Walczak-Sztulpa et al. Orphanet Journal of Rare Diseases (2020) 15:36 https://doi.org/10.1186/s13023-020-1303-2 RESEARCH Open Access Compound heterozygous IFT140 variants in two Polish families with Sensenbrenner syndrome and early onset end-stage renal disease Joanna Walczak-Sztulpa1* , Renata Posmyk2†, Ewelina M. Bukowska-Olech1†, Anna Wawrocka1, Aleksander Jamsheer1, Machteld M. Oud3,4, Miriam Schmidts3,5, Heleen H. Arts6,7, Anna Latos-Bielenska1 and Anna Wasilewska8 Abstract Background: Sensenbrenner syndrome, which is also known as cranioectodermal dysplasia (CED), is a rare, autosomal recessive ciliary chondrodysplasia characterized by a variety of clinical features including a distinctive craniofacial appearance as well as skeletal, ectodermal, liver and renal anomalies. Progressive renal disease can be life-threatening in this condition. CED is a genetically heterogeneous disorder. Currently, variants in any of six genes (IFT122, WDR35, IFT140, IFT43, IFT52 and WDR19) have been associated with this syndrome. All of these genes encode proteins essential for intraflagellar transport (IFT) a process that is required for cilium assembly, maintenance and function. Intra- and interfamilial clinical variability has been reported in CED, which is consistent with CED’s genetic heterogeneity and is indicative of genetic background effects. Results: Two male CED patients from two unrelated Polish families were included in this study. Clinical assessment revealed distinctive clinical features of Sensenbrenner syndrome, such as dolichocephaly, shortening of long bones and early onset renal failure. Ectodermal anomalies also included thin hair, short and thin nails, and small teeth in both patients. Next generation sequencing (NGS) techniques were performed in order to determine the underlying genetic cause of the disorder using whole exome sequencing (WES) for patient 1 and a custom NGS-based panel for patient 2. Subsequent qPCR and duplex PCR analysis were conducted for both patients. Genetic analyses identified compound heterozygous variants in the IFT140 gene in both affected individuals. Both patients harbored a tandem duplication variant p.Tyr1152_Thr1394dup on one allele. In addition, a novel missense variant, p.(Leu109Pro), and a previously described p.(Gly522Glu) variant were identified in the second allele in patients 1 and 2, respectively. Segregation analysis of the variants was consistent with the expected autosomal recessive disease inheritance pattern. Both patients had severe renal failure requiring kidney transplantation in early childhood. Conclusion: The finding of compound heterozygous IFT140 mutations in two unrelated CED patients provide further evidence that IFT140 gene mutations are associated with this syndrome. Our studies confirm that IFT140 changes in patients with CED are associated with early onset end-stage renal disease. Moreover, this report expands our knowledge of the clinical- and molecular genetics of Sensenbrenner syndrome and it highlights the importance of multidisciplinary approaches in the care of CED patients. Keywords: Sensenbrenner syndrome, Cranioectodermal dysplasia, IFT140, Ciliopathy, End-stage renal disease * Correspondence: [email protected] †Renata Posmyk and Ewelina M. Bukowska-Olech contributed equally to this work. 1Department of Medical Genetics, Poznan University of Medical Sciences, Rokietnicka 8 Street, 60-608 Poznan, Poland Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Walczak-Sztulpa et al. Orphanet Journal of Rare Diseases (2020) 15:36 Page 2 of 10 Background Patient 1 Sensenbrenner syndrome is an ultra-rare autosomal A 3.5-years-old boy was referred to the Genetic Coun- recessive disorder that is thought to result from dys- seling Unit due to renal failure, skeletal abnormalities function of cilia. CED is a genetically heterogeneous and ocular problems. The patient was born to young disease affecting multiple systems. It is diagnosed (20-year-old mother and 33-year-old father), unrelated based on characteristic clinical features, which include parents from a first, unremarkable pregnancy, by con- sagittal craniosynostosis, dolichocephaly, facial dys- ventional vaginal delivery in the 39th week of gestation. morphisms such as epicanthal folds, telecanthus, The birth weight was 3700 g (50th -75th centile), length hypertelorism and frontal bossing, growth retardation, 57 cm (97th centile), head circumference 36 cm (75th– shortening of upper