Charles Bonnet syndrome in patients with Stargardt disease: prevalence and risk factors.

AIMS: To describe the prevalence of the Charles Bonnet syndrome (CBS) and search for potential CBS risk factors in a Dutch Stargardt disease (STGD1) cohort. METHODS: Eighty-three patients with STGD1 were screened for CBS. They underwent a full eye examination. All patients completed the social functioning domain of the 36-Item Short Form Health Survey questionnaire. Participants suspected of CBS were interviewed to further evaluate their visual hallucinations. RESULTS: CBS prevalence was 8.4%. Six out of seven patients with CBS were women. CBS was not associated with age (p=0.279, Mann-Whitney). Patients with CBS had a significant lower social functioning score (p<0.05, Mann-Whitney). All seven patients with CBS were in the category of vision impairment (visual acuity <6/12, but ≥3/60). Moreover, first hallucinations manifested after a drop in visual acuity. The retinal atrophic area of the worst eye tended to be lower in the CBS group (range 0.11-9.86 mm2) as compared with controls (range 0-180 mm2). There was no relation between the position of the scotoma and the location of the visual hallucinations. CONCLUSION: The relative high CBS prevalence in STGD1 suggests that CBS may be more prevalent in younger ophthalmic patients than currently presumed. In this specific group of patients, we established social isolation and acquired vision impairment as risk factors for CBS. There was a female preponderance among patients with CBS. Age and retinal pigment epithelium atrophy were not identified as significant risk factors. We should actively diagnose CBS in patients of any age who fulfil the criteria for the category vision impairment, especially in cases where social isolation is suspected.

Retinal Capillary Abnormalities in Sjögren-Larsson Syndrome Maculopathy.

Sjögren-Larsson syndrome (SLS) is a neurometabolic disease with a peculiar crystalline maculopathy. It is yet unclear if vascular abnormalities play a role in SLS maculopathy pathogenesis. We used optical coherence tomography angiography (OCT-A) to search for vessel abnormalities in SLS maculopathy. We performed a cross-sectional study in 4 patients (2 males, 2 females, aged 12-36 years) with various stages of SLS maculopathy. Besides OCT-A imaging, a complete ophthalmological examination and additional retinal imaging by transversal and en face spectral domain (SD) OCT were performed. OCT-A images were qualitatively assessed for vascular abnormalities, and imaging was compared to eight eyes of four healthy controls. On OCT-A, all eyes of patients with SLS showed a reduced capillary density around the fovea, and an enlarged foveal avascular zone (FAZ; SLS patients [n = 6 eyes] mean 0.70 mm2 [SD 0.18]; healthy controls [n = 8 eyes] mean 0.34 mm2 [SD 0.07], p = 0.004). In 2 patients, telangiectatic vessels were seen in the deep capillary layer. In conclusion, OCT angiography showed capillary paucity and morphological vessel abnormalities in these 4 patients with SLS.

Recurrence of paraproteinemic crystalline keratopathy after corneal transplantation: A case of monoclonal gammopathy of ocular significance.

PURPOSE: To report the long-term follow-up (12 years) of a 36-year-old male patient with crystalline keratopathy of both eyes, diagnosed with monoclonal gammopathy of undetermined significance (MGUS). Complete ophthalmic, systemic, and corneal immunohistochemical evaluations were performed. OBSERVATIONS: Slit-lamp examination revealed bilateral fine iridescent confluent crystalline deposits in all layers of the cornea, both peripherally and centrally. Systemic evaluation revealed abnormal M protein, IgG-kappa type, in blood and urine. Bone marrow aspiration showed a monoclonal plasma cell concentration of 2%. Consequently, the patient was diagnosed with MGUS. Because of progressive bilateral visual loss in the following 10 years, a perforating keratoplasty was performed on the left eye. Immunohistochemical analysis of the native cornea (the corneal button) revealed depositions of the same M protein type as detected in plasma and urine. Electron microscopy showed rhomboid-shaped corneal deposits of various sizes up to 4 µm. Recurrence of crystalline keratopathy was observed 9 months after keratoplasty. The monoclonal protein remained stable and the MGUS did not progress to multiple myeloma nor a related disorder. CONCLUSIONS AND IMPORTANCE: Crystalline keratopathy may be associated with MGUS in otherwise healthy individuals. If the keratopathy causes binocular visual loss, a corneal transplantation may be required. Unfortunately, recurrence of crystalline deposits in the corneal graft may occur within one year. This suggests that patients with vision impairment due to paraproteinemic keratopathy who are diagnosed as MGUS, in fact, have a monoclonal gammopathy of ocular significance (MGOS).

