Intrafamilial Phenotypic Heterogeneity Research Articles

Woodhouse-Sakati syndrome: genotype–phenotype review and case of intra-familial heterogeneity

Woodhouse-Sakati syndrome (WSS) is a rare eponymous disease described by Drs. Woodhouse and Sakati in 1983 as a syndrome of hypogonadism, alopecia, diabetes mellitus, intellectual disability, and ECG abnormalities. A couple of years later, a variant in the gene DCAF17 (DDB1 and CUL4-associated factor 17) was labeled as the founder mutation in most cases of WSS in the Arabian Peninsula and the Middle East. Reports around the world started to emerge on variable presentations of the syndrome, expanding its phenotypic spectrum. In addition, the discovery of new variants in the same gene grew our understanding of this multi-systemic syndrome. Genotype and phenotype expansion is increasing with the growing number of diagnosed cases owing to the availability and advances in clinical genetic testing. This review describes the current understanding of the DCAF17 gene with its molecular implication in WSS. We also provide an extensive analysis of the documented genetic changes associated with the syndrome, describing the geographical prevalence of these genetic variations. Additionally, we examine the disorder’s extensive manifestations and clinical presentations and describe a case of intra-familial phenotypic heterogeneity.

A Novel Variant of GCH1 in Dopa-Responsive Dystonia With Oculogyric Crises and Intrafamilial Phenotypic Heterogeneity.

A Novel Variant of GCH1 in Dopa-Responsive Dystonia With Oculogyric Crises and Intrafamilial Phenotypic Heterogeneity.

Comparative study of PRPH2 D2 loop mutants reveals divergent disease mechanism in rods and cones

Mutations in the photoreceptor-specific tetraspanin gene peripherin-2 (PRPH2) lead to widely varying forms of retinal degeneration ranging from retinitis pigmentosa to macular dystrophy. Both inter- and intra-familial phenotypic heterogeneity has led to much interest in uncovering the complex pathogenic mechanisms of PRPH2-associated disease. Majority of disease-causing mutations in PRPH2 reside in the second intradiscal loop, wherein seven cysteines control protein folding and oligomerization. Here, we utilize knockin models to evaluate the role of three D2 loop cysteine mutants (Y141C, C213Y and C150S), alone or in combination. We elucidated how these mutations affect PRPH2 properties, including oligomerization and subcellular localization, and contribute to disease processes. Results from our structural, functional and molecular studies revealed that, in contrast to our understanding from prior investigations, rods are highly affected by PRPH2 mutations interfering with oligomerization and not merely by the haploinsufficiency associated with these mutations. On the other hand, cones are less affected by the toxicity of the mutant protein and significantly reduced protein levels, suggesting that knockdown therapeutic strategies may sustain cone functionality for a longer period. This observation provides useful data to guide and simplify the current development of effective therapeutic approaches for PRPH2-associated diseases that combine knockdown with high levels of gene supplementation needed to generate prolonged rod improvement.

Intrafamilial and interfamilial heterogeneity of PINK1-associated Parkinson's disease in Sudan

PINK1 is the second most predominant gene associated with autosomal recessive Parkinson's disease. Homozygous mutations in this gene are associated with an early onset of symptoms. Bradykinesia, tremors, and rigidity are common features, while dystonia, motor fluctuation, and non-motor symptoms occur in a lower percentage of cases and usually respond well to levodopa. We investigated 14 individuals with parkinsonism and eleven symptom-free siblings from three consanguineous Sudanese families, two of them multigenerational, using a custom gene panel screening 34 genes, 27 risk variants, and 8 candidate genes associated with parkinsonism. We found a known pathogenic nonsense PINK1 variant (NM_032409.3:c.1366C>T; p.(Gln456*)), a novel pathogenic single base duplication (NM_032409.3:c.1597dup; p.(Gln533Profs*29)), and another novel pathogenic insertion (NM_032409.3:c.1448_1449ins[1429_1443; TTGAG]; p.(Arg483Serfs*7)). All variants were homozygous and co-segregated in all affected family members. We also identified intrafamilial and interfamilial phenotypic heterogeneity associated with PINK1 mutations in these Sudanese cases, possibly reflecting the nature of the Sudanese population that has a large effective population size, which suggests a higher possibility of novel findings in monogenic and polygenic diseases in Sudan.

