GJB2 Gene

Palmoplantar keratoderma with deafness is a disorder characterized by skin abnormalities and hearing loss. Affected individuals develop unusually thick skin on the palms of the hands and soles of the feet (palmoplantar keratoderma) beginning in childhood. Hearing loss ranges from mild to profound. It begins in early childhood and gets worse over time. Affected individuals have particular trouble hearing high-pitched sounds.

The signs and symptoms of this disorder may vary even within the same family, with some individuals developing only skin abnormalities and others developing only hearing loss.

Vohwinkel syndrome is a disorder with classic and variant forms, both of which affect the skin.

In the classic form of Vohwinkel syndrome, affected individuals have thick, honeycomb-like calluses on the palms of the hands and soles of the feet (palmoplantar keratoses) beginning in infancy or early childhood. Affected children also typically have distinctive starfish-shaped patches of thickened skin on the tops of the fingers and toes or on the knees. Within a few years they develop tight bands of abnormal fibrous tissue around their fingers and toes (pseudoainhum); the bands may cut off the circulation to the digits and result in spontaneous amputation. People with the classic form of the disorder also have hearing loss.

The variant form of Vohwinkel syndrome does not involve hearing loss, and the skin features also include widespread dry, scaly skin (ichthyosis), especially on the limbs. The ichthyosis is usually mild, and there may also be mild reddening of the skin (erythroderma). Some affected infants are born with a tight, clear sheath covering their skin called a collodion membrane. This membrane is usually shed during the first few weeks of life.

Bart-Pumphrey syndrome is characterized by nail and skin abnormalities and hearing loss.

People with Bart-Pumphrey syndrome typically have a white discoloration of the nails (leukonychia); the nails may also be thick and crumbly. Affected individuals often have wart-like (verrucous) skin growths called knuckle pads on the knuckles of the fingers and toes. They may also have thickening of the skin on the palms of the hands and soles of the feet (palmoplantar keratoderma). The skin abnormalities generally become noticeable during childhood.

The hearing loss associated with Bart-Pumphrey syndrome ranges from moderate to profound and is typically present from birth (congenital).

The signs and symptoms of this disorder may vary even within the same family; while almost all affected individuals have hearing loss, they may have different combinations of the other associated features.

Keratitis-ichthyosis-deafness (KID) syndrome is characterized by eye problems, skin abnormalities, and hearing loss.

People with KID syndrome usually have keratitis, which is inflammation of the front surface of the eye (the cornea). The keratitis may cause pain, increased sensitivity to light (photophobia), abnormal blood vessel growth over the cornea (neovascularization), and scarring. Over time, affected individuals experience a loss of sharp vision (reduced visual acuity); in severe cases the keratitis can lead to blindness.

Most people with KID syndrome have thick, hard skin on the palms of the hands and soles of the feet (palmoplantar keratoderma). Affected individuals also have thick, reddened patches of skin (erythrokeratoderma) that are dry and scaly (ichthyosis). These dry patches can occur anywhere on the body, although they most commonly affect the neck, groin, and armpits. Breaks in the skin often occur and may lead to infections. In severe cases these infections can be life-threatening, especially in infancy. Approximately 12 percent of people with KID syndrome develop a type of skin cancer called squamous cell carcinoma, which may also affect mucous membranes such as the lining of the mouth.

Partial hair loss is a common feature of KID syndrome, and often affects the eyebrows and eyelashes. Affected individuals may also have small, abnormally formed nails.

Hearing loss in this condition is usually profound, but occasionally is less severe.

Hystrix-like ichthyosis with deafness (HID) is a disorder characterized by dry, scaly skin (ichthyosis) and hearing loss that is usually profound. Hystrix-like means resembling a porcupine; in this type of ichthyosis, the scales may be thick and spiky, giving the appearance of porcupine quills.

