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.

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.

Nail-patella-like renal disease masquerading as Fabry disease on kidney biopsy: a case report.

BACKGROUND: Genetic changes in the LIM homeobox transcription factor 1 beta (LMX1B) have been associated with focal segmental glomerulosclerosis (FSGS) without the extra-renal or ultrastructural manifestations of Nail-patella syndrome (NPS) known as Nail-patella-like renal disease (NPLRD). Fabry disease (FD) is an X-linked lysosomal disease caused by the deficiency of alpha-galactosidase A. The classic form of the disease is characterized by acroparesthesia, angiokeratomas, cornea verticillata, hypertrophic cardiomyopathy, strokes, and chronic kidney disease. Podocyte myelin bodies on ultrastructural examination of kidney tissue are very characteristic of FD; however some medications and other conditions may mimic this finding. CASE PRESENTATION: Here, we report on a female patient with chronic kidney disease (CKD), positive family history for kidney disease and kidney biopsy showing a FSGS lesion and presence of focal myelin figures within podocytes concerning for FD. However, genetic testing for FD was negative. After comprehensive clinical, biochemical, and genetic evaluation, including whole exome and RNA sequencing, she was ultimately diagnosed with NPLRD. CONCLUSIONS: This case illustrates the difficulties of diagnosing atypical forms of rare Mendelian kidney diseases and the role of a multidisciplinary team in an individualized medicine clinic setting in combination with state-of-the-art sequencing technologies to reach a definitive diagnosis.

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.

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.

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.

Nail-patella syndrome.

The pathognomonic symptoms of patients with nail-patella syndrome are their small or absent patellae and dysplastic or absent finger- and toenails. Many of the patients suffer from renal symptoms which also affect their prognosis. In 1998, mutations in the gene encoding the transcription factor LMX1B were identified as underlying this autosomal-dominant disease. The LMX1B gene is expressed in a variety of tissues, and the symptoms are reflected nicely by its expression pattern. LMX1B is essential for dorso-ventral pattern formation in the limbs, for differentiation of the anterior portions of the eyes, for development of certain neuron populations in the central nervous system, and for the differentiation and maintenance of podocytes. Accordingly, kidney biopsies of patients with nail-patella syndrome show an altered podocyte structure and defects in the glomerular basement membrane. Recent evidence suggests that LMX1B regulates genes which encode proteins associated with the actin cytoskeleton.

Steroid-resistant nephrotic syndrome as the initial presentation of nail-patella syndrome: a case of a de novo LMX1B mutation.

BACKGROUND: Nail-patella syndrome (NPS) is an autosomal dominant disorder caused by mutations in the LMX1B gene and is characterized by nail dysplasia, skeletal abnormalities, and nephropathy. We herein report a case of steroid-resistant nephrotic syndrome (SRNS) prior to overt orthopedic symptoms in a patient with NPS. CASE PRESENTATION: A 24-year-old woman presented to our hospital with knee pain. She had poorly developed nails, hypoplastic patellas, dislocation of the elbows, and iliac horns in the pelvis. At the age of 7, she developed nephrotic syndrome and was diagnosed with primary focal segmental glomerulosclerosis by renal biopsy. She received long-term corticosteroid therapy with no obvious response. Her clinical course and orthopedic manifestations indicated NPS, and a genetic analysis showed a de novo mutation in the LMX1B gene (c.819 + 1G > A). Nephropathy in this case was considered to be associated with NPS. Therefore, we discontinued corticosteroids without the exacerbation of nephrotic syndrome. CONCLUSIONS: Patients with NPS may develop nephrotic syndrome prior to overt orthopedic symptoms and only show non-specific findings in renal biopsy at an early stage of NPS nephropathy. Hereditary nephrotic syndrome, often presenting as childhood-onset SRNS, may also be difficult to diagnose in patients with the following conditions: renal symptoms prior to overt extrarenal symptoms, de novo mutations, and non-specific findings in renal biopsy. Therefore, in the management of SRNS in children, we need to reconsider the possibility of hereditary diseases such as NPS even without a family history.