Intra-familial phenotypic heterogeneity of m.3243A>G carriers remains elusive as long as heteroplasmy and mtDNA copy numbers are absent: reply.

Intra-familial phenotypic heterogeneity of m.3243A>G carriers remains elusive as long as heteroplasmy and mtDNA copy numbers are absent: reply.

Description of Phenotypic Heterogeneity in a GJC2-Related Family and Literature Review

Introduction: Homozygous and compound heterozygous variants in GJC2, the gene encoding connexin-47 protein, cause Pelizaeus-Merzbacher-like disease type 1 or hypomyelinating leukodystrophy 2 (HLD2), a severe infantile-onset hypomyelinating leukodystrophy, and rarely some milder phenotypes like hereditary spastic paraplegia (HSP) type 44 (SPG44) and subclinical leukodystrophy. Herein, we report an Iranian GJC2-related family with intrafamilial phenotypic heterogeneity and review the literatures. Methods: Whole-exome sequencing was performed for an Iranian proband, who was initially diagnosed as HSP case. Data were analyzed and the candidate variant was confirmed by PCR and Sanger sequencing subsequently checked in family members to co-segregation analysis. A careful clinical and paraclinical evaluation of all affected individuals of the family was done and compared with previous reported GJC2-related families. Results: A novel homozygous variant, c.G14T:p.Ser5Ile, in the GJC2 gene was identified. The variant was co-segregated with the disease status in the family members. Clinical evaluation of all patients showed two distinct GJC2-related phenotypes in this family; the proband presented a complicated form of HSP, whereas both his affected sisters presented a HLD2 phenotype. Discussion: Up to now, correlation between HSP and GJC2 variants has been reported once. Here, the second case of SPG44 was identified that emphasizes on GJC2 as a HSP-causing gene. So, the screening of GJC2 in patients with HSP or HSP-like phenotypes especially with hypomyelination in their brain MRI is recommended. Also, for the first time, intrafamilial phenotypic heterogeneity for “two distinct GJC2-related phenotypes: HLD2 and HSP” was reported. Such intrafamilial phenotypic heterogeneity for GJC2 can emphasize on the shared pathophysiology of these disorders.

Intra-familial phenotypic heterogeneity of m.3243A > G carriers remains elusive as long as heteroplasmy and mtDNA copy numbers are absent.

Intra-familial phenotypic heterogeneity of m.3243A > G carriers remains elusive as long as heteroplasmy and mtDNA copy numbers are absent.

A Novel Loss-of-function Mutation in MYBPC3 Causes Familial Hypertrophic Cardiomyopathy with Extreme Intrafamilial Phenotypic Heterogeneity.

Cardiomyopathies are a heterogeneous group of diseases predominantly affecting the heart muscle and often lead to progressive heart failure-related disability or cardiovascular death. Hypertrophic cardiomyopathy (HCM) is a cardiac muscle disorder mostly caused by the mutations in genes encoding cardiac sarcomere. Germ-line mutations in MYBPC3 causes hypertrophic cardiomyopathy (HCM). However, most of the HCM associated MYBPC3 mutations were truncating mutations. Extreme phenotypic heterogeneity was observed among HCM patients with MYBPC3 mutations. In this study, we investigated a Chinese man who presented with HCM. Whole exome sequencing identified a novel heterozygous deletion (c.3781_3785delGAGGC) in exon 33 of the MYBPC3 in the proband. This heterozygous variant causes frameshift (p.Glu1261Thrfs*3), which predicted to form a truncated MYBPC3 protein. The proband's father also carries this variant in a heterozygous state while the proband's mother did not harbor this variant. Here, we report on a novel deletion in the MYBPC3 gene associated with HCM. We also highlight the importance of whole exome sequencing for molecular diagnosis for the patients with familial HCM.

