A NOVEL NONEPIDERMOLYTIC PALMOPLANTAR KERATODERMA - A CLINICAL AND HISTOPATHOLOGIC STUDY OF 6 CASES

Background: Some hereditary palmoplantar keratodermas (PPK) have been defined at the molecular level. Objective: Our purpose was to establis h the cause of a hereditary PPK with unique histopathologic findings i n the epidermis. Methods: Investigative studies included light and ele ctron microscopy and determination of genomic DNA sequence. Results: S ix patients with PPK were found to have unique changes in the epidermi s characterized by orthokeratosis, parakeratosis, perinuclear vacuoliz ation, and keratohyalin granules that varied in size and shape and wer e located in the cell periphery. Electron microscopy showed the perinu clear region contained many ribosomes and vacuoles and was surrounded by a tonofibril shell. Family involvement suggested a dominant disorde r. However, no mutation of keratin genes 1, 6a, 9, or 16 was found. Co nclusion: The histopathologic features of this unique PPK most closely resemble Curth-Macklin ichthyosis for which the genetic basis has not been established. Further genetic studies are needed.