Nail-patella syndrome: report of 11 pediatric cases.

BACKGROUND: Nail-patella syndrome (NPS) is an inherited disease produced by mutations in the LMX1B gene. It is characterized by fingernail dysplasia, hypoplastic or absent patella, dysplasia of the elbows and iliac horns on X-ray. It is useful to know this syndrome since some patients develop nephropathy and eye abnormalities. There are very few accurate descriptions related to this syndrome in the literature. OBJECTIVE: Describe the features of 11 patients with NPS in a paediatric hospital. METHODS: We retrospectively reviewed our clinical database of 11 patients with proven diagnosis of NPS from 1977 to 2014. Clinical and radiological features were assessed. RESULTS: Eleven children (seven male/four female) were included in the study. Mean age at the time of diagnosis was 6.54 years (range 0-11 years). Five patients had a family history of NPS. All patients had nail abnormalities (100%), the most frequent finding being hyponychia. Triangular lunulae were observed in four patients. The knee was the most commonly affected joint, aplasia or hypoplasia of the patella being the most usual findings. Only one patient presented renal involvement. The genetic study revealed three different LMX1B mutations. CONCLUSION: Nail-patella syndrome is a rare disorder. The aim of the present study is to highlight the importance of nail examination in children with skeletal dysplasias, in order to diagnose the NPS.

Nail-Patella Syndrome: clinical and molecular data in 55 families raising the hypothesis of a genetic heterogeneity.

Nail-Patella Syndrome (NPS) is a rare autosomal dominant condition comprising nail and skeletal anomalies. Skeletal features include dysplastic patellae and iliac horns, as well as scapula and elbow dysplasia. Nephropathy and glaucoma or intra-ocular hypertension can sometimes be present. NPS is due to variants affecting function in LMX1B, which encodes a LIM-homeodomain protein critical for limb, kidney and eye development. We describe the phenotype and the molecular data of 55 index patients and their 39 relatives presenting with typical NPS. We identified 38 different LMX1B anomalies, 19 of which were not reported before. In our series, 9% of families are not carriers of a LMX1B genomic alteration after extensive study of the coding and non-coding regions of the gene. One of the families showed no linkage to the LMX1B locus, raising the hypothesis of a genetic heterogeneity.

Nail-Patella Syndrome: A Report of a Saudi Arab Family With an Autosomal Recessive Inheritance.

BACKGROUND: Nail-patella syndrome (NPS) is an autosomal dominant disorder with a variable interfamilial and intrafamilial clinical expressivity and penetrance. It is caused by loss-of-function heterozygous mutation in the LIM-homeodomain transcription factor (LMX1B) located on chromosome 9q. The pleiotropic LMB1X gene, a member of the homeogene family, is involved in the development of glomerular basement membrane, dorsoventral limb structures, along with the nails and the anterior segment of the eye. OBJECTIVE: Here, we report a Saudi Arab consanguineous family with 2 affected sisters presented with the typical nail changes of NPS. METHODS: DNA samples were collected from the sisters and their parents after consent. RESULTS: Both sisters were found to be homozygous for a previously described disease-causing mutation (c.268C>T) at the (LMX1B) gene. Both of the phenotypically normal parents were confirmed to be heterozygous for the same mutation. CONCLUSION: This finding supports the autosomal recessive mode of inheritance in this family.

[Alterations in nails and teeth as a clue for genodermatoses]. / Anomalien der Nägel und Zähne als Schlüssel für die Diagnose von Genodermatosen.