Retinal Morphology in Sjögren-Larsson Syndrome on OCT: From Metabolic Crystalline Maculopathy to Early-Onset Macular Degeneration.

PURPOSE: To study long-term macular changes by spectral-domain (SD) OCT in patients with Sjögren-Larsson syndrome (SLS). DESIGN: Retrospective cohort study. PARTICIPANTS: Twenty-two patients with genetically proven SLS (12 female, 10 male; median age, 21 years; range, 3-47 years) were included in the study. One or more SD-OCT scans were available from the period 2008 to 2017. METHODS: Seventeen patients underwent SD-OCT imaging of the macula in 2017. Earlier scans were available of the other 5 patients. The latest available SD-OCT scans were qualitatively assessed for morphologic changes in 19 patients. In addition, retinal layer thickness could be measured in 15 patients. The latest scans were compared with previous scans to assess the course of the disease qualitatively (n = 15 patients) and quantitatively (n = 10 patients). MAIN OUTCOME MEASURES: Macular morphology and retinal layer thickness on SD-OCT scans during the study period. RESULTS: In all patients, abnormal macular morphology was observed in both eyes, already from the youngest age. Intraretinal crystals, visible as hyperreflective dots, were visible in all eyes and located in the retinal nerve fiber layer, inner plexiform layer, and outer plexiform layer. Furthermore, the photoreceptor (PR) layer lacked the physiologic thickness amplification beneath the fovea. Pseudocysts with limited interruption of the underlying PR layer were observed in half of the patients, all younger than 30 years of age. Frank atrophy of the retinal pigment epithelium (RPE) and a neovascular complex were seen in 3 older patients and 1 older patient, respectively. The fovea was significantly thinner compared with healthy controls and decreased even further during the study period. CONCLUSIONS: Macular dystrophy in SLS may initially comprise an arrest in foveal development. Because of the absence of macular pigment, phototoxic damage may then cause central retinal degeneration of the vulnerable macula, marked by the development of pseudocysts. Eventually, the young adult patients may proceed to an early-onset end-stage macular degeneration with frank atrophy of the RPE or neovascularization.

Ocular findings in Noonan syndrome: a retrospective cohort study of 105 patients.

The aim of this retrospective study is to describe ocular findings in a large Noonan syndrome cohort and to detect associations between ocular features and genetic mutations that were not found in earlier studies. We collected ophthalmological and genetic data of 105 patients (median age, 12 years; range, 0-60 years) clinically diagnosed as Noonan syndrome. The ocular findings were linked to the genotypes. All patients with Noonan syndrome showed multiple abnormalities in the categories of vision and refraction, external ocular features, ocular alignment and motility, anterior ocular segment, and posterior ocular segment. In total, 50 patients have NS due to a mutation in PTPN11. Permanent visual impairment (bilateral best-corrected visual acuity < 0.3) was found in 7 patients, including patients with a mutation in RAF1, SHOC2, and KRAS. Keratoconus was found in 2 PTPN11 positive patients, and prominent corneal nerves were observed in a patient with a SOS1 mutation. CONCLUSIONS: This study shows an overview of ocular abnormalities in Noonan syndrome, including permanent visual impairment caused by binocular optic nerve abnormalities and nystagmus. Delay in ophthalmological diagnosis is still present, also in patients with visual impairment. All Noonan syndrome patients should have a complete ophthalmological examination at the time of diagnosis. What is Known: • Although we discover more pathogenic mutations in patients with Noonan syndrome, Noonan syndrome still is a clinical diagnosis • Ocular features of Noonan syndrome are characterized by developmental anomalies of the eyelids and associated with other ocular abnormalities in childhood (including refractive errors, strabismus and amblyopia). What is New: • There seems to be a delay in the ophthalmological diagnosis and awareness of the broad variety ofophthalmological features including refractive errors and visual impairment in Noonan syndrome is needed. All children should have a full ophthalmological examination at the time of diagnosis. • Permanent visual impairment (best-corrected visual acuity < 0.3) is found in patients with mutations in RAF1, SHOC2, and KRAS and the cause is probably a developmental disorder of the optic nerves.