Identification of a new familial case of 3q29 deletion syndrome associated with cleft lip and palate via whole-exome sequencing.

Many unbalanced large copy number variants reviewed in the paper are associated with syndromic orofacial clefts, including a 1.6Mb deletion on chromosome 3q29. The current report presents a new family with this recurrent deletion identified via whole-exome sequencing and confirmed by array comparative genomic hybridization. The proband exhibited a more severe clinical phenotype than his affected mother, comprising right-sided cleft lip/alveolus and cleft palate, advanced dental caries, heart defect, hypospadias, psychomotor, and speech delay, and an intellectual disability. Data analysis from the 3q29 registry revealed that the 3q29 deletion increases the risk of clefting by nearly 30-fold. No additional rare and pathogenic nucleotide variants were identified that could explain the clefting phenotype and observed intrafamilial phenotypic heterogeneity. These data suggest that the 3q29 deletion may be the primary risk factor for clefting, with additional genomic variants located outside the coding sequences, methylation changes, or environmental exposure serving as modifiers of this risk. Additional studies, including whole-genome sequencing or methylation analyses, should be performed to identify genetic factors underlying the phenotypic variation associated with the recurrent 3q29 deletion.

Familial Bainbridge-Ropers syndrome: Report of familial ASXL3 inheritance and a milder phenotype.

De novo truncating and splicing pathogenic variants in the Additional Sex Combs-Like 3 (ASXL3) gene are known to cause neurodevelopmental delay, intellectual disability, behavioral difficulties, hypotonia, feeding problems and characteristic facial features. We previously reported 45 patients with ASXL3-related disorder including three individuals with a familial variant. Here we report the detailed clinical and molecular characteristics of these three families with inherited ASXL3-related disorder. First, a father and son with c.2791_2792del p.Gln931fs pathogenic variant. The second, a mother, daughter and son with c.4534C > T, p.Gln1512Ter pathogenic variant. The third, a mother and her daughter with c.4441dup, p.Leu1481fs maternally inherited pathogenic variant. This report demonstrates intrafamilial phenotypic heterogeneity and confirms heritability of ASXL3-related disorder.

A Novel Frame-Shift Mutation in SCNN1B Identified in a Chinese Family Characterized by Early-Onset Hypertension.

BackgroundLiddle syndrome is a form of monogenic hypertension caused by mutations in the three homologous subunits of the epithelial sodium channels (ENaCs), α, β, and γ. It is characterized by early-onset refractory hypertension, hypokalemia, low renin activity, and hypoaldosteronism. In this study, we report a novel frame-shift mutation in SCNN1B responsible for Liddle syndrome in a Chinese family.MethodsDNA samples were collected from all participants. Whole-exome sequencing was performed in the proband to detect possible causative variants. Sanger sequencing was then conducted in the other family members to verify the candidate variant, and in 100 patients with hypertension and 100 normotensive controls to exclude population genetic polymorphism.ResultsWe identified a novel frame-shift mutation (c.1691_1693delinsG) in SCNN1B that was responsible for Liddle syndrome in this family. This mutation leads to the substitution of Arg in place of Gln at codon site 564 and generates a new stop codon at 592, influencing the crucial PY motif and resulting in reduced inactivation of the ENaCs. Aside from the proband, eight family members carried the mutation. Intra-familial phenotypic heterogeneity was observed in the blood pressure and serum potassium levels. Amiloride therapy combined with a low sodium diet is effective to alleviate the symptoms of patients with Liddle syndrome.Conclusionc.1691_1693delinsG, a novel frame-shift mutation in the β subunit of ENaC, was identified in a Chinese family with Liddle syndrome by whole-exome sequencing. Phenotypic heterogeneity can make diagnosis of Liddle syndrome difficult on the basis of clinical or biochemical characteristics alone. Genetic analysis is a useful tool allowing timely and accurate diagnosis of Liddle syndrome and playing a guiding role in precise treatment of the disease.

