Coffin-Siris syndrome (CSS) is a rare congenital multi-systemic genetic disorder characterized by aplasia or hypoplasia of the distal phalanx or nail of the fifth digit, developmental delay, intellectual disability, coarse facial features, and other variable clinical manifestations.

Short distance from the end of the finger to the most distal interphalangeal crease or the distal interphalangeal joint flexion point. That is, hypoplasia of one or more of the distal phalanx of finger.