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Clin Genet. 2014 May;85(5):476-81. doi: 10.1111/cge.12198. Epub 2013 Jun 12.

Mesoaxial polydactyly is a major feature in Bardet-Biedl syndrome patients with LZTFL1 (BBS17) mutations.

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Laboratoire de Génétique Médicale, INSERM U1112, Faculté de Médecine de Strasbourg, Universitaires de Strasbourg, Strasbourg, France.


Ciliopathies are heterogeneous disorders sharing different clinical signs due to a defect at the level of the primary cilia/centrosome complex. Postaxial polydactyly is frequently reported in ciliopathies, especially in Bardet-Biedl syndrome (BBS). Clinical features and genetic results observed in a pair of dizygotic twins with BBS are reported. The following manifestations were present: retinitis pigmentosa, bilateral insertional polydactyly, cognitive impairment and renal dysfunction. X-rays of the hands confirmed the presence of a 4th mesoaxial extra-digit with Y-shaped metacarpal bones. The sequencing of LZTFL1 identified a missense mutation (NM_020347.2: p.Leu87Pro; c.260T>C) and a nonsense mutation (p.Glu260*; c.778G>T), establishing a compound heterozygous status for the twins. A major decrease of LZTFL1 transcript and protein was observed in the patient's fibroblasts. This is the second report of LZTFL1 mutations in BBS patients confirming LZTFL1 as a BBS gene. Interestingly, the only two families reported in literature thus far with LZTFL1 mutations have in common mesoaxial polydactyly, a very uncommon feature for BBS. This special subtype of polydactyly in BBS patients is easily identified on clinical examination and prompts for priority sequencing of LZTFL1 (BBS17).


Bardet-Biedl syndrome; LZTFL1 gene; ciliopathy; mesoaxial polydactyly

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