Snapshot An 8-year-old girl presents to her pediatrician 2 days after accidentally slamming a door on her index finger. She reports significant throbbing pain after the incident. On physical exam, her right index finger is swollen with a blue-black discoloration under the distal nail. A radiograph reveals no fracture. The physician explains that as the blood has clotted, there is no point in draining the subungual hematoma. (Subungual hematoma) Introduction Nail unit is composed of nail bed paronychium (proximal and lateral nail fold) eponychium (cuticle) lunula Growth is approximately 1 mm per month Subungual Hematoma Clinical definition blood clot under the nail Etiology trauma Presentation blue-black hematoma under the nail plate throbbing pain Treatment trephination indication if the subungual hematoma occurred within 48 hours and has not clotted non-steroidal anti-inflammatory drugs (NSAIDs) indication for all patients Splinter Hemorrhages Clinical definition ruptured nail bed capillaries characterized by narrow lines under the nails Etiology trauma typically associated with the distal nail plate systemic diseases typically associated with the proximal nail plate Associated conditions psoriasis infective endocarditis lichen planus other chronic dermatoses Presentation red or black longitudinal lines under the nail plate Koilonychia Clinical definition upward curving of the distal nail plate also called spoon nail Associated conditions iron deficiency Presentation spoon-shaped upward curving of the distal nail plate Leukonychia Clinical definition white discoloration from the defective keratinization of the distal matrix subtype of leukonychia is Mees lines transverse white striae that run parallel to the nail base Etiology trauma infection drugs arsenic or lead poisoning Demographics children Presentation white discoloration of the nail in patches or striae Beau Lines Clinical definition temporary arrest of the nail matrix proliferation Etiology trauma drugs (retinoids) infection Presentation transverse grooves that move with nail growth Pitting Clinical definition pitting from the abnormal keratinization of the nail matrix Associated conditions psoriasis alopecia areata Presentation “ice pick-like” depressions in the nail Onycholysis Clinical definition separation of the nail from the nailbed Etiology trauma drugs Associated conditions Graves’ disease psoriasis squamous cell carcinoma Presentation white discoloration of the nail plate discoloration is due to air underneath Complication higher risk of dermatophyte nail infections