Clin Genet 2013 Printed in Singapore. All rights reserved © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd CLINICAL GENETICS doi: 10.1111/cge.12198 Short Report Mesoaxial polydactyly is a major feature in Bardet–Biedl syndrome patients with LZTFL1 (BBS17 ) mutations Schaefer E, Lauer J, Durand M, Pelletier V, Obringer C, Claussmann A, Braun J-J, Redin C, Mathis C, Muller J, Schmidt-Mutter C, Flori E, Marion V, Stoetzel C, Dollfus H. Mesoaxial polydactyly is a major feature in Bardet–Biedl syndrome patients with LZTFL1 (BBS17 ) mutations. Clin Genet 2013. © John Wiley & Sons A/S. Published by John Wiley & Sons Ltd, 2013 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 ). Conflict of interest None. E Schaefer a,† , J Lauer a,† , M Durand a , V Pelletier b , C Obringer a , A Claussmann a , J-J Braun c , C Redin d , C Mathis e , J Muller d,f , C Schmidt-Mutter e , E Flori g , V Marion a , C Stoetzel a and H Dollfus a,b a Laboratoire de G ´ en ´ etique M ´ edicale, INSERM U1112, Facult ´ e de M ´ edecine de Strasbourg, Universitaires de Strasbourg, Strasbourg, France, b Centre de R´ ef ´ erence pour les Affections Rares en G´ en ´ etique Ophtalmologique (CARGO), c Service Oto-Rhino-Laryngologie et Chirurgie Cervico-Faciale, H ˆ opitaux Universitaires de Strasbourg, Strasbourg, France, d D´ epartement de Neurobiologie et G ´ en ´ etique, Laboratoire de Bioinformatique et G ´ enomique Int ´ egratives, Institut de G ´ en ´ etique et de Biologie Mol ´ eculaire et Cellulaire, Illkirch-Graffenstaden, France, e Centre d’Investigation Clinique de Strasbourg, CIC-P 1002, f Laboratoire de Diagnostic G´ en ´ etique, and g Laboratoire de Cytog ´ en ´ etique, H ˆ opitaux Universitaires de Strasbourg, Strasbourg, France † Both the authors contributed equally to this work Key words: Bardet–Biedl syndrome – ciliopathy – LZTFL1 gene – mesoaxial polydactyly Corresponding author: H´ el ` ene Dollfus, Laboratoire de G´ en ´ etique M ´ edicale, INSERM U1112, Facult ´ e de M ´ edecine de Strasbourg, Universit ´ e de Strasbourg, Strasbourg, France. Tel.: +33388128120; fax : +33388128125; 1