In medical terminology, wooly hair refers to several rare conditions where an anomaly in the structure of the scalp causes the growth of fragile, very tightly curled hair. The three most common forms are wooly hair nevus, which is a condition where kinky hair grows in one or more clearly defined areas of the scalp apart from non-curly hair; hereditary wooly hair, where the hair is mainly present in infancy and childhood; and familial wooly hair, which is present from birth and is often associated with skin and heart abnormalities. These conditions are congenital, meaning they are present from birth, and only occur in people of Caucasian descent. In most people, the curls are more noticeable in childhood than adulthood. There are no medical treatments, though the patches of curly hair in wooly hair nevus can be excised surgically.
Symptoms include very tight curls of hair that are no more than 0.2 inches (0.5 cm) in diameter, and that tend to join together, making the hair difficult to brush or comb. The hair is also often short, because it is so fragile that the hair shafts break off before they grow to be very long. It is recommended to avoid any harsh hair treatments, such as bleaching, coloring or straightening, when one has this condition.
This is a cutaneous condition, meaning it involves the surface-area of the body, including the hair, skin and nails. It is sometimes associated with other cutaneous conditions and other physical abnormalities. For example, persons with wooly hair nevus sometimes suffer from skin lesions and abnormal development of bone and teeth. Naxos syndrome, a form of familial wooly hair, is associated with a form of heart disease that affects the right chamber of the heart muscle. Persons with this syndrome also often have skin abnormalities called keratoses on the scalp, palms and soles of the feet.
Scientists do not fully understand the genetics of all types of this condition and have not found a specific gene responsible. Hereditary forms of this condition do run in families and is a dominant trait, meaning a child will have kinky hair even if the genetic trait is passed on by only one parent. It appears to be a recessive trait, meaning it only shows up if it is inherited from both parents. The genetic anomalies causing Naxos syndrome have been identified, but the genes responsible for wooly hair nevus are still unknown.