Identification of a novel LMX1B nonsense variant associated with congenital talipes equinovarus by prenatal exome sequencing: A case report.

BACKGROUND: Congenital talipes equinovarus (CTEV) is a rotational foot deformity that affects muscles, bones, connective tissue, and vascular or neurological tissues. The etiology of CTEV is complex and unclear, involving genetic and environmental factors. Nail-patella syndrome is an autosomal dominant disorder caused by variants of the LIM homeobox transcription factor 1 beta gene (LMX1B, OMIM:602575). LMX1B plays a key role in the development of dorsal limb structures, the kidneys, and the eyes, and variants in this gene may manifest as hypoplastic or absent patella, dystrophic nails, and elbow and iliac horn dysplasia; glomerulopathy; and adult-onset glaucoma, respectively. This study aimed to identify pathogenic variants in a fetus with isolated talipes equinovarus diagnosed by ultrasound in the second trimester, whose father exhibited dysplastic nails and congenital absence of bilateral patella. METHODS: Prenatal whole-exome sequencing (WES) of the fetus and parents was performed to identify the genetic variant responsible for the fetal ultrasound abnormality, followed by validation using Sanger sequencing. RESULTS: A novel heterozygous nonsense variant in exon 6 of LMX1B (c.844C>T, p.Gln282*) was identified in the fetus and the affected father but was not detected in any unaffected family members. This nonsense variant resulted in a premature termination codon at position 282, which may be responsible for the clinical phenotype through the loss of function of the gene product. CONCLUSIONS: Our study indicating that a fetus carrying a novel nonsense variant of LMX1B (c.844C>T, p.Gln282*) can exhibit isolated talipes equinovarus, which expands the LMX1B genotypic spectrum and is advantageous for genetic counseling.

Simultaneous kidney and pancreas transplantation in a patient with nail-patella syndrome and insulin-dependent diabetes.

BACKGROUND: Nail-patella syndrome (NPS) is a rare autosomal dominant disorder caused by a mutation in LIM-homeodomain transcription factor 1-beta (LMX1B) and characterized by nail dystrophy, skeletal changes, glaucoma, and kidney disease with up to 30% of patients progressing to kidney failure. Autoimmune diseases, including thyroid disease, have been reported previously in patients with NPS. CASE-DIAGNOSIS/TREATMENT: We report the case of a pediatric patient with NPS with kidney failure, hypothyroidism, and type 1 diabetes mellitus. The patient's pedigree and identification of a kidney specific mutation in LMX1B was a result of whole exome sequencing. Clinical data was obtained from retrospective chart review and included the 1-year post-transplant follow-up period. At 15 years of age, our patient received a simultaneous kidney-pancreas transplantation, from a 3 HLA antigen mismatched deceased donor. The donor was CMV + , EBV - and our patient was CMV - , EBV - at time of transplant. Our patient maintained normal kidney function and euglycemia without insulin therapy at 1 year post-transplant. CONCLUSIONS: The patient's hypothyroidism, diabetes mellitus, and kidney failure may all be related to LMX1B mutation. Further study is needed to clarify the genetic link between these processes. Simultaneous kidney-pancreas transplantation can be used to successfully treat diabetes mellitus and kidney failure in a pediatric patient.

Case Report: Inversion of LMX1B - A Novel Cause of Nail-Patella Syndrome in a Swedish Family and a Longtime Follow-Up.

Nail-patella syndrome (NPS, OMIM #161200) is a rare autosomal dominant disorder with symptoms from many different parts of the body, including nails, knees, elbows, pelvis, kidneys and eyes. It is caused by truncating variants in the LMX1B gene, which encodes a transcription factor with important roles during embryonic development, including dorsoventral patterning of the limbs. To our knowledge, inversions disrupting the LMX1B gene have not been reported. Here, we report a family with an inversion disrupting the LMX1B gene in five affected family members with mild but variable clinical features of NPS. Our finding demonstrates that genomic rearrangements must be considered a possible cause of NPS.

A Novel LMX1B Variant Identified in a Patient Presenting with Severe Renal Involvement and Thin Glomerular Basement Membrane.

We report a case of nail-patella syndrome (NPS) with unusual thinning of the glomerular basement membrane (GBM) associated with a novel heterozygous variant in the LMX1B gene. A 43-year-old female patient with a previous diagnosis of NPS, referred to our hospital for persistent proteinuria, underwent a renal biopsy, which revealed minor glomerular abnormalities. She underwent a second renal biopsy at the age of 56 owing to the presence of persistent proteinuria and decline in serum albumin, meeting the diagnostic criteria for nephrotic syndrome. Light microscopy demonstrated glomerulosclerosis and cystic dilatation of the renal tubules. Notably, electron microscopy revealed unusual thinning of the GBM, which is quite different from typical biopsy findings observed in patients with NPS, characterized by thick GBM with fibrillary material and electron-lucent structures. Comprehensive genetic screening for 168 known genes responsible for inherited kidney diseases using a next-generation sequencing panel identified a novel heterozygous in-frame deletion-insertion (c.723_729delinsCAAC: p.[Ser242_Lys243delinsAsn]) in exon 4 of the LMX1B gene, which may account for the disrupted GBM structure. Further studies are warranted to elucidate the complex genotype-phenotype relationship between LMX1B and proper GBM morphogenesis.

