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    Bart-Pumphrey Syndrome

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    Definition

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

    1. Introduction

    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.

    2. Frequency

    Bart-Pumphrey syndrome is a rare disorder; its exact prevalence is unknown. Only a few affected families and individual cases have been identified.

    3. Causes

    Bart-Pumphrey syndrome is caused by mutations in the GJB2 gene. This gene provides instructions for making a protein called gap junction beta 2, more commonly known as connexin 26. Connexin 26 is a member of the connexin protein family. Connexin proteins form channels called gap junctions that permit the transport of nutrients, charged atoms (ions), and signaling molecules between neighboring cells that are in contact with each other. Gap junctions made with connexin 26 transport potassium ions and certain small molecules.

    Connexin 26 is found in cells throughout the body, including the inner ear and the skin. In the inner ear, channels made from connexin 26 are found in a snail-shaped structure called the cochlea. These channels may help to maintain the proper level of potassium ions required for the conversion of sound waves to electrical nerve impulses. This conversion is essential for normal hearing. In addition, connexin 26 may be involved in the maturation of certain cells in the cochlea. Connexin 26 also plays a role in the growth, maturation, and stability of the outermost layer of skin (the epidermis).

    The GJB2 gene mutations that cause Bart-Pumphrey syndrome change single protein building blocks (amino acids) in the connexin 26 protein. The altered protein probably disrupts the function of normal connexin 26 in cells, and may interfere with the function of other connexin proteins. This disruption could affect skin growth and also impair hearing by disturbing the conversion of sound waves to nerve impulses.

    4. Inheritance

    This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

    5. Other Names for This Condition

    • knuckle pads, deafness, and leukonychia syndrome
    • knuckle pads, leukonychia, and sensorineural deafness

    This entry is adapted from https://medlineplus.gov/genetics/condition/bart-pumphrey-syndrome

    References

    1. Alexandrino F, Sartorato EL, Marques-de-Faria AP, Steiner CE. G59S mutation inthe GJB2 (connexin 26) gene in a patient with Bart-Pumphrey syndrome. Am J MedGenet A. 2005 Jul 30;136(3):282-4.
    2. Lee JR, White TW. Connexin-26 mutations in deafness and skin disease. ExpertRev Mol Med. 2009 Nov 19;11:e35. doi: 10.1017/S1462399409001276. Review.
    3. Ramer JC, Vasily DB, Ladda RL. Familial leuconychia, knuckle pads, hearingloss, and palmoplantar hyperkeratosis: an additional family with Bart-Pumphreysyndrome. J Med Genet. 1994 Jan;31(1):68-71.
    4. Richard G, Brown N, Ishida-Yamamoto A, Krol A. Expanding the phenotypicspectrum of Cx26 disorders: Bart-Pumphrey syndrome is caused by a novel missense mutation in GJB2. J Invest Dermatol. 2004 Nov;123(5):856-63.
    5. Xu J, Nicholson BJ. The role of connexins in ear and skin physiology -functional insights from disease-associated mutations. Biochim Biophys Acta. 2013Jan;1828(1):167-78. doi: 10.1016/j.bbamem.2012.06.024.
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