Vohwinkel syndrome: A genetic disorder characterized by hearing loss and thickened skin, particularly on the knuckles. The sensorineural hearing is mild-to-moderate in degree. The thickening of the skin (hyperkeratosis) can be "mutilating" and cause autoamputation of the digits. The syndrome is inherited in an autosomal dominant manner. It is caused by mutation in the GJB2 gene (connexin 26). The mutation is the replacement of aspartic acid with histidine at position 66 in the protein's chain of amino acids. This mutation is also written as Asp66His.