BACKGROUND: There are about 10,000 monogenic diseases and around 30% demonstrate alterations in the skin and its appendages. As there are so many genetic different skin diseases, clear diagnosis is often very difficult. AIM: The goal of this review is to give the clinicians some key features on nails and teeth which might help to identify rare genodermatoses. DISCUSSION: In the daily work genodermatoses manifest more commonly as incomplete or oligosymptomatic syndromes than as complete symptom complexes. To diagnose a rare disorder in such situations, a knowledge of key features which are characteristic for a genodermatoses is essential, so that a diagnosis can be advanced and the underlying gene defect identified. Changes in nails and teeth sometimes may be useful as diagnostic key features. Both structures originate from ectoderm and therefore they often appear in combination in diseases with major ectodermal malformations. Enamel defects resembling the lines of Blaschko are highly suggestive for focal dermal hypoplasia, even if other important signs and symptoms are missing. Enamel defects combined with gingival fibromas are highly suggestive for tuberous sclerosis. On the other side, triangular lunulae with malformation and dystrophy of the nail plate suggests nail-patella syndrome.

LMX1B mutation with residual transcriptional activity as a cause of isolated glomerulopathy.

BACKGROUND: Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder caused by LMX1B mutation. In patients with the renal lesions typical of NPS without skeletal or nail findings, it is described as nail-patella-like renal disease (NPLRD). However, the pathogenesis of NPLRD is largely unknown. METHODS: A 6-year-old girl with microscopic haematuria and mild proteinuria was diagnosed with NPLRD because of an aberrantly thickened glomerular basement membrane (GBM) and deposition of Type III collagen in the GBM observed by electron microscopy. Immunohistological analyses of podocyte protein expression were performed on biopsy tissues. Sequence analysis of LMX1B was performed, and the functional consequences of the detected mutation were analysed by luciferase reporter assay. RESULTS: When analysing molecules that are important for podocyte development, maintenance and maturation, CD2AP expression was found to be altered in the podocytes. A novel LMX1B missense mutation (R246Q) was identified. Functional analyses revealed partial but significant impairment of R246Q transcriptional activity. However, no dominant-negative effect of R246Q was detected, which suggests that NPLRD is caused by LMX1B haploinsufficiency. CONCLUSIONS: This is the first report on LMX1B mutation identified in a patient with NPLRD. Residual transcriptional activity would account for normality of the nails and patella in this case. Genetic and pathological analyses of additional cases would clarify the role of LMX1B in glomerulopathy without systemic symptoms, which, together with nephropathy in NPS, can be designated as 'LMX1B nephropathy'.

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.

Nail-patella syndrome with an emphasis on the risk of renal and ocular findings.

We describe a 6-year-old girl presenting with nail dysplasia affecting all nails and hands for 2 years. Changes were seen on the ulnar side of the nails. She was assessed for limitation of elbow movements at 3 weeks of age and underwent physiotherapy for thickened biceps tendon. She subsequently developed laxity of knees and ankles, and x-ray revealed absent patellae at 32 weeks. She had behavioral abnormalities and sleep disturbances. X-ray of the pelvis revealed iliac horns, and urinalysis showed 3+ proteinuria. She had mixed hyperlipidemia. Her chromosomal analysis was normal but showed a mutation in the LMX1B gene. She was diagnosed to have Nail-patella syndrome or Hereditary osteo-onychodysplasia (HOOD Syndrome). Her renal imaging was normal, as were her ocular pressures. She is under regular surveillance by a multi-disciplinary team of genetic counselors, orthopedists, rheumatologists and ophthalmologists. She is currently prescribed enalapril, melatonin and simvastatin.

Banded collagen in the kidney with special reference to collagenofibrotic glomerulopathy.

BACKGROUND: The normal glomerular basement membrane, composed of type IV collagen, plays an important function in the process of filtration. Rarely, type III, type I, or type V collagen is seen in the glomerulus, resulting in three different types of non-immune mediated glomerulopathies recognized thus far. These are characterized by deposition of banded collagen fibers in the glomerulus. METHODS: The authors reviewed 4934 kidney biopsies submitted over the past 5 years. Five of these revealed the presence of banded collagen in the glomeruli. CONCLUSION: Combined clinical and ultrastructural examination has led to a definitive diagnosis. These diseases exhibit indolent progression and as yet do not have specific treatment.