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The water-drop test for the diagnosis of koilonychia

      Koilonychia is a common concave nail dystrophy in which the nail plate is depressed centrally and elevated laterally.
      • Walker J.
      • Baran R.
      • Vélez N.
      • Jellinek N.
      Koilonychia: an update on pathophysiology, differential diagnosis and clinical relevance.
      The term has Greek origins, with koilos meaning spoon. The pathophysiology of koilonychia, or spoon nails, is poorly understood. It has been associated with dermatologic disorders such as alopecia areata, psoriasis, and lichen planus; endocrinopathies such as hypothyroidism, hyperthyroidism, and diabetes mellitus; nutritional deficiencies, notably iron deficiency anemia; genodermatoses; and traumatic and occupational exposures. The workup for koilonychia is based on the patient's history, review of systems, and physical examination.
      • Walker J.
      • Baran R.
      • Vélez N.
      • Jellinek N.
      Koilonychia: an update on pathophysiology, differential diagnosis and clinical relevance.
      Koilonychia is an important clinical finding because it might be a clue to a dermatologic or systemic disease. Although the diagnosis of koilonychia is made clinically, the nail concavity might be subtle on clinical examination (Fig 1). Complex mathematics is required to measure nail convexity; thus, taking measurements is not practical or feasible in the clinical setting.
      Figure thumbnail gr1
      Fig 1Koilonychia of the thumbnails. The nail plates are depressed centrally and everted laterally. The concavity is sometimes difficult to distinguish on physical examination.

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      References

        • Walker J.
        • Baran R.
        • Vélez N.
        • Jellinek N.
        Koilonychia: an update on pathophysiology, differential diagnosis and clinical relevance.
        J Eur Acad Dermatol Venereol. 2016; 30: 1985-1991
        • Witts L.
        Chronic microcytic anaemia.
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