Mutational and clinical spectrum of Japanese patients with hereditary hemorrhagic telangiectasia

BackgroundHereditary hemorrhagic telangiectasia (HHT) is a dominantly inherited vascular disorder characterized by recurrent epistaxis, skin/mucocutaneous telangiectasia, and organ/visceral arteriovenous malformations (AVM). HHT is mostly caused by mutations either in the ENG or ACVRL1 genes, and there are regional differences in the breakdown of causative genes. The clinical presentation is also variable between populations suggesting the influence of environmental or genetic backgrounds. In this study, we report the largest series of mutational and clinical analyses for East Asians.MethodsUsing DNAs derived from peripheral blood leukocytes of 281 Japanese HHT patients from 150 families, all exons and exon–intron boundaries of the ENG, ACVRL1, and SMAD4 genes were sequenced either by Sanger sequencing or by the next-generation sequencing. Deletions/amplifications were analyzed by the multiplex ligation-dependent probe amplification analyses. Clinical information was obtained by chart review.ResultsIn total, 80 and 59 pathogenic/likely pathogenic variants were identified in the ENG and ACVRL1 genes, respectively. No pathogenic variants were identified in the SMAD4 gene. In the ENG gene, the majority (60/80) of the pathogenic variants were private mutations unique to a single family, and the variants were widely distributed without any distinct hot spots. In the ACVRL1 gene, the variants were more commonly found in exons 5–10 which encompasses the serine/threonine kinase domain. Of these, 25/59 variants were unique to a single family while those in exons 8–10 tended to be shared by multiple (2–7) families. Pulmonary and cerebral AVMs were more commonly found in ENG-HHT (69.1 vs. 14.4%, 34.0 vs. 5.2%) while hepatic AVM was more common in ACVRL1-HHT (31.5 vs. 73.2%). Notable differences include an increased incidence of cerebral (34.0% in ENG-HHT and 5.2% in ACVRL1-HHT), spinal (2.5% in ENG-HHT and 1.0% in ACVL1-HHT), and gastric AVM (13.0% in ENG-HHT, 26.8% in ACVRL1-HHT) in our cohort. Intrafamilial phenotypic heterogeneity not related to the age of examination was observed in 71.4% and 24.1% of ENG- and ACVRL1-HHT, respectively.ConclusionsIn a large Japanese cohort, ENG-HHT was 1.35 times more common than ACVRL1-HHT. The phenotypic presentations were similar to the previous reports although the cerebral, spinal, and gastric AVMs were more common.

Demographic, clinical, and ancestry characterization of a large cluster of mucopolysaccharidosis IV A in the Brazilian Northeast region.

Mucopolysaccharidosis (MPS) IVA is a rare autosomal recessive disease with a highly variable distribution worldwide. Discrepancies in the incidence of MPS IVA among populations of different ethnicities are mostly attributed to founder effects. Demographic and clinical data from 28 MPS IVA patients, followed at a single center, and ancestry (Y chromosome and mitochondrial markers) of a subsample of 17 patients, most with the p.Ser341Arg (c.1023C>G) mutation were analyzed. Parental consanguinity was observed in 15/20 couples; a rare homozygous N-acetylgalactosamine-6-sulfatase (GALNS) mutation was found in 7/16 families with intra-familial phenotypic heterogeneity. Paternal ancestry was 94.2% (16/17) European, 5.8% (1/17) African, and 0% Amerindian. The European paternal haplogroups R1a, R1b, and R* accounted for 94.2% (16/17) of the patients. The R1b haplogroup, identified in 59% (10/17) of the patients, is frequently found in populations from the Iberian Peninsula. European, Amerindian, and African maternal ancestry was observed in 46.9% (8/17), 35.4% (6/17), and 17.7% (3/17) of the patients, respectively. Study of a cluster of MPS IVA patients from Northeastern Brazil, with high parental consanguinity and phenotypic heterogeneity showed predominantly European parental ancestry. This ancestry finding corroborates historical data on the local settlement, formed predominantly by European men.