Ocular Manifestations of Noonan Syndrome: A Prospective Clinical and Genetic Study of 25 Patients.

PURPOSE: To determine the full spectrum of ocular manifestations in patients with Noonan syndrome (NS). DESIGN: Prospective cross-sectional clinical and genetic study in a tertiary referral center. PARTICIPANTS: Twenty-five patients with NS (mean age, 14 years; range, 8 months-25 years) clinically diagnosed by validated criteria. METHODS: All patients were examined by the same team following a detailed study protocol. Genetic analyses were performed in 23 patients. MAIN OUTCOME MEASURES: Ocular abnormalities of vision and refraction, external ocular features, ocular position and motility, anterior segment, posterior segment, and intraocular pressure. RESULTS: Ocular features of vision and refraction were amblyopia (32%), myopia (40%), and astigmatism (52%). External ocular features were epicanthic folds (84%), hypertelorism (68%), ptosis (56%), high upper eyelid crease (64%), lower eyelid retraction (60%), abnormal upward slanting palpebral fissures (36%), downward slanting palpebral fissures (32%), and lagophthalmos (28%). Orthoptic abnormalities included strabismus (40%), abnormal stereopsis (44%), and limited ocular motility (40%). Anterior segment abnormalities included prominent corneal nerves (72%) and posterior embryotoxon (32%). Additional ocular features were found, including nonglaucomatous optic disc excavation (20%), relatively low (<10 mmHg) intraocular pressure (22%), and optic nerve hypoplasia (4%). Mutations were established in 22 patients: 19 PTPN11 mutations (76%), 1 SOS1 mutation, 1 BRAF mutation, and 1 KRAS mutation. The patient with the highest number of prominent corneal nerves had an SOS1 mutation. The patient with the lowest visual acuity, associated with bilateral optic nerve hypoplasia, had a BRAF mutation. Patients with severe ptosis and nearly total absence of levator muscle function had PTPN11 mutations. All patients showed at least 3 ocular features (range, 3-13; mean, 7), including at least 1 external ocular feature in more than 95% of the patients. CONCLUSIONS: Noonan syndrome is a clinical diagnosis with multiple genetic bases associated with an extensive variety of congenital ocular abnormalities. Ocular features of NS are characterized by 1 or more developmental anomalies of the eyelids (involving the position, opening, and closure) associated with various other ocular abnormalities in childhood, including amblyopia, myopia, astigmatism, strabismus, limited ocular motility, prominent corneal nerves, and posterior embryotoxon.

Ectopia lentis et pupillae in four generations caused by novel mutations in the ADAMTSL4 gene.

OBJECTIVES: To identify the phenotype, genetic defect and inheritance pattern of ectopia lentis et pupillae (ELP) in a large Dutch family, previously diagnosed as presumed autosomal dominant ELP because of the occurrence of ELP in three generations. DESIGN: A clinical and genetic study of children and adults. PARTICIPANTS: Eight patients of the ELP family, including five new patients from the youngest generation. METHODS: Standard ophthalmological examinations were performed. For molecular genetic analysis, the coding region of ADAMTSL4 was sequenced. Main outcome measures were the ocular phenotype of the new ELP patients, the inheritance pattern and the identification of mutations in the ADAMTSL4 gene in the family. RESULTS: Of the eight patients with ectopia lentis, seven fulfilled the clinical diagnostic criteria of ELP. Molecular genetic analysis of these seven patients disclosed two novel mutations in the ADAMTSL4 gene: homozygous (p.Q752X/p.Q752X) in six patients and compound heterozygous (p.Q752X/p.Q758fs) in one patient. Heterozygosity in phenotypically normal parents proved autosomal recessive (AR) inheritance. The pseudodominant inheritance pattern can be explained by high carrier frequency in this small community and/or consanguinity. CONCLUSIONS: Patients from a family with ELP in four generations have AR ELP caused by novel mutations in ADAMTSL4. The clinical presentation of ELP can be variable, but all patients of our study with homozygous p.Q752X mutation have ectopia lentis and pupillary dysfunction in common.

