De novo enhancer deletion of LMX1B produces a mild nail-patella clinical phenotype

Critical genes involved in embryonic development are often transcription factors, regulating many downstream genes. LMX1B is a homeobox gene that is involved in formation of the limbs, eyes and kidneys, heterozygous loss-of-function sequence variants and deletions cause Nail-Patella syndrome. Most of the reported variants are localised within the gene's coding sequence, however, approximately 5%-10% of affected individuals do not have a pathogenic variant identified within this region. In this study, we present a family with four affected individuals across two generations with a deletion spanning a conserved upstream LMX1B-binding sequence. This deletion is de novo in the mother of three affected children. Furthermore, in this family, the manifestations appear limited to the nails and limbs, and therefore may reflect an attenuated phenotype of the classic Nail-Patella phenotype that includes ophthalmological and renal manifestations.

Dilated Cardiomyopathy and Nail-Patella Syndrome: A Case Report

Nail-patella syndrome (NPS) is a rare genetic disorder with multiple skeletal deformities and a variety of extra-skeletal involvements. We present a 17-year-old male with a clinical tetrad of skeletal abnormalities, multiple bony deformities, advanced renal failure, hypothyroidism, and dilated cardiomyopathy. A clinical diagnosis of NPS was made, supported by radiographic findings, and corroborated by compatible renal biopsy results. There are very few published reports describing the association of dilated cardiomyopathy with this syndrome. A high index of suspicion is needed to make this diagnosis, given myriads of multi-systemic manifestations.

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.

Retrospective Diagnosis of Nail-patella Syndrome

A 37 years old female presented with asymptomatic nephrotic range proteinuria due to focal segmental glomerulosclerosis (FSGS). She was treated with steroids and mycophenolate mofetil to which there was no response and progressed to advanced chronic kidney disease. When her brother who was being evaluated as a potential donor, for renal transplant, was found to have proteinuria and a genetic study for the steroid-resistant nephrotic syndrome was done. This revealed mutation in the LMX1B gene. It is then that a diagnosis of nail-patella syndrome (NPS) was made. She underwent a successful renal transplant with her father as a donor and is doing well.

A Novel Mutation in LMX1B (p.Pro219Ala) Causes Focal Segmental Glomerulosclerosis with Alport Syndrome-like Phenotype

A 69-year-old woman presented with mild renal dysfunction, proteinuria, and sensorineural hearing loss. A renal biopsy showed focal segmental glomerulosclerosis with thinning of the glomerular basement membrane. There was a positive family history of end-stage kidney disease and hearing loss. Although Alport syndrome was suspected from these features, a genetic test using next-generation sequencer identified a novel missense mutation in LMX1B, c.655C>G: p. (Pro219Ala). In silico analyses predicted the pathogenicity of the mutation. Thus, the present case was diagnosed as LMX1B-associated nephropathy presenting with Alport syndrome-like phenotype, expanding the disease spectrum of LMX1B nephropathy.

Case Report: Corneal Leucoma as a Novel Clinical Presentation of Nail-Patella Syndrome in a 5-Year-Old Girl

Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder characterized by the classic tetrad of absent or hypoplastic finger and toe nails, absent or hypoplastic patella, skeletal deformities involving the elbow joints, and iliac horns. This disease is caused by heterozygous pathogenic variations in the LMX1B gene, which encodes the LIM homeodomain transcription factor protein (LMX1B). We report a case of corneal leucoma and dysplasia prior to overt steroid-resistant nephrotic syndrome (SRNS) in a patient with NPS. At presentation, the parents of a 5-year-old female patient reported their daughter had corneal leucoma, psychomotor delay and speech defect. We also noted the presence of bilateral edema of the lower extremities, hypertension, nail dystrophy, and the bilateral absence of patella. She developed steroid-resistant nephrotic syndrome. Lowe oculocerebrorenal syndrome and NPS were the conditions considered in differential diagnosis. Trio-based whole genome sequencing indicated a heterozygous de novo likely pathogenic variation in the LMX1B gene (c.805A>C [p.Asn269His]). Patients with NPS often develop nail, ocular, or orthopedic symptoms prior to nephrotic syndrome. Corneal leucoma may be a novel clinical presentation of NPS.

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.

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.

Nail-Patella syndrome with early onset end-stage renal disease in a child with a novel heterozygous missense mutation in the LMX1B homeodomain: A case report

Nail-Patella syndrome (NPS) is an inherited disease characterized by nail and skeletal anomalies, nephropathy and glaucoma. The diagnosis of NPS is based on clinical findings, including hypoplastic or absent patella, dystrophic nails, dysplasia of the elbows and iliac horns. However, the main determinant of NPS prognosis is nephropathy, which may range from asymptomatic proteinuria to end-stage renal disease. NPS is caused by heterozygous loss-of-function mutations in the LMX1B gene, which encodes the LIM homeodomain transcription factor LMX1B. LMX1B serves an essential role in the physiological development of dorsal-ventral limb structures, morphogenesis and function of podocytes, as well as in development of the anterior segments of the eyes, and in certain types of neurons. The present study aimed to identify the disease-causing mutation in a 2-year old girl with nephrotic syndrome that evolved rapidly to end-stage renal disease. The patient showed classical symptoms of NPS including dystrophic nails and an absence of the patellae. DNA sequence analysis identified a novel missense variant in exon 4 of LMX1B (c.709T>C, p.S237P); this substitution affected a conserved serine residue in the homeodomain of LMX1B and was predicted to be pathogenic. In silico modeling of the homeodomain revealed that the p.S237P mutation converted the A236-S237-F238 segment of α-helix 1 into a strand. It was hypothesized that this mutation affected binding of the transcription factor to its target DNA, thus abrogating transcription activation, which would explain the phenotype that manifested in the patient.