Intrafamilial phenotypic heterogeneity related to a new DMD splice site variant

Dystrophinopathies are a group of X-linked neuromuscular disorders that result from pathogenic variants in the DMD gene. Their pathophysiological substrate is the defective expression of dystrophin in many tissues. While patients from the same pedigree usually present similar dystrophin expression and clinical course, the extent of cardiac and skeletal muscle involvement may not correlate in the same individual. We identified a new splice site variant c.2803+5G>C (NM_004006) ClinVar VCV000803902, located in intron 22 of DMD in a Brazilian family that present a broad phenotypic and histological heterogeneity. One of the subjects had a typical Duchenne muscular dystrophy (DMD) phenotype, whereas the others had Becker muscular dystrophy (BMD). Cardiac involvement was remarkable in some of the BMD patients, but not in the DMD patient. Western blot analysis of skeletal muscle revealed much lower levels of calsequestrin in the most severely affected patient compared to his brother, whose phenotype is BMD, highlighting the potential role of proteins involved in skeletal muscle calcium homeostasis in differential degrees of dystrophinopathies.

Genetic mosaicism, intrafamilial phenotypic heterogeneity, and molecular defects of a novel missense SLC6A1 mutation associated with epilepsy and ADHD

BackgroundMutations in SLC6A1, encoding γ-aminobutyric acid (GABA) transporter 1 (GAT-1), have been recently associated with a spectrum of neurodevelopmental disorders ranging from variable epilepsy syndromes, intellectual disability (ID), autism and others. To date, most identified mutations are de novo. We here report a pedigree of two siblings associated with myoclonic astatic epilepsy, attention deficit hyperactivity disorder (ADHD), and ID. MethodsNext-generation sequencing identified a missense mutation in the SLC6A1 gene (c.373G > A(p.Val125Met)) in the sisters but not in their shared mother who is also asymptomatic, suggesting gonadal mosaicism. We have thoroughly characterized the clinical phenotypes: EEG recordings identified features for absence seizures and prominent bursts of occipital intermittent rhythmic delta activity (OIRDA). The molecular pathophysiology underlying the clinical phenotypes was assessed using a multidisciplinary approach including machine learning, confocal microscopy, and high-throughput 3H radio-labeled GABA uptake assays in mouse astrocytes and neurons. ResultsThe GAT-1(Val125Met) mutation destabilizes the global protein conformation and reduces transporter protein expression at total and cell surface. The mutant transporter protein was localized intracellularly inside the endoplasmic reticulum (ER) in both HEK293T cells and astrocytes which may directly contribute to seizures in patients. Radioactive 3H-labeled GABA uptake assay indicated the mutation reduced the function of the mutant GAT-1(Val125Met) to ~30% of the wildtype. ConclusionsThe seizure phenotypes, ADHD, and impaired cognition are likely caused by a partial loss-of-function of GAT-1 due to protein destabilization resulting from the mutation. Reduced GAT-1 function in astrocytes and neurons may consequently alter brain network activities such as increased seizures and reduced attention.

A novel loss-of-function mutation in LACC1 underlies hereditary juvenile arthritis with extended intra-familial phenotypic heterogeneity.

