Onychomadesis is a spontaneous nail shedding that most often results as a reaction to a viral exanthem, most commonly the enteroviral exanthems.

A Beau line is a transverse depression in the nail plate that grows distally with the growth of the nail.

Both onychomadesis and beau's lines result from a temporary interruption of nail formation.

Most common associations in children include: coxsackie infection, febrile illnesses, Kawasaki disease, periungual inflammation, or trauma.

When there is only partial interruption of the nail matrix activity a single transverse groove appears at the proximal nail fold that moves outward with nail growth. This is referred to as a Beau line (Fig. 9.18).

When the trigger interrupts nail matrix function completely then there is onychomadesis where there is complete separation of the nail plate (Fig. 9.19).

Normal fingernail growth is 1 mm per week. The Beau line or the completely separated nail will move outward as normal new nail grows. New nail growth is usually complete by 4 to 6 months.