A pair of monozygotic twins manifested widespread ichthyosis on the trunk and extremities, mainly on the extensor surface of the lower legs. Both patients had severe developmental retardation, microcephalus, spastic quadriplegia, myoclonus, and hearing impairment. Cranial computed tomography and magnetic resonance imaging revealed diffuse cortical atrophy. Electroencephalography documented diffuse slow wave dysrhythmia and marked epileptic discharges, namely bilateral occipital dominant, and low-voltage multifocal spikes which appeared asynchronously as a burst, mainly during sleep. Skin biopsy revealed hyperkeratosis with parakeratosis. Granular cell layer was not thickened and diminished. Papillomatosis was absent. Electron microscopy did not reveal any distinctive abnormalities. Sjögren-Larsson syndrome and other known ichthyosis syndromes were excluded because of the difference in localization of skin lesions, skin manifestations, lack of papillomatosis, the nature and severity of neurologic symptoms and marked electroencephalographic abnormalities.