Curly fingernails developed in a 35-year-old female during etretinate therapy (0.25 mg/kg per day) given for chronic palmoplantar pustulosis. Before treatment some of the fingernails showed slight distal onycholysis without dystrophy or irregularity of the nail plate. The suggested mechanism of this phenomenon is a stimulatory effect on nail growth rate expressed on normal matrix differentially from matrix with pre-existing pathology.