Peters Anomaly in Nail-Patella Syndrome: A Case Report and Clinico-Genetic Correlation.

PURPOSE: The purpose of this study was to report the clinicopathological features of Peters anomaly in a child with nail-patella syndrome. METHODS: Nail-patella syndrome (NPS) is a rare autosomal dominant connective tissue disorder characterized by several anomalies of the extremities, joints and nails, glomerulopathy, and rarely ocular involvement. NPS is caused by heterozygous loss-of-functional mutations in the LMX1B gene that encodes the LIM homeodomain proteins. RESULTS: This case reports a new association of Peters anomaly in a child with NPS that also had classic skeletal/nail anomalies and protein losing nephropathy. Furthermore, DNA sequence analysis identified a novel missense heterozygous mutation in the LMX1B gene (Transcript ID: NM_001174146) resulting in the replacement of tryptophan by serine in codon 266, suggesting that the mutation (p.Trp.266Ser) affects LMX1B function by disturbing its interactions with other proteins. To the best of our knowledge, this association of Peters anomaly is novel and has not been reported earlier in the ophthalmic and systemic literature on NPS. CONCLUSION: The corneal findings in our case with NPS are similar to those seen in congenital corneal opacification because of Peters anomaly. This novel association of Peters anomaly with NPS may be related to the effects of the LMX1B mutation on corneal development.

Diagnosing nail-patella syndrome: can it be so simple?

We describe here an interesting case of a 7-day-old male infant brought with parental concerns of inability to extend both knees. Clinical evaluation revealed dysplastic fingernails, bilateral abnormal patellae, triangular lunules in conjunction with pathognomic iliac horns on pelvic radiographs suggesting the possibility of nail-patella syndrome (NPS). Other competing diagnoses with similar phenotypic features were considered and sequentially excluded. A definitive diagnosis was established by the identification of the principal mutation at the LMX1B gene locus of chromosome 9. NPS is seldom diagnosed in neonates due to the heterogeneity of clinical presentations as well as the subtlety of clinical clues in this population. NPS is a dominantly inherited disorder that is predominantly familial in origin and thus carries important implications for the prenatal diagnosis of future pregnancies as well as pre-emptive surveillance of nephropathy in the index child.

A rare disorder causing chronic joint pain in an adolescent.

ABSTRACT: This article describes a patient with chronic knee pain and deformities of her hands and feet that led to a diagnosis of nail-patella syndrome, a rare autosomal dominant disorder.

[Prenatal diagnosis and pedigree analysis of a case of Nail-patella syndrome].

OBJECTIVE: To carried out prenatal diagnosis and genetic analysis for a case with Nail-patella syndrome. METHODS: Based on the clinical phenotype and prenatal imaging, genetic testing and prenatal diagnosis were carried out through whole exome sequencing (WES) and Sanger sequencing. RESULTS: Analysis of amniotic fluid showed that the fetus has carried a heterozygous c.139+1G>T splicing site variant [Chr9(GRCh37): g.129376868G>T] of the LMX1B gene, which was verified by Sanger sequencing. The same heterozygous variant was found in the pregnant woman, her daughter and her mother but not in her husband. Searching of HGMD database showed that the c.139+1G>T was previously unreported. CONCLUSION: Nail-patella syndrome is an autosomal dominant genetic disorder with various clinical manifestations. WES is helpful for its genetic and prenatal diagnosis.

Nail-patella syndrome: "nailing" the diagnosis in three generations.

Nail-patella syndrome (NPS) is a hereditary disorder characterized by fingernail changes, elbow dysplasia, hypoplastic patellae, and presence of iliac horns. Clinical presentation can be subtle, and the spectrum of presentation often makes NPS a challenging diagnosis. Herein, we describe three family members with nail-patella syndrome who presented with different features and varying severity. The opportunity to recognize this rare syndrome in three linear generations provided a unique insight into NPS, and a moment to appreciate the random and unpredictable clinical presentation.

Paroxysmal Cranial Dyskinesia and Nail-Patella Syndrome Caused by a Novel Variant in the LMX1B Gene.

