Cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma (CEDNIK) syndrome is a rare autosomal recessive disorder caused by a loss of function mutation in SNAP29, encoding SNARE protein. These mutations lead to abnormal maturation of lamellar granules and subsequent mislocation of epidermal lipids and proteases. Neurological deficits are severe and may appear within the first few months of life. Hypotonia gives rise to poor feeding and failure to thrive. Further manifestations include global developmental delay, neuropathy, and microcephaly with intellectual disability. Facial dysmorphisms are variable and include an elongated facies, slanted eyes, hypertelorism, and a flat, broad nasal root. The dermatologic findings of palmoplantar keratoderma and ichthyosis appear between the ages of 5 and 11 months, with progressive worsening in the second year of life.

Phenotypic variations, such as onset in early childhood rather than in infancy and patients with SNAP29 mutations without dermatologic manifestations, have been described.

The prognosis for this condition is poor, ranging from neonatal lethality to a lifespan of approximately 20 years.