A 16-year-old, blonde-haired patient was evaluated for a new band of lighter-colored hair located approximately 3 cm from the scalp. The patient first noted the change in hair color 1 week after returning from a 2-week vacation in Costa Rica, during which she took chloroquine phosphate for malaria prophylaxis.Instead of taking 500 mg weekly, the recommended dose for prophylaxis, the patient took 500 mg of chloroquine phosphate daily, starting 1 week before the trip, during the 2 weeks in Costa Rica, and for 1 week after returning home. She had taken the first dose 3.5 months before presentation. Hair hypopigmentation is a rare but reversible side effect of chloroquine.
Although most cases occur after 3 consecutive months of treatment with daily doses of more than 500 mg of the drug, rapid onset is also possible.