12 Surprising Causes of Spoon-Shaped Nails (Koilonychia)

Koilonychia, also known as spoon-shaped nails, is a condition where the nails develop a concave, spoon-like appearance. Initially presenting as unusually flat nails, this deformity is most often noticed in the fingernails rather than toenails. Over time, the nails soften, and the indentation in the center becomes prominent enough to hold a droplet of liquid. While koilonychia is common in infants and often resolves on its own, its presence in adults may signal an underlying health issue that requires attention. Treatment typically depends on identifying and addressing the root cause, such as environmental, nutritional, or medical factors. Genetic cases may not be preventable, but many instances linked to lifestyle or nutrition can often be treated or even avoided altogether. In this expanded list, we explore 12 potential causes of koilonychia, shedding light on the surprising factors behind this unique nail condition.

1. Iron Deficiency

The most prevalent cause of koilonychia is a deficiency of iron in an affected individual's body. Iron deficiency occurs most commonly in children and childbearing-aged women. Any of numerous medical issues can cause an individual to develop an iron deficiency. This condition can be the result of an insufficient amount of iron in an individual's diet. A patient may not be able to properly absorb a sufficient amount of iron from the food they consume. Individuals who live in a region plagued with malnutrition and famine also develop iron deficiency easily. Any individual who experiences a bleed in their intestine may develop a deficiency in iron. Patients affected by and being treated for numerous types of cancer also tend to develop iron deficiency anemia. The exact mechanism of which a lack of iron causes the development of koilonychia is not clear, but it is known to be associated with iron deprivation to iron-containing enzymes in the patient's epithelial cells.