<prompt> Characteristic nail finding in lichen planus?PittingPterygiumBeaus linesHyperpigmentation of nails  <response>: The nail changes in Lichen planus include: - Irregular longitudinal grooving and ridging of the nail plate. - Pterygium formationMost characteristic - Shedding of the nail plate with atrophy of nail bed. - Subungual hyperkeratosis. - Subungual Hyperpigmentation. Pterygium: Loss of small area of the nail plate with proximal nail fold epidermis adherent to the nail bed epidermis pterygium unguis. Inverse pterygium is seen in systemic sclerosis. 1. Pitting- i Psoriasis- Irregular deep pits Thimble pittingii Alopecia- Superficial regular pits iii Eczema 2. Beaus lines- trauma, hypocalcaemia, malnutrition3. Hyperpigmentation of nails- infection,drugs, dyes, melanoma, etc 