Newborns with HID typically develop reddened skin. The skin abnormalities worsen over time, and the ichthyosis eventually covers most of the body, although the palms of the hands and soles of the feet are usually only mildly affected. Breaks in the skin may occur and in severe cases can lead to life-threatening infections. Affected individuals have an increased risk of developing a type of skin cancer called squamous cell carcinoma, which can also affect mucous membranes such as the inner lining of the mouth. People with HID may also have patchy hair loss caused by scarring on particular areas of skin.

Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body.

Nonsyndromic hearing loss can be classified in several different ways. One common way is by the condition's pattern of inheritance: autosomal dominant (DFNA), autosomal recessive (DFNB), X-linked (DFNX), or mitochondrial (which does not have a special designation). Each of these types of hearing loss includes multiple subtypes. DFNA, DFNB, and DFNX subtypes are numbered in the order in which they were first described. For example, DFNA1 was the first type of autosomal dominant nonsyndromic hearing loss to be identified.

The characteristics of nonsyndromic hearing loss vary among the different types. Hearing loss can affect one ear (unilateral) or both ears (bilateral). Degrees of hearing loss range from mild (difficulty understanding soft speech) to profound (inability to hear even very loud noises). The term "deafness" is often used to describe severe-to-profound hearing loss. Hearing loss can be stable, or it may be progressive, becoming more severe as a person gets older. Particular types of nonsyndromic hearing loss show distinctive patterns of hearing loss. For example, the loss may be more pronounced at high, middle, or low tones.

Most forms of nonsyndromic hearing loss are described as sensorineural, which means they are associated with a permanent loss of hearing caused by damage to structures in the inner ear. The inner ear processes sound and sends the information to the brain in the form of electrical nerve impulses. Less commonly, nonsyndromic hearing loss is described as conductive, meaning it results from changes in the middle ear. The middle ear contains three tiny bones that help transfer sound from the eardrum to the inner ear. Some forms of nonsyndromic hearing loss, particularly a type called DFNX2, involve changes in both the inner ear and the middle ear. This combination is called mixed hearing loss.

Depending on the type, nonsyndromic hearing loss can become apparent at any time from infancy to old age. Hearing loss that is present before a child learns to speak is classified as prelingual or congenital. Hearing loss that occurs after the development of speech is classified as postlingual.

Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body.

Nonsyndromic hearing loss can be classified in several different ways. One common way is by the condition's pattern of inheritance: autosomal dominant (DFNA), autosomal recessive (DFNB), X-linked (DFNX), or mitochondrial (which does not have a special designation). Each of these types of hearing loss includes multiple subtypes. DFNA, DFNB, and DFNX subtypes are numbered in the order in which they were first described. For example, DFNA1 was the first type of autosomal dominant nonsyndromic hearing loss to be identified.

The characteristics of nonsyndromic hearing loss vary among the different types. Hearing loss can affect one ear (unilateral) or both ears (bilateral). Degrees of hearing loss range from mild (difficulty understanding soft speech) to profound (inability to hear even very loud noises). The term "deafness" is often used to describe severe-to-profound hearing loss. Hearing loss can be stable, or it may be progressive, becoming more severe as a person gets older. Particular types of nonsyndromic hearing loss show distinctive patterns of hearing loss. For example, the loss may be more pronounced at high, middle, or low tones.

Most forms of nonsyndromic hearing loss are described as sensorineural, which means they are associated with a permanent loss of hearing caused by damage to structures in the inner ear. The inner ear processes sound and sends the information to the brain in the form of electrical nerve impulses. Less commonly, nonsyndromic hearing loss is described as conductive, meaning it results from changes in the middle ear. The middle ear contains three tiny bones that help transfer sound from the eardrum to the inner ear. Some forms of nonsyndromic hearing loss, particularly a type called DFNX2, involve changes in both the inner ear and the middle ear. This combination is called mixed hearing loss.

Depending on the type, nonsyndromic hearing loss can become apparent at any time from infancy to old age. Hearing loss that is present before a child learns to speak is classified as prelingual or congenital. Hearing loss that occurs after the development of speech is classified as postlingual.