Bardet-Biedl Syndrome

It is named after Georges Louis Bardet, a French physician (born 1885) and after Artur Biedl, a Hungarian pathologist and endocrinologist (born 1869).

Bardet-Biedl syndrome (BBS) is a familial condition.

• Bedouins and the Arab population of Kuwait have an incidence of 1:13,500.
• A high incidence (1:17,500) is also found in Newfoundland. 1:160,000 elsewhere.
• Ratio male:female approximately 1·3:1

Although it had been originally thought to be a recessive disorder, it has been demonstrated that some forms of Bardet-Biedl syndrome require recessive mutations in 1 of the 6 loci, plus an additional mutation in a second locus.¹ This has been called 'triallelic inheritance', or 'recessive inheritance with a modifier of penetrance'.

Fourteen forms have been identified with differing phenotypes:²

• There are only subtle differences among Bardet-Biedl families with BBS1, BBS2, or BBS4 forms. The most obvious feature is that affected offspring in the BBS1 category are taller than their parents. Affected subjects in the BBS2 and BBS4 groups were significantly shorter than their parents.
• BBS3 patients have polydactyly limited to the lower limbs, average IQ, and obesity reversible by calorie restriction and/or exercise.
• In reported case series of BBS 5 no patients had polydactyly, but all had brachydactyly and/or syndactyly. All had severe visual impairment with retinal macular changes, and there was hypogonadism in the 2 males examined.

• Growth and development: Mental and growth retardation
• Behaviour and performance: Poor visual acuity and blindness
• Eyes: Rod-cone dystrophy (sometimes called atypical retinitis pigmentosa), myopia, strabismus, and cataracts
• Hand and foot: Polydactyly, syndactyly or brachydactyly
• Cardiovascular system: Hypertrophy of interventricular septum and left ventricle and dilated cardiomyopathy
• Gastrointestinal system: Hepatic fibrosis, central obesity and diabetes mellitus
• Urogenital system: Hypogonadism, renal failure,⁴ urogenital sinuses, ectopic urethra, uterus duplex, septate vagina, and hypoplasia of the uterus, ovaries, and fallopian tubes.

• Laurence-Moon syndrome; where affected individuals have a spastic paraparesis, but no polydactyly
• Cohen syndrome (CS)

There are no specific treatments for the characteristics associated with Bardet-Biedl syndrome.

• As vision worsens, individuals will benefit from the use of low-vision aids and orientation as well as from mobility training.
• To manage the complications of renal disease, every individual with the disorder should be examined by a renal physician.

Prognosis is very poor where renal failure occurs.