as the name suggests ocurs as a result of damage to the pigment forming cells in various skin disorders like psoriasis, herpes zoster, secondary syphillis, sarcoidosis, mycosis fungoidosis etc.
Post-traumatic leukoderma occurs when the pigment forming cells are damaged due to any kind of physical trauma to skin like accidents, ulcers, burns etc.
Pressure leukoderma occurs due to constant pressure on skin for prolonged time, and is commonly seen in Indian females over waist, as a result of tightly tying a Sari.
Chemical-induced lekoderma occurs at the site of contact of chemicals like:
- On feet: because Azo dyes in ALTS.
- On forehead because of Para-tertiary butylphenol in Bindi adhesive.
- On feet due to straps of rubber slippers.
- Monobenzyl ether of hydroquinone commonly found in purse causes depigmentation over area of contact.
Halo nevi is charectrised by development of white border around existing mole.
Lichen sclerosis characteritically has thinning of skin in the areas white patches.
Morphea on the other hand has thick & hard skin along with white patches.