BACKGROUND: In a Danish family, multiple individuals in five generations present with early-onset paroxysmal cranial dyskinesia, musculoskeletal abnormalities, and kidney dysfunction. OBJECTIVE: To demonstrate linkage and to identify the underlying genetic cause of disease. METHODS: Genome-wide single-nucleotide polymorphisms analysis, Sequence-Tagged-Site marker analyses, exome sequencing, and Sanger sequencing were performed. RESULTS: Linkage analyses identified a candidate locus on chromosome 9. Exome sequencing revealed a novel variant in LMX1B present in all affected individuals, logarithm of the odds (LOD) score of z = 6.54, predicted to be damaging. Nail-patella syndrome (NPS) is caused by pathogenic variants in LMX1B encoding a transcription factor essential to cytoskeletal and kidney growth and dopaminergic and serotonergic network development. NPS is characterized by abnormal musculoskeletal features and kidney dysfunction. Movement disorders have not previously been associated with NPS. CONCLUSIONS: Paroxysmal dyskinesia is a heretofore unrecognized feature of the NPS spectrum. The pathogenic mechanism might relate to aberrant dopaminergic circuits. © 2020 International Parkinson and Movement Disorder Society.

A novel mutation in LMX1B gene in a newborn with nail-patella syndrome: Clinical and dermoscopic findings.

We report on a 3-month-old female patient presenting with bilateral anonychia of the thumbnails and hyponychia of the index nails. Clinico-dermoscopic examination revealed triangular lunulae in all fingernails. Sequence analysis of LMX1B gene identified a novel heterozygous de novo mutation within exon 2, pathogenetic for a nail-patella syndrome.

Clinical and genetic characterization of nephropathy in patients with nail-patella syndrome.

Nail-patella syndrome (NPS) is a multi-system disorder characterized by hypoplastic nails, hypoplastic patella, skeletal deformities, and iliac horns, which is caused by heterozygous variants of LMX1B. Nephropathy ranging from mild urinary abnormality to end-stage renal disease occurs in some individuals with NPS. Because of the low prevalence of NPS and the lack of longitudinal studies of its kidney involvement, the clinical, pathological, and genetic features characterizing severe nephropathy remain unclear. We conducted a Japanese survey of NPS with nephropathy, and analyzed their clinical course, pathological features, and factors associated with severe renal phenotype. LMX1B gene analysis and luciferase reporter assay were also performed. Among 13 NPS nephropathy cases with genetic validation, 5 patients who had moderate-to-massive proteinuria progressed to advanced chronic kidney disease or end-stage renal disease. Pathological findings in the early phase did not necessarily correlate with renal prognosis. Variants associated with deteriorated renal function including a novel variants were confined to the N-terminal region of the LIM domain and a short sequence in the LMX1B homeodomain, which were distinct from reported variants found in isolated nephropathy without extrarenal manifestation (LMX1B-associated nephropathy). Luciferase reporter analysis demonstrated that variants in patients with severe renal phenotype caused haploinsufficiency, but no dominant-negative effects on promoter activation. A distinct proportion of NPS nephropathy patients progressed to end-stage renal disease in adolescence or young adulthood. Patients with moderate or severe proteinuria, especially those with variants in specific regions of LMX1B, should be monitored for potential deterioration of renal function.

Internal Carotid Artery Aplasia in a Patient With Nail-Patella Syndrome.

Nail-patella syndrome (NPS) is a rare disorder characterized by abnormal development of ectodermal and mesodermal tissues. Classically, NPS presents as a triad of nail dysplasia, dysplastic patellae, and bony exostoses of the ilia known as "iliac horns." Apart from dermatological and skeletal abnormalities, patients may also have involvement of ophthalmologic and renal systems. The underlying molecular etiology in NPS is the mutation of LMX1B homeobox gene which results in loss of function of its protein also called LMX1B, a DNA-binding protein belonging to the larger LIM-homeodomain transcription factor family. Normal LMX1B gene and protein function are essential for dorsalization of the vertebrate limb bud, development of anterior eye structures, skull formation, and differentiation and migration of neurons in the central nervous system. We report a case of confirmed NPS presenting with congenital aplasia of the internal carotid artery and believe this is the first report of cerebrovascular developmental abnormality associated with NPS.

Electron Microscopic and Immunohistochemical Findings of the Epidermal Basement Membrane in Two Families with Nail-patella Syndrome.

Nail-patella syndrome is an autosomal dominant disorder characterized by nail dysplasia and skeletal anomaly. Some patients have been shown to have ultrastructural abnormalities of the glomerular basement membrane that result in nephrosis. However, little has been reported on the epidermal basement membrane in this condition. This paper reports 2 families with nail-patella syndrome. Direct sequencing analysis of LMX1B revealed that family 1 and family 2 were heterozygous for the mutations c.140-1G>C and c.326+1G>C, respectively. To evaluate the epidermal basement membrane zone, ultrastructural and immunohistochemical analyses were performed using skin specimens obtained from the dorsal thumb. Electron microscopy showed intact hemidesmosomes, lamina lucida, lamina densa, and anchoring fibrils. Immunofluorescence studies with antibodies against components of the epidermal basement membrane zone revealed a normal expression pattern among the components, including type IV collagen. These data suggest that nail dysplasia in patients with nail-patella syndrome is not caused by structural abnormalities of the epidermal basement membrane.

