<unk> , also known as spoon nails, is a nail disease that can be a sign of hypochromic anemia, especially iron-deficiency anemia. It refers to abnormally thin nails (usually of the hand) which have lost their convexity, becoming flat or even concave in shape. In a sense,<unk>  is the opposite of nail clubbing. In early stages nails may be brittle and chip or break easily.<unk>  is associated with Plummer–Vinson syndrome and iron deficiency anemia. It has also been associated with lichen planus, syphilis, and rheumatic fever. The term is from the Greek: κοῖλος, koilos, "hollow", ὄνυξ, onyx, "nail". Even though<unk>  has been associated with iron deficiency in case reports, it is more likely seen as an occupational change in nails and may be idiopathic; ruling out iron deficiency anemia in these patients is the only work-up necessary in this condition.
Koilonychia
Platonychia
Trachonychia
Hapalonychia
Onychoschizia
Onychophosis
Melanonychia
Leukonychia