subungual haematomaA collection of blood under a nail.
subungual haematomanail bed haematoma usually associated with local trauma, anticoagulant or chemotherapy; may resemble nail bed melanoma
acute subungual haematoma subungual bleeding due to sudden acute trauma (e.g. from a heavy object); initially presents as acutely painful, bluish-grey discoloration of nail bed; treated by nail bed perforation with a drill burr or electrocautery, releasing trapped blood; note: causative trauma may also cause terminal phalanx fracture; established acute haematoma (i.e. > 1 week's duration) resembles chronic subungual haematoma
chronic subungual haematoma chronic leakage of blood between nail plate and bed due to repeated minor trauma (e.g. ill-fitting shoes, repetitive sports-related trauma); presents as reddish-black nail plate discoloration and local onycholysis; nail plate growth carries discoloured area distally to be lost when nail-free margin is cut back (assuming that causative trauma has ceased); treated by general nail care and identification and eradication of cause