A case of unilateral koilonychia with rapid response to combined treatment with vitamin B12 and folic acid

Introduction Koilonychia, also called spoon-shaped nail, is a nail deformity characterized by concavity of the nail plate. Its diagnosis is based on clinical findings. Koilonychia can be idiopathic, genetic, or acquired due to related causes such as anemia, malnutrition, trauma, or thyroid hormone dysregulation. Case A 20-year-old woman presented with deformity of the nails on her right hand for 2 weeks. The patient stated that her hands had been intermittently exposed to chlorine bleach (sodium hypochlorite 5.25%) for household cleaning for about 3 months. Dermatologic examination revealed thinning, fragility, concavities in the distal part of the nails, and orangish discoloration in the second to fifth nails on the right hand. These findings were compatible with koilonychia. Examination of the left-hand nails was normal. A vitamin B12 level of less than 100 ng/L and folate level of 3.59 ng/mL were detected. A clinical diagnosis of sodium hypochlorite–induced koilonychia was made. The patient was recommended to stop contact with chlorinated bleach and to stop household cleaning. The following medications were started: 1000 mcg/ml cyanocobalamin administered by intramuscular injection once a week and 5 mg/day folic acid administered orally. No topical treatment was applied to the nails. After 1 month, it was observed that the koilonychia regressed. Discussion Our case is valuable in terms of the association of vitamin B12 and folic acid deficiencies with unilateral koilonychia and the rapid improvement of koilonychia due to vitamin B12 and folic acid replacement. In conclusion, this preliminary observation suggests the need to check vitamin B12 and folic acid levels in patients with unilateral koilonychia and that replacement of these vitamins in cases of deficiency may be part of the treatment for koilonychia.