Wikis > Dermatology > Nail Disorders > Koilonychia

Nail becomes flat or concave (‘spoon’ shaped nails). Surface of nail usually smooth. Could be the result of downward angulation of proximal nail matrix - as nail plate grows forward  resistance forces nail upward. More common in fingers than toes.
Classical feature of iron deficiency/hypochromic anaemia
May be feature in early infancy – usually temporary.
‘Drop of water’ test – drop of water stays on surface of nail.
Nail-patella syndrome is a rare example.

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