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.

Novel missense mutation affecting the LIM-A domain of LMX1B in a family with Nail-Patella syndrome

Nail-patella syndrome (NPS) is a rare autosomal dominant disease characterized by developmental defects of dorsal limb structures, the kidney, and the eye, that manifest as dysplastic nails, hypoplastic or absent patella, elbow dysplasia, iliac horns, glomerulopathy, and adult-onset glaucoma, respectively. This disorder is inherited in an autosomal dominant mode and is caused by heterozygous loss-of-function mutations in the LMX1B gene, which encodes the LIM homeodomain transcription factor LMX1B. In this study, we report the clinical findings of a Spanish family, from the Canary Islands, with three affected members who displayed varying phenotypes. DNA sequence analysis identified a novel heterozygous missense mutation in LMX1B, c.305A>G, p.(Y102C), that segregated with the disease. The tyrosine residue affected by the mutation is highly conserved in evolution, and is located in the LIM-A domain, next to one of the cysteine residues involved in zinc binding, suggesting that p.(Y102C) affects LMX1B function by disturbing its interactions with other proteins. Our results expand the mutation spectrum of LMX1B and provide insight into the molecular mechanisms of NPS pathology.

LMX1B-Associated Nephropathy With Type III Collagen Deposition in the Glomerular and Tubular Basement Membranes

Variants in the LMX1B gene cause nail-patella syndrome, a rare autosomal dominant disorder characterized by dysplasia of nails, patella and elbow abnormalities, iliac "horns," and glaucoma. We describe an adult man with nephrotic syndrome and no systemic manifestations of nail-patella syndrome at the time of his initial kidney biopsy. His kidney biopsy was initially interpreted as a form of segmental sclerosis with unusual fibrillar deposits. At the time of consideration for kidney transplantation, a family history was notable for end-stage renal disease in 3 generations. Subsequent reanalysis of the initial biopsy showed infiltration of the lamina densa by type III collagen fibrils, and molecular studies identified a pathogenic variant in one allele of LMX1B (a guanine to adenine substitution at nucleoide 737 of the coding sequence [c.737G>A], predicted to result in an arginine to glutamine substitution at amino acid 246 [p.Arg246Gln]). This variant has been described previously in multiple unrelated families who presented with autosomal dominant nephropathy without nail and patellar abnormalities.

Clinical and histological findings of autosomal dominant renal-limited disease with LMX1B mutation

AIM

Mutations of LMX1B cause nail-patella syndrome, a rare autosomal dominant disorder. Recently, LMX1B R246Q heterozygous mutations were recognised in nephropathy without extrarenal manifestation. The aim of this study was to clarify characteristics of nephropathy caused by R246Q mutation.

METHODS

Whole exome sequencing was performed on a large family with nonsyndromic autosomal dominant nephropathy without extrarenal manifestation. Clinical and histological findings of patients with LMX1B mutation were investigated.

RESULTS

LMX1B R246Q heterozygous mutation was identified in five patients over three generations. Proteinuria or haematoproteinuria was recognized by urinary screening from all patients in childhood. Proteinuria gradually increased to nephrotic levels and renal function decreased in adolescence. Two patients progressed to end-stage renal disease in adulthood. Renal histology demonstrated minimal change in childhood and focal segmental glomerulosclerosis in adulthood. Using electron microscopy, focal collagen deposition could be detected in glomeruli even when a "moth-eaten appearance" was not apparent in the glomerular basement membrane. In addition, podocin expression in glomerular podocytes was significantly decreased, even in the early stages of disease progression.

CONCLUSION

Comprehensive genetic analyses and collagen or tannic acid staining may be useful for diagnosis of LMX1B-associated nephropathy. While renal prognosis of R246Q may be worse than that of typical NPS nephropathy, signs of podocytopathy can be detected during the infantile period; thus, childhood urinary screening may facilitate early detection.

Arthropathy and proteinuria: nail-patella syndrome revisited

Nail-patella syndrome (NPS) is a pleiotropic autosomal-dominant disorder due to mutations in the gene LMX1B. It has traditionally been characterized by a tetrad of dermatologic and musculoskeletal abnormalities. However, one of the most serious manifestations of NPS is kidney disease, which may be present in up to 40% of affected individuals. Although diagnosis can be made at birth, it is often missed, presumably due to the rarity of the condition.

A 35-year-old female presented to our clinic with history of small joint pain of 6 months duration. In addition she complained of pedal edema off and on for the last 12 years. Prior to her current presentation she had been managed by a local doctor symptomatically. On evaluation, a nephrotic syndrome was obvious, but no secondary cause could be found. However, her physical examination was characteristic of NPS and keeping in view the autosomal dominant nature of the disorder all her three siblings were screened who too showed classical features of NPS. This rare syndrome as a cause of nephrotic range proteinuria is discussed in this report. The report underlines the importance of a good physical examination in a given clinical setting.

A case of nail-patella syndrome associated with thyrotoxicosis

Nail-patella syndrome, also known as hereditary onycho-osteodystrophy, is a rare autosomal dominant disorder with pleiotropic phenotypic expression.The present report is of a nail-patella syndrome patient, a 26-year-old female, admitted to our NeuroMuscular Rehabilitation Clinic Division for neurological symptoms, secondary to a severe spondylolysthesis with bilateral L5 pedicle fracture. During hospitalization, she was also diagnosed with mild thyrotoxicosis, but interestingly enough, the bone mineral density, assessed at multiple sites, was quasi-normal.