Two cases of keratosis follicularis squamosa (Dohi) caused by swimsuit friction.

Keratosis follicularis squamosa (KFS) is a keratinizing disorder that is characterized by asymptomatic small scaly patches with follicular plugs scattered on the trunk and thighs. Irritation by clothing, bacterial infections, heredity and hormone imbalances have all been proposed as pathogenic factors. Case 1 involved an 11-year-old Japanese female who presented with a 1-year history of small patches on the lateral chest. She had been attending swimming classes for seven years. A histological examination showed dilated hair follicles with keratotic plugs. A bacterial culture of the lesion detected Staphylococcus auricularis. Case 2 involved a 5-year-old Japanese female who presented with a 1-year history of eruptions on the lateral trunk. The eruptions appeared after she began to attend swimming classes. The physical and histological findings of Case 2 were similar to those of Case 1. A bacterial culture test detected Staphylococcus capitis. Both cases were diagnosed as KFS. The patient in Case 1 changed her swimsuit and was treated with 50 mg of oral minocycline daily. The patient in Case 2 stopped attending swimming classes without receiving any treatment. The skin lesions in both cases completely disappeared within a few months. The clinical courses of these patients suggest that swimsuit friction was the cause of KFS.