Cutaneous Ultrastructural Features of the Flaky Skin (Fsn) Mouse Mutation

The study examined the flaky skin (fsn) mouse mutation, an autosomal recessive genetic condition that resembled human psoriasis vulgaris. Affected mice appeared normal at birth but later developed skin abnormalities such as hyperkeratotic plaques, acanthosis, and a thickened epidermis with sparse hair and scale accumulations. Hair shafts exhibited pits and striations, while nails were bent with surface irregularities. Microscopic analysis revealed increased epidermal thickness, mitochondrial aberrations, and neutrophil invasion. Abnormalities in keratohyalin were identified, and macrophages and mast cells were observed near the basement membrane. The papillary dermis showed dense collagen fibers and cellular infiltrates. These findings suggested that the fsn mouse mutation served as a natural model for studying human psoriasis vulgaris.