To investigate phenotypic and molecular characteristics of a consanguineous family with autosomal-recessive, polyarticular, juvenile isiopathic arthriris (JIA) with extra-articular manifestations, including renal amyloidosis and Crohn's disease, associated with a novel homozygous truncating variant in LACC1. Whole exome sequencing (WES) or targeted Sanger verification were performed in 15 participants. LACC1 expression and cytokine array were analysed in patient-derived and CRISPR/Cas9-generated LACC1-knockout macrophages (Mϕ). A homozygous truncating variant (p.Glu348Ter) in LACC1 was identified in three affected and one asymptomatic family member, and predicted harmful by causing premature stop of the LACC1 protein sequences, and by absence from ethnically-matched controls and public variation databases. Expression studies in patient-derived macrophages (Mϕ) showed no endogenous p.Glu348Ter-LACC1 RNA transcription or protein expression, compatible with nonsense-mediated mRNA decay. WES analysis in the asymptomatic homozygous subject for p. Glu348Ter-LACC1 detected an exclusive heterozygous variant (p.Arg928Gln) in complement component C5. Further complement activity analysis suggested a protective role for the p.Arg928Gln-C5 variant as a phenotypic modifier of LACC1-associated disease. Finally, cytokine profile analysis indicated increased levels of pro-inflammatory cytokines in LACC1-disrupted as compared with wild-type Mϕ. Our findings reinforce the role of LACC1 disruption in autosomal-recessive JIA, extend the clinical spectrum and intra-familial heterogeneity of the disease-associated phenotype, indicate a modulatory effect of complement factor C5 on phenotypic severity, and suggest an inhibitory role for wild-type LACC1 on pro-inflammatory pathways.

ROM1 contributes to phenotypic heterogeneity in PRPH2-associated retinal disease.

Peripherin 2 (PRPH2) is a retina-specific tetraspanin protein essential for the formation of rod and cone photoreceptor outer segments (OS). Patients with mutations in PRPH2 exhibit severe retinal degeneration characterized by vast inter- and intra-familial phenotypic heterogeneity. To help understand contributors to this within-mutation disease variability, we asked whether the PRPH2 binding partner rod OS membrane protein 1 (ROM1) could serve as a phenotypic modifier. We utilized knockin and transgenic mouse models to evaluate the structural, functional and biochemical effects of eliminating one allele of Rom1 (Rom1+/-) in three different Prph2 models which mimic human disease: C213Y Prph2 (Prph2C/+), K153Del Prph2 (Prph2K/+) and R172W (Prph2R172W). Reducing Rom1 in the absence of Prph2 mutations (Rom1+/-) had no effect on retinal structure or function. However, the effects of reducing Rom1 in the presence of Prph2 mutations were highly variable. Prph2K/+/Rom1+/- mice had improved rod and cone function compared with Prph2K/+ as well as amelioration of K153Del-associated defects in PRPH2/ROM1 oligomerization. In contrast, Prph2R172W/Rom1+/- animals had worsened rod and cone function and exacerbated retinal degeneration compared with Prph2R172W animals. Removing one allele of Rom1 had no effect in Prph2C/+. Combined, our findings support a role for non-pathogenic ROM1 null variants in contributing to phenotypic variability in mutant PRPH2-associated retinal degeneration. Since the effects of Rom1 reduction are variable, our data suggest that this contribution is specific to the type of Prph2 mutation.

Reply to: Double Trouble from POLG1 and CLCN1 Variants with Intrafamilial Phenotypic Heterogeneity.

Reply to: Double Trouble from POLG1 and CLCN1 Variants with Intrafamilial Phenotypic Heterogeneity.

Double Trouble from POLG1 and CLCN1 Variants with Intrafamilial Phenotypic Heterogeneity.

