Olmsted syndrome, also known as mutilating palmoplantar keratoderma (PPK) with periorificial keratotic plaques, is a very rare congenital (present from birth) disorder causing abnormal growth and thickening of skin. The most common affected areas are the palms of the hand, the soles of the feet, and the area around the eyes and mouth. Other symptoms include sparse hair and abnormal nails, joint abnormalities, pain, and itching. The abnormal skin thickening in Olmsted syndrome tends to get worse over time. People with this condition are at increased risk for infections and for skin cancer. Olmsted syndrome is caused by genetic changes (DNA variants) in the TRPV3 and the MBTPS2 gene. Many different forms of inheritance have been reported, although many cases of Olmsted syndrome are sporadic (a new case in a family). Diagnosis is based on the symptoms, and genetic testing can be helpful.