Longitudinal melanonychia after healing of lichen planus

A patient with progressive longitudinal ridging, diffuse pigmentation and narrowing of the finger nails as the only signs of lichen planus was treated with intramuscular injections of triamcinolone for 2 years. Her nails healed, with the appearance of normal proximal nails after 6 months. After one year, longitudinal bands of melanonychia appeared on the thumbs and still persist.