koilonychia

Koilonychia is a nail abnormality where the normally convex nail plate becomes thin, flattened, and eventually concave, giving a spoon-like appearance. The pathophysiology is thought to relate to impaired keratin synthesis in the nail matrix due to deficient iron-dependent enzymes, since iron is a cofactor for enzymes involved in epithelial cell proliferation and keratinization. Clinically, koilonychia is most classically associated with severe, chronic iron deficiency anemia, often seen alongside other signs such as pallor, fatigue, glossitis, angular cheilitis, and pica. It is part of the classic triad (with dysphagia and esophageal web) seen in Plummer-Vinson syndrome, which occurs in the setting of chronic iron deficiency. Other associations include hemochromatosis (paradoxically), Raynaud's disease, systemic lupus erythematosus, thyroid disease, and trauma or occupational exposure to petroleum-based solvents. In infants, mild koilonychia can be a normal variant. On boards, koilonychia in the context of microcytic anemia should immediately raise suspicion for iron deficiency anemia, and the underlying cause of the iron deficiency (e.g., GI blood loss, malnutrition, menorrhagia) should be investigated.