EPOS

European Paediatric Ophthalmological Society

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28 The phenotype of bardet-biedl patients with mutations in the BBS4 gene

Riise, R.¹, Tornqvist, K.², Wright, A,F.³, Sheffield, V.C.⁴
Department of Ophthalmology, Central Hospital of Hedmark, Hamar, Norway., Department of Ophthalmology, University Hospital of Lund, Lund, Sweden, MRC Human Genetics Unit, Western General Hospital, Edinburgh, Scotland., Department of Ophthalmology, University of Iowa, Iowa City, Iowa, USA.

Purpose:To describe the phenotype-genotype relation in Norwegian patients with various mutations in the BBS4 gene.

Methods:We have examined 6 Norwegian Bardet-Biedl patients - 3 pairs of siblings - in whom three different mutations in the BBS4 gene on chromosome 15 newly were detected. Four of the patients were homozygous.

Results:All had an increased Body-Mass-Index. The obesity was moderate in 4 individuals with two different mutations, while it was profuse in 2 persons with the same mutation. All had brachydactyly and dental anomalies. All the males had micropenis. Three patients with three different mutations had polydactyly located to the hands, and another two with different mutations had polydactyly located to the feet, one had no polydactyly at all. Mental retardation was suspected in 2 individuals with the same mutation, while the intelligence in the remaining 4 was evaluated to be within normal range. One of the males had spinal stenosis with paraparesis of his legs. None had diabetes or abnormal renal function. Retinal dystrophy was present in all. The age of onset of impaired dark vision ranged from 2 to 7 years. The retinal pigmentations appeared at late stages in all. But the shape of the pigmentations was probably related to the genotype.

Conclusion:The clinical picture in Bardet-Biedl syndrome patients with mutations in the BBS4 gene seem mostly to be independant of the specific mutation. An exception is possibly the retinal pigmentations. Furthermore - the clinical signs in patients with BBS4 gene mutations can not be used to distinguish these patients from Bardet-Biedl patients with mutations in other BBS genes.