I read with interest the article by Pauly and colleagues1 about a family in which the father carried the variants c.844T>G in POLG1 and c.937G>A in CLCN1. The POLG1 variant manifested with ptosis, ophthalmoparesis, parkinsonism, and depression, and the CLCN1 variant with myotonia (myoclonic twitches and muscle cramping triggered by rapid movements or sneezing) and muscle hypertrophy.1 All of his 3 children carried his POLG1 variant and 1 the CLCN1 variant, but only 2 manifested clinically.1 The study has a number of shortcomings. Missing are the results of cerebral magnetic resonance imaging and the electroencephalogram. “Twitching” and “cramping” may not only be attributable to the CLCN1 variant but also to the POLG1 variant.2 POLG1 variants may manifest with myoclonic epilepsy, which needs to be excluded as it requires a completely different therapy. This is of relevance as the deceased daughter had Alpers-Huttenlocher disease, thus intractable epilepsy. Because “twitching” was triggerable,1 we should know if the clinical phenomenon correlated with the occurrence of myotonic discharges on needle electromyography. Because the father and his son both had myopathy of the extraocular eye muscles and POLG1 variants can also manifest with myopathy of the skeletal muscles,3 we should know if the father or his son had undergone muscle biopsy to see if features for a mitochondrial disorder (MID) were present or not. Missing are results of mitochondrial DNA (mtDNA) investigations. Because POLG1 variants may secondarily cause mtDNA depletion or multiple mtDNA deletions,4 we should know if the amount of mtDNA was reduced or if there were multiple mtDNA deletions. There is no explanation provided why the second girl did not manifest clinically from the POLG1 variant. Because MIDs frequently manifest subclinically, we should know if the girl was investigated for subclinical involvement of the brain, eyes, ears, endocrine organs, heart, intestines, or kidneys. Early detection of clinical manifestations is crucial as early treatment may improve the outcome in these patients. Assuming that the girl did not even manifest subclinically, the missing penetrance of the variant should be explained. It is conceivable that secondary damage of mtDNA was not present in this girl but only in her sister and brother. It is also not discussed why the mother of the 3 children who carried the POLG1 variant c.1399GA>A did not manifest clinically. Cardiac complications may not only derive from the CLCN1 variant but also from the POLG1 variant.5 Because cardiac involvement in MIDs strongly determines the outcome of these patients, it is crucial that they undergo regular follow-up investigations and long-term electrocardiogram recordings. If ventricular arrhythmias are recorded, implantation of an implantable cardioverter-defibrillator may strongly improve the survival and outcome of these patients. Cardiac surveillance is crucial in the light of the side effects of flecainide. It should be mentioned that, among the syndromic MIDs, POLG1 variants can also cause Leigh syndrome; mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes; myoclonic epilepsy with ragged-red fibers; myoclonic epilepsy myopathy sensory ataxia; sensory ataxic neuropathy, dysarthria, ophthalmoparesis; and chronic progressive external ophthalmoplegia syndrome. Overall, this study has a number of shortcomings that should be addressed and considered for modifying the conclusions. Genetic findings need to be related to the clinical presentation, and factors determining phenotypic variability need to be discussed. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Informed patient consent and the approval of an institutional review board was not necessary for this work. There are no conflicts of interest and no funding was received for this work. There are no disclosures to report.

Comprehensive Geno- and Phenotyping in a Complex Pedigree Including Four Different Inherited Retinal Dystrophies.

Inherited retinal dystrophies (IRDs) are characterized by high clinical and genetic heterogeneity. A precise characterization is desirable for diagnosis and has impact on prognosis, patient counseling, and potential therapeutic options. Here, we demonstrate the effectiveness of the combination of in-depth retinal phenotyping and molecular genetic testing in complex pedigrees with different IRDs. Four affected Caucasians and two unaffected relatives were characterized including multimodal retinal imaging, functional testing, and targeted next-generation sequencing. A considerable intrafamilial phenotypic and genotypic heterogeneity was identified. While the parents of the index family presented with rod-cone dystrophy and ABCA4-related retinopathy, their two sons revealed characteristics in the spectrum of incomplete congenital stationary night blindness and ocular albinism, respectively. Molecular testing revealed previously described variants in RHO, ABCA4, and MITF as well as a novel variant in CACNA1F. Identified variants were verified by intrafamilial co-segregation, bioinformatic annotations, and in silico analysis. The coexistence of four independent IRDs caused by distinct mutations and inheritance modes in one pedigree is demonstrated. These findings highlight the complexity of IRDs and underscore the need for the combination of extensive molecular genetic testing and clinical characterization. In addition, a novel variant in the CACNA1F gene is reported associated with incomplete congenital stationary night blindness.