Clinical follow-up and histopathology of the temporal bones in Nathalie syndrome.

The Nathalie syndrome (OMIM 255990) comprises a combination of features that do not resemble any other known syndrome and is as such an independent, rare entity. It is characterized by sensorineural hearing impairment, juvenile cataract, spinal muscular atrophy, skeletal abnormalities, retardation of growth, underdeveloped secondary gender characteristics and cardiomyopathy. Worldwide, only one family with this syndrome is known. An update of the clinical follow-up in this family and the results of autopsy are given. Audiometry showed a downsloping configuration that corresponded to the findings at histopathological examination of the cochlea: a diffuse atrophy of the organ of Corti, severe and diffuse atrophy of the stria vascularis and moderate loss of cochlear neurons in all turns. Another new striking feature is that individuals with the Nathalie syndrome have a shortened life expectancy with a risk of sudden death or death from heart failure resulting from (dilated) cardiomyopathy.

Patients with Sjögren-Larsson syndrome lack macular pigment.

PURPOSE: Sjögren-Larsson syndrome (SLS), an autosomal recessive hereditary disorder with congenital ichthyosis, spastic diplegia or tetraplegia, and mental retardation, reveals a characteristic macular dystrophy with intraretinal crystals and foveal pseudocysts. Ophthalmic symptoms in SLS are reduced visual acuity and photophobia. This article reports the deficiency of macular pigment as a novel finding in this peculiar, congenital maculopathy. DESIGN: Cross-sectional, observational case study. PARTICIPANTS: Patients with clinically and genetically proven SLS. METHODS: Besides general ophthalmologic examination, 2 different methods were used, fundus autofluorescence (FAF) and fundus reflectometry with the macular pigment reflectometer (MPR), for measuring macular pigment (MP). MAIN OUTCOME MEASURES: Distribution profiles and quantity of MP in eyes of SLS patients. RESULTS: Twenty-eight eyes of 14 patients were included. The technique to measure MP depended on the ability of the mentally handicapped patients to cooperate. Fundus autofluorescence images providing qualitative estimates were obtained from 9 eyes of 5 patients, and MPR measures providing quantitative estimates were obtained from 19 eyes of 10 patients. Fundus autofluorescence images of SLS patients lacked the typical attenuation of macular FAF signal expected in normal eyes. Mean foveal MP levels measured by MPR showed significantly lower values in SLS patients (0.10+/-0.07) than in healthy individuals (0.69+/-0.17; P<0.001, Student t test). CONCLUSIONS: The group of SLS patients studied here had significantly reduced levels of foveal MP. The crystalline macular dystrophy in SLS seems to be the first known disease with a genetically caused deficiency of MP.

Autosomal dominant optic neuropathy and sensorineual hearing loss associated with a novel mutation of WFS1.

PURPOSE: To describe the phenotype of a novel Wolframin (WFS1) mutation in a family with autosomal dominant optic neuropathy and deafness. The study is designed as a retrospective observational case series. METHODS: Seven members of a Dutch family underwent ophthalmological, otological, and genetical examinations in one institution. Fasting serum glucose was assessed in the affected family members. RESULTS: All affected individuals showed loss of neuroretinal rim of the optic nerve at fundoscopy with enlarged blind spots at perimetry. They showed a red-green color vision defect at color vision tests and deviations at visually evoked response tests. The audiograms of the affected individuals showed hearing loss and were relatively flat. The unaffected individuals showed no visual deviations or hearing impairment. The affected family members had no glucose intolerance. Leber hereditary optic neuropathy (LHON) mitochondrial mutations and mutations in the Optic atrophy-1 gene (OPA1) were excluded. In the affected individuals, a novel missense mutation c.2508G>C (p.Lys836Asn) in exon 8 of WFS1 was identified. CONCLUSIONS: This study describes the phenotype of a family with autosomal dominant optic neuropathy and hearing impairment associated with a novel missense mutation in WFS1.

Clinical presentation and the presence of hearing impairment in branchio-oculo-facial syndrome: a new mutation in the TFAP2A gene.