and lower limbs, narrow thorax, 97th centile), and thorax circumference 33 cm (25-50th protuberant abdomen, progressive renal disease and centile). The Apgar score was 9 at 1 min. The family his- ectodermal abnormalities. Liver and retinal dysfunc- tory was unremarkable. Although the family doctor re- tion have also been reported in CED patients, albeit corded proteinuria, hematuria and glycosuria in the less frequently [1, 2]. early neonatal period, no further evaluation was con- To date, more than 60 patients have been reported in ducted. At the age of 12 months the child was treated literature and mutations in six genes have been associ- for a urinary tract infection. At three years of age, he de- ated with Sensenbrenner syndrome: IFT122, WDR35, veloped bronchopneumonia and was hospitalized in a dis- IFT140, IFT43, IFT52 and WDR19 [3–8]. All of these trict hospital, where elevated creatinine levels were genes encode proteins that are involved in intraflagellar detected. The child was referred to the Pediatric transport (IFT). This is a bi-directional transport process Nephrology Department for further diagnosis. Routine that occurs in the cilium and plays a crucial role in laboratory investigations showed constant proteinuria, cilium assembly, maintenance and function. The IFT140 glycosuria, hematuria, eGFR (Schwartz)- 30,56 ml/ protein is part of the so-called IFT-A complex that pri- min/1.73 m2, elevated serum levels of creatinine, uric marily regulates retrograde intraflagellar ciliary transport acid and urea, total cholesterol, and triglyceride were (i.e., transport of cargo proteins from the ciliary tip to its determined, whereas complete blood count, blood base). The IFT140 gene consists of 31 exons (29 coding glucose, albumin, thyroid and liver function tests were exons) and encodes a 1462 amino acid protein that con- normal. Ultrasonography of kidneys showed increased tains five WD repeats and nine tetratricopeptide (TPR) renal cortex echogenicity and decreased cortico- repeats [9–11]. medullary differentiation. Mutations in IFT122 and WDR35 are the most Distinctive dysmorphic features were observed dur- common cause of CED and explain about 60% of ing the first assessment by a clinical geneticist at the families with Sensenbrenner syndrome. To date, only age of 3.5 years. The features included dolichocephaly, two unrelated CED patients with IFT140 variants have high forehead, thin hair, full cheeks, low set promin- been reported in literature [8, 12]. IFT140 mutations ent ears, long philtrum, microretrognathia, rhizomelic thus constitute a relatively uncommon cause of CED. shortening of upper and lower limbs, brachydactyly of However, clinical phenotypes associated with dysfunc- toes and fingers, narrow chest and pectus excavatum. tion of IFT140 are not limited to CED. In fact, patho- These features, in combination with progressive renal genic variation in IFT140 has also been reported in failure, were indicative of a ciliopathy (Fig. 1 a-d and patients with Mainzer-Saldino Syndrome (MSS), Jeune Table 1). Ophthalmological examination confirmed Syndrome (JATD), Opitz trigonocephaly C syndrome strabismus, nystagmus and high hyperopia. Cytogen- (OTCS), and isolated retinal dystrophy [13, 14]. CED, etic analysis (conventional GTG banding) revealed a MSS and JATD are phenotypically and genetically related normal male karyotype (46,XY). The patient was seen disorders, and are collectively referred to as short-rib thor- in the genetics clinic every 6 months. Renal function acic dysplasia syndromes [15]. The identification of vari- rapidly declined in the following 12 months. At the ants in IFT140 in patients with various, overlapping age of 4.5 years the patient had developed end-stage phenotypic features is in line with the general presump- renal failure and peritoneal dialysis was ordered. At tion that ciliopathies represent a spectrum of disorders the age of 6.5 years, his weight was 19.3 kg (25th– with marked phenotypic and genotypic overlap among 50th centile), his height was 102 cm (< 3rd centile), distinctly-classified conditions. and his BMI was 18,55 kg/m2 (97th centile). His mor- phological phenotype markedly differed from the pre- Clinical examination vious clinical assessments during the last examination In our study two male patients from two unrelated, non- at the age of 9 years (Fig. 1 e-h). Short stature, obes- consanguineous Polish families were diagnosed with ity, short fingers and