A novel small deletion of LMX1B in a large Chinese family with nail-patella syndrome.

BACKGROUND: Nail-patella syndrome (NPS) is an autosomal dominant developmental disorder most commonly characterized by dyplasia of nail or patella, the radial head or the humeral head hypoplasia, and, frequently ocular abnormalities and renal disease. It is caused by heterozygous loss-of-function mutations in the LMX1B gene, which encodes LIM homeodomain transcription factor and is essential for regulating the dorsal limb fate. METHODS: A five generation pedigree was recruited. Genomic DNA was extracted from the peripheral blood samples. Mutation detection was performed by Sanger sequencing the LMX1B gene. In silico functional annotation of the variant was performed using the in silico predictors SIFT, PolyPhen-2 and Mutation Taster. RESULTS: A novel heterozygous small deletion within exon 4 of LMX1B, c.712_714delTTC, was identified in a rare five-generation NPS pedigree. The mutation resulted in a deletion of the conserved amino acid phenylalanine at codon 238 (p.Phe238del), which located in the homeodomain of LMX1B may abolish DNA binding with the molecule. Conformational prediction showed that the variation could transform the helical structure comprising p.Phe234, p.Lys235, p.Ala236, and p.Ser237. CONCLUSION: We identified a novel NPS-causing LMX1B mutation and expanded the spectrum of mutations in the LMX1B gene. The c.712_714delTTC mutation may affect the quaternary structure of LMX1B, which is essential for the specification of dorsal limb fate at both zeugopodal and autopodal levels, leading to typical NPS.

Schizophrenia and Nail Patella Syndrome: The Dopamine Connection.

BACKGROUND: Nail-patella syndrome (NPS) is characterized by changes in the nails, knees, and elbows, as well as the presence of iliac horns detected by X-ray of the pelvis. A higher occurrence of psychiatric disorders has also been suggested in NPS. Heterozygous mutations in the gene encoding the LIM-homeodomain transcription factor (LMX1B) are identified in most patients with typical clinical findings of NPS. OBJECTIVES: To report on the association between NPS and schizophrenia. METHODS: Genomic DNA were isolated from a patient's venous blood and collected on ethylenediaminetetraacetic 5% with the Gentra Puregene Blood Kit. All exons and flanking regions of the LMX1B gene (LMX1B: NM_001174146.1) were amplified by standard polymerase chain reaction and analyzed by direct DNA sequencing with BigDye Terminators on an ABI 3100 sequencer. Sequence chromatograms were analyzed using SeqScape software version 1.1. Mutation analysis and characterization of variants was performed with the Alamut Software Version 2.1. RESULTS: We report a patient presenting to the psychiatry department with schizophrenia. Clinical examination revealed characteristic findings consistent with NPS. Since NPS was suspected, based on clinical findings, sequencing of all coding exons of LMX1B gene was completed. Results revealed a novel heterozygous mutation in the proband: c.546_547insACCG(het); p.Glu183Thrfs*11. CONCLUSIONS: Based on LMX1B expression in brain regions that are implicated in neuropsychiatric illness, and especially in the development of dopaminergic neurons, we hypothesize that schizophrenia may be part of the clinical spectrum of NPS.

Could the interaction between LMX1B and PAX2 influence the severity of renal symptoms?

Nail Patella syndrome (NPS) is a rare autosomal dominant disease characterized by varying degrees of patella, nail, and elbows dysplasia and also ocular and renal congenital abnormalities. The renal involvement, ranging from hematuria and proteinuria to end-stage renal disease, is present in 22-60% of NPS cases. Heterozygous variants in LMX1B are known to be responsible of NPS and it has been hypothesized that the variable expressivity is due to the interaction of LMX1B with other developmental genes. We reported a case of co-presence of LMX1B and PAX2 variants in a child with extrarenal manifestation of NPS and end-stage renal disease but congenital bilateral renal hypodysplasia and vesicoureteral reflux. The LMX1B variant was de novo, whereas the PAX2 variant was inherited from the mother that had bilateral renal hypoplasia although in presence of only a mild chronic kidney disease. The molecular interaction between LMX1B and PAX2 has been already reported in vitro and this finding suggest that the worst renal NPS phenotype of our patient could be due to the defective expression of these two genes during nephrogenesis. In conclusion, our finding suggests that PAX2 may act as modifier gene in Nail Patella phenotype.