We report on the clinical presentation of branchio-oculo-facial (BOF) syndrome in 2 patients with mutations in the TFAP2A gene (OMIM 107580). This TFAP2A gene was recently shown to be involved in the causation of BOF syndrome. An overview of the literature on BOF syndrome is given based on clinical reports written in the period during which mutation analysis was not yet available for BOF syndrome. We also give descriptions of the mutations in the TFAP2A gene in our 2 new patients with BOF syndrome. Congenital conductive hearing impairments are described, including hearing rehabilitation and the results of ear surgery.

ARSACS in the Dutch population: a frequent cause of early-onset cerebellar ataxia.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS: MIM 270550) is a neurodegenerative disorder characterized by early-onset cerebellar ataxia with spasticity and peripheral neuropathy. This disorder, considered to be rare, was first described in the late seventies among French Canadians in the isolated Charlevoix-Saguenay region of Quebec. Nowadays, it is known that the disorder is not only limited to this region but occurs worldwide. Our objective was to identify cases of autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) in Dutch patients with recessive early-onset cerebellar ataxia by sequencing the complete SACS gene. In a Dutch cohort of 43 index patients with ataxia onset before age 25, we identified 16 index patients (total 23 patients) with mutations in the SACS gene. Nine of them had homozygous mutations, and seven of them had compound heterozygous mutations. Retrospectively, the phenotype of patients carrying mutations was remarkably uniform: cerebellar ataxia with onset before age 13 years, lower limb spasticity and sensorimotor axonal neuropathy, and cerebellar (vermis) atrophy on magnetic resonance imaging, consistent with the core ARSACS phenotype previously described. The high rate of mutations (37%) identified in this cohort of Dutch patients suggests that ARSACS is substantially more frequent than previously estimated. We predict that the availability of SACS mutation analysis as well as an increasing awareness of the characteristic ARSACS phenotype will lead to the diagnosis of many additional patients, possibly even at a younger age.

Subclinical changes in the juvenile crystalline macular dystrophy in Sjögren-Larsson syndrome detected by optical coherence tomography.

PURPOSE: To study morphologic changes in the macula by optical coherence tomography (OCT) in patients with a crystalline macular dystrophy due to the autosomal recessive neurocutaneous Sjögren-Larsson syndrome (SLS). DESIGN: Retrospective observational case series. PARTICIPANTS: Twenty-seven eyes of 14 patients, mean age 14.6 (range, 3-24) years, with biochemically and genetically proven SLS underwent clinical and OCT investigation between September 2004 and September 2006. METHODS: All patients underwent full ophthalmologic examination including slit-lamp biomicroscopy and binocular ophthalmoscopy. Optical coherence tomography of all eyes was performed using the macular thickness map protocol of Stratus OCT. MAIN OUTCOME MEASURES: Macular morphology in clinical examination and OCT. RESULTS: Beside clinically visible perimacular crystalline deposits in all eyes of all study participants, macular morphology and reflectivity were significantly changed on OCT compared with healthy eyes. We found focal hyperreflectivities in all study eyes within the perifoveal ganglion cell layer and the inner plexiform layer, corresponding to the clinical localization of retinal crystals. More interestingly, a cystoid foveal degeneration on OCT was present in the majority of patients with SLS (18/27 eyes, or 67% of all eyes studied), varying from multiple microcystoid spaces to cystoid foveal atrophy. In general, patients who were severely affected on OCT showed intense changes on previously performed cerebral magnetic resonance spectroscopy. CONCLUSIONS: Patients with SLS show a childhood-onset crystalline macular dystrophy with cystoid foveal atrophy on OCT in most cases. The intraretinal deposition of lipid metabolites may lead to Müller cell degeneration with subsequent formation of cystoid spaces or atrophic changes within the fovea. Because this macular dystrophy is present in all examined patients with SLS, familiarity with this maculopathy seems important for the diagnosis of this rare systemic disease.

Phenotype description of a novel DFNA9/COCH mutation, I109T.

