Further audiovestibular characterization of DFNB77, caused by deleterious variants in LOXHD1, and investigation into the involvement of Fuchs corneal dystrophy.

This study focuses on further characterization of the audiovestibular phenotype and on genotype-phenotype correlations of DFNB77, an autosomal recessive type of hearing impairment (HI). DFNB77 is associated with disease-causing variants in LOXHD1, and is genetically and phenotypically highly heterogeneous. Heterozygous deleterious missense variants in LOXHD1 have been associated with late-onset Fuchs corneal dystrophy (FCD). However, up to now screening for FCD of heterozygous carriers in DFNB77 families has not been reported. This study describes the genotype and audiovestibular phenotype of 9 families with DFNB77. In addition, carriers within the families were screened for FCD. Fifteen pathogenic missense and truncating variants were identified, of which 12 were novel. The hearing phenotype showed high inter- and intrafamilial variation in severity and progression. There was no evidence for involvement of the vestibular system. None of the carriers showed (pre-clinical) symptoms of FCD. Our findings expand the genotypic and phenotypic spectrum of DFNB77, but a clear correlation between the type or location of the variant and the severity or progression of HI could not be established. We hypothesize that environmental factors or genetic modifiers are responsible for phenotypic differences. No association was found between heterozygous LOXHD1 variants and the occurrence of FCD in carriers.

Delayed diagnosis and underreporting of congenital anomalies associated with oral clefts in the Netherlands: a national validation study.

OBJECTIVE: Since 1997, the 15 Dutch cleft palate teams have reported their patients with oral clefts to the national oral cleft registry (NVSCA). During the first visit of the patient to the team - which is usually within the first year of life - the oral cleft and associated congenital anomalies are recorded through a unique recording form by a plastic surgeon/orthodontist/paediatrician. In this study, we evaluated the quality of data on congenital anomalies associated with clefts. METHODS: We drew a random sample of 250 cases registered in the national database with oral clefts from 1997 through 2003; of these, 13 were excluded. Using two independent reregisters derived from two-phased medical data review, we analysed whether associated anomalies were correctly diagnosed and recorded. RESULTS: The agreement on associated anomalies between the NVSCA and medical data ranged from moderate to poor (kappa 0.59 to 0). Seventy-seven percent of the craniofacial anomalies were underreported in the NVSCA: 30% due to delayed diagnosis and 47% due to deficient recording. Additionally, 80% of the associated anomalies of other organ systems were underreported: 52% due to delayed diagnosis and 28% due to deficient recording. The reporting of final diagnoses was somewhat better; however, 54% were still underreported (24% delayed diagnosis and 30% deficient recording). The rate of overreporting was 1.6% or lower. CONCLUSION: Congenital anomalies associated with clefts are underreported in the NVSCA because they are under diagnosed and deficiently recorded during the first consultations with the cleft palate teams. Our results emphasise the need for routine and thorough examination of patients with clefts. Team members should be more focussed on co-occurring anomalies, and early genetic counselling seems warranted in most cases. Additionally, our findings underline the need for postnatal follow-up and ongoing registration of associated anomalies; reregistration in the NVSCA at a later age is recommended.

Prenatal ultrasound screening for orofacial clefts.

OBJECTIVES: To evaluate the sensitivity and specificity of ultrasound for detecting prenatal facial clefts in low-risk and high-risk populations. METHODS: This study prospectively followed up a non-selected population, namely all pregnant women who underwent routine second-trimester prenatal ultrasound screening in the Utrecht region during the 2-year period from January 2007 to December 2008. RESULTS: A total of 35 924 low-risk and 2836 high-risk pregnant women underwent ultrasound screening. Orofacial clefts were present in 62 cases, an incidence of 1:624. The distribution of clefts was as follows: 18 (29%) cleft lip, 25 (40%) cleft lip with cleft palate, 17 (27%) cleft palate only, one median cleft and one atypical cleft. Of these, 38 (61%) were unilateral and 23 (37%) were bilateral. Thirty-nine per cent (24/62) had associated anomalies, with most chromosomal defects found in the cleft lip with cleft palate and cleft palate only groups. Cleft lip with or without cleft palate was detected prenatally in 38/43 cases, a sensitivity of 88%. No case of cleft palate only was detected prenatally. There were three false-positive cases, of which two were fetuses with multiple congenital deformities. CONCLUSIONS: Ultrasound screening has a high sensitivity for the detection of cleft lip with and without cleft palate in high-risk and low-risk pregnancies in our region, where well-trained sonographers carry out primary screening. The key to a high sensitivity of prenatal ultrasound is likely to be a combination of excellent training of sonographers, referral to specialized centers when a cleft is suspected, routine visualization of the fetal face and advances in ultrasound techniques.

Clinical spectrum of SIX3-associated mutations in holoprosencephaly: correlation between genotype, phenotype and function.

BACKGROUND: Holoprosencephaly (HPE) is the most common structural malformation of the human forebrain. There are several important HPE mutational target genes, including the transcription factor SIX3, which encodes an early regulator of Shh, Wnt, Bmp and Nodal signalling expressed in the developing forebrain and eyes of all vertebrates. OBJECTIVE: To characterise genetic and clinical findings in patients with SIX3 mutations. METHODS: Patients with HPE and their family members were tested for mutations in HPE-associated genes and the genetic and clinical findings, including those for additional cases found in the literature, were analysed. The results were correlated with a mutation-specific functional assay in zebrafish. RESULTS: In a cohort of patients (n = 800) with HPE, SIX3 mutations were found in 4.7% of probands and additional cases were found through testing of relatives. In total, 138 cases of HPE were identified, 59 of whom had not previously been clinically presented. Mutations in SIX3 result in more severe HPE than in other cases of non-chromosomal, non-syndromic HPE. An over-representation of severe HPE was found in patients whose mutations confer greater loss of function, as measured by the functional zebrafish assay. The gender ratio in this combined set of patients was 1.5:1 (F:M) and maternal inheritance was almost twice as common as paternal. About 14% of SIX3 mutations in probands occur de novo. There is a wide intrafamilial clinical range of features and classical penetrance is estimated to be at least 62%. CONCLUSIONS: Our data suggest that SIX3 mutations result in relatively severe HPE and that there is a genotype-phenotype correlation, as shown by functional studies using animal models.