Cause:

• Common causes:
  • Iron deficiency anemia (Plummer Vinson syndrome), malnutrition, hemochromatosis
  • Occupational softening
• Other causes:
  • Coronary disease
  • Thyroid disorders
  • Upper gastrointestinal malignancy
  • Traumatic injury, or occupational
  • Subungual hyperkeratosis accompanying koilonychias is suggestive of psoriasis

Fingernails with koilonychia and trachyonychia (nail pitting) | Singal A, Arora R. Nail as a window of systemic diseases. Indian Dermatol Online J. 2015 Mar-Apr;6(2):67-74. doi: 10.4103/2229-5178.153002. PMID: 25821724; PMCID: PMC4375768.