OBJECTIVES: This is a report of the audiological and vestibular characteristics of a Dutch DFNA9 family with a novel mutation, I109T, in the LCCL domain of COCH. METHODS: From the family with the novel I109T COCH mutation, audiometric data were collected and analyzed longitudinally. Results were compared to those obtained in previously identified P51 S, G88E, and G87W COCH mutation carriers. Special attention was also given to a comparison of age-related features such as progressive hearing loss and vestibular impairment. RESULTS: A novel mutation (I109T) in COCH segregates with hearing impairment and vestibular dysfunction in the present family. Pure tone thresholds, phoneme recognition scores, and vestibular responses of the I109T mutation carriers were essentially similar to those previously established in P51S, G87W, and G88E mutation carriers. Deterioration of hearing in the I109T mutation carriers started at 43 years of age, and vestibular function deteriorated at least 7 years later. CONCLUSIONS: The phenotype associated with the novel COCH (I109T) mutation is largely similar to that associated with P51S and G88E mutation carriers. However, subtle differences in terms of onset age and rate of progression seem to exist.

Vertical corneal striae in families with autosomal dominant hearing loss: DFNA9/COCH.

PURPOSE: Investigation of a possible association between vertical corneal striae and mutations in the COCH gene, observed in four DFNA9 families with autosomal dominant hearing loss and vestibular dysfunction. DESIGN: Prospective case series. METHODS: Ophthalmologic examinations with photography of the cornea after instillation of fluorescein were performed in 98 family members with 61 mutation carriers of four DFNA9 families at the Radboud University Nijmegen Medical Centre. Families 1 and 2 harbor the Pro51Ser mutation, and families 3 and 4 harbor the Gly88Glu and the Gly87Trp mutation, respectively. Statistical analysis was performed to find an association between the vertical corneal striae and the COCH mutation for each family and to test whether the four families were different in this respect. RESULTS: The vertical corneal striae were exclusively visible after instillation of fluorescein. They caused minor problems, as dry eye symptoms, and were not present in the general Dutch ophthalmologic population. The striae were present from an age of 47 years in 32 individuals, of whom 27 individuals had a COCH mutation. Statistical analysis on the striae and the COCH mutations showed a significant association in families 1, 2, and 3 (P = .0006), but not in family 4 (P = .63). CONCLUSIONS: Data analysis demonstrated a significant association between vertical corneal striae and the Pro51Ser and Gly88Glu mutations in the COCH gene in DFNA9 families 1, 2, and 3 with cochleovestibular dysfunction. Our findings suggest that the vertical corneal striae and cochleovestibular dysfunction may be caused by the same COCH mutations.

Cochleovestibular and ocular features in a Dutch DFNA11 family.

OBJECTIVES: To report hearing impairment and vestibular and ocular features in a Dutch DFNA11 family and to compare these results to reported data on three other DFNA11 families. STUDY DESIGN: Family study. METHODS: Regression analysis was performed in relation to age to outline the development of hearing thresholds and speech recognition scores. Vestibular and ocular functions were examined. RESULTS: First symptoms of hearing impairment started between the ages of 4 and 43 years. Most of the audiograms were symmetric and flat or downsloping. The annual threshold deterioration increased from 0.2 to 2.6 dB per year at 0.25 to 8 kHz in the longitudinal analyses and in the cross-sectional analysis from 0.3 to 0.9 dB per year. The speech recognition score was quite good, deteriorating by 0.9% per year from a 90% score at the age of 36 years onward. Remarkably, extensive ocular examination including corrected visual acuity and refraction measurements, slit-lamp examination, ophthalmoscopy, Goldmann perimetry, electroretinography and electro-oculography revealed signs of subclinical retinal dysfunction. None of the patients showed the classic triad of retinitis pigmentosa. Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers were fairly similar to previously described DFNA11 families. CONCLUSION: Even though the diverse mutations are located in different regions of the myosin VIIa gene, the cochleovestibular phenotype is fairly similar in all DFNA11 families. Surprisingly, only in this family was subclinical retinal dysfunction detected.

Congenital cataract facial dysmorphism neuropathy syndrome: a clinically recognizable entity.

Congenital cataracts facial dysmorphism neuropathy syndrome is a recently delineated autosomal recessive condition exclusively found in the Gypsy population. Congenital cataracts facial dysmorphism neuropathy syndrome is caused by a homozygous mutation in the CTDP1 gene, leading to disruption of the ribonucleic acid transcription machinery. This report presents a young Gypsy female affected by this rare disorder. Electromyography and sural nerve histology were in accordance with a hypomyelinating neuropathy. After clinical recognition of congenital cataracts facial dysmorphism neuropathy syndrome some years ago, we recently demonstrated the presence of the homozygous IVS6+389C-->T mutation in the CTDP1 gene in this family.