To the Editor.—
Canities (graying of hair) is progressive and permanent and is usually regarded as a normal manifestation of the aging process. Loss of pigment is associated with a gradual reduction in melanocyte tyrosinase activity and eventual loss of functional melanocytes.1 The age of onset and progression is genetically determined and usually proceeds in an orderly fashion. Premature canities, defined as the onset of graying before the age of 20 years in whites or the age of 30 years in blacks, may be an isolated familial trait associated with other autoimmune disorders, such as pernicious anemia, vitamin B12 and iron deficiency, hyperthyroidism and hypothyroidism, and Addison's hypoadrenalism, in the premature aging syndromes or other inherited disorders or in severe cases of malnutrition.2 Drugs, such as chloroquine, hydroxychloroquine, mephenesin, triparanol, and fluorobutyrophenone, are reported to cause hair lightening by an unknown mechanism.2 In general, graying of the hair is progressive and permanent, except for repigmentation associated with alopecia areata and vitiligo.
Tobin DJ, Cargnello JA. Partial Reversal of Canities in a 22-Year-Old Normal Chinese Male. Arch Dermatol. 1993;129(6):789-791. doi:10.1001/archderm.1993.01680270133025