New Bardet-Biedl syndrome gene

Posted by & filed under Part 29: EYE, Part 30: MULTISYSTEM INBORN ERRORS OF DEVELOPMENT.

Nat Genet. 2006 May;38(5):521-4. Epub 2006 Apr 2.
BBS10 encodes a vertebrate-specific chaperonin-like protein and is a major BBS
locus.

Stoetzel C. et al.

This french group identified a new gene mutated in up to 20% of the patients with Bardet-Biedl syndrome.

For information on retinitis pigmentosa which affects patients with Bardet-Biedl syndrome, please see chapter 235.

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Philippe Campeau, MD
Resident in Medical Genetics at McGill University
OMMBID Blog Administrator

One Response to “New Bardet-Biedl syndrome gene”

  1. pcampeau

    FROM CHAPTER 235

    Retinitis Pigmentosa as Part of a Multisystem Disease

    In most cases, patients with retinitis pigmentosa or cone-rod degeneration have no associated systemic or extraocular abnormalities. However, there are multisystem diseases in which a retinal degeneration similar to retinitis pigmentosa or cone-rod dystrophy is a part. Although rare, the most noteworthy are diseases for which effective treatment is available to ameliorate the retinal degeneration. These are abetalipoproteinemia (MIM 200100; see Chap. 115), Refsum disease (MIM 266510; see Chap. 132), gyrate atrophy (see Chap. 83), and recessive retinitis pigmentosa and Friedrich-like ataxia due to defective 0x0003b1-tocopherol transfer protein.86,87 It should be noted briefly here that patients with abetalipoproteinemia or ataxia due to defective 0x0003b1-tocopherol transport protein can recover retinal function after therapy with vitamin A88,89 or vitamin E,90 respectively. With regard to Refsum disease, dietary modification aimed at reducing the intake of phytanic acid levels is of benefit in slowing or stopping the associated retinal degeneration.91 Similarly, patients with gyrate atrophy appear to benefit from a diet that restricts the intake of ornithine precursors.92

    A substantial minority patients with retinitis pigmentosa report some degree of hearing deficiency. In most of these cases, the combination of hearing loss and retinitis pigmentosa is usually inherited together as an autosomal recessive trait that is termed Usher syndrome. Usher syndrome has been divided into three major types according to clinical findings. In Usher syndrome type I, retinitis pigmentosa is associated with vestibular ataxia and profound congenital deafness93-99; in Usher syndrome type II, there is retinitis pigmentosa with partial hearing loss100; and in Usher syndrome type III, there is retinitis pigmentosa and progressive hearing loss.101 Most cases of Usher syndrome type II are due to a gene on chromosome 1q41. Most cases of Usher syndrome type III are due to an unidentified gene on chromosome 3q21-24. At least six genes (on chromosomes 10q, 11p15.1, 11q13.5, 14q32, 21q21, and elsewhere99) can cause Usher syndrome type I, one of which encodes myosin VIIa (Table 235-1). There is a solitary family reported with a dominantly inherited syndrome of retinitis pigmentosa, hearing impairment, and subclinical myopathy caused by a mitochondrial mutation.102

    Table 235-1: Chromosome Assignments of Genes Causing Retinal Degeneration or Stationary Night Blindness

    Some other multisystem diseases in which retinal degeneration is a feature are Bardet-Biedl syndrome (recessive retinitis pigmentosa associated with polydactyly, truncal obesity, hypogonadism, short stature, and mental retardation),103-107 dominant cerebellar ataxia with pigmentary macular dystrophy,108-110 Batten disease (recessive neuronal ceroid lipofuscinosis; see Chap. 154),111,112 and the syndrome of X-linked macular degeneration, congenital ataxia, and late-onset progressive myoclonic encephalopathy.113 Retinitis pigmentosa is also a feature of Kearns-Sayre syndrome (external ophthalmoplegia, pigmentary retinal degeneration, and cardiomyopathy), due to a deletion in the mitochondrial genome114-116 (see Chap. 105). Additional types of syndromic retinal degeneration are listed in Table 235-1.

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