Nail-patella syndrome

The genetics of spontaneous coronary artery dissection: a scoping review

BACKGROUND

Spontaneous coronary artery dissection (SCAD) is a multifactorial process that involves predisposing factors and precipitating stressors. Genetic abnormality has been implicated to play a mechanistic role in the development of SCAD. This systematic review aims to summarize the current evidence concerning the link between SCAD and genetic abnormalities.

METHODS

We reviewed original studies published until May 2023 that reported SCAD patients with a genetic mutation by searching PubMed, Embase Ovid, and Google Scholar. Registries, cohort studies, and case reports were included if a definitive SCAD diagnosis was reported, and the genetic analysis was performed. Exclusion criteria included editorials, reviews, letters or commentaries, animal studies, meeting papers, and studies from which we were unable to extract data. Data were extracted from published reports.

RESULTS

A total of 595 studies were screened and 55 studies were identified. Among 116 SCAD patients with genetic abnormalities, 20% had mutations in the COL gene, 13.70% TLN1 gene, and 8.42% TSR1 gene. Mutations affecting the genes encoding COL and TLN1 were most frequently reported (20 and 13.7%, respectively). Interestingly, 15 genes of this collection were also reported in patients with thoracic aortic diseases as well. The genetic commonality between fibromuscular dysplasia (FMD) and SCAD was also included.

CONCLUSION

In this review, the inherited conditions and reported genes of undetermined significance from case reports associated with SCAD are collected. A brief description of the encoded protein and the clinical features associated with pathologic genes is provided. Current data suggested that the diagnostic yield of genetic studies for patients with SCAD would be low and routine genetic screening of such patients with no clinical features indicative of associated disorders remains debatable. This review can be used as a guide for clinicians to recognize inherited syndromic and nonsyndromic disorders associated with SCAD.

Case report: A novel R246L mutation in the LMX1B homeodomain causes isolated nephropathy in a large Chinese family

BACKGROUND

Genetic factors contribute to chronic kidney disease (CKD) and end-stage renal disease (ESRD). Advances in genetic testing have enabled the identification of hereditary kidney diseases, including those caused by LMX1B mutations. LMX1B mutations can lead to nail-patella syndrome (NPS) or nail-patella-like renal disease (NPLRD) with only renal manifestations.

CASE PRESENTATION

The proband was a 13-year-old female who was diagnosed with nephrotic syndrome at the age of 6. Then she began intermittent hormone and drug therapy. When she was 13 years old, she was admitted to our hospital due to sudden chest tightness, which progressed to end-stage kidney disease (ESRD), requiring kidney replacement therapy. Whole-Exome Sequencing (WES) results suggest the presence of LMX1B gene mutation, c.737G > T, p.Arg246Leu. Tracing her family history, we found that her father, grandmother, uncle and 2 cousins all had hematuria, or proteinuria. In addition to the grandmother, a total of 9 members of the family performed WES. The members with kidney involved all carry the mutated gene. Healthy members did not have the mutated gene. It is characterized by co-segregation of genotype and phenotype. We followed the family for 9 year, the father developed ESRD at the age of 50 and started hemodialysis treatment. The rest patients had normal renal function. No extra-renal manifestations associated with NPS were found in any member of the family.

CONCLUSIONS

This study has successfully identified missense mutation, c.737G > T (p.Arg246Leu) in the homeodomain, which appears to be responsible for isolated nephropathy in the studied family. The arginine to leucine change at codon 246 likely disrupts the DNA-binding homeodomain of LMX1B. Previous research has documented 2 types of mutations at codon R246, namely R246Q and R246P, which are known to cause NPLRD. The newly discovered mutation, R246L, is likely to be another novel mutation associated with NPLRD, thus expanding the range of mutations at the crucial renal-critical codon 246 that contribute to the development of NPLRD. Furthermore, our findings suggest that any missense mutation occurring at the 246th amino acid position within the homeodomain of the LMX1B gene has the potential to lead to NPLRD.

A deletion variant in LMX1B causing nail-patella syndrome in Japanese twins

Nail-patella syndrome (NPS) is a hereditary disease caused by pathogenic variants in LMX1B and characterized by nail, limb, and renal symptoms. This study revealed a likely pathogenic LMX1B variant, NM_002316.4: c.723_726delinsC (p.Ser242del), in Japanese twins with clubfoot. The patients' mother, who shared this variant, developed proteinuria after delivery. p.Ser242del is located in the homeodomain of the protein, in which variants that cause renal disease tend to cluster. Our findings highlight p.Ser242del as a likely pathogenic variant, expanding our knowledge of NPS.

Podocyte-specific Transcription Factors: Could MafB Become a Therapeutic Target for Kidney Disease?

The increasing number of patients with chronic kidney disease (CKD) is being recognized as an emerging global health problem. Recently, it has become clear that injury and loss of glomerular visceral epithelial cells, known as podocytes, is a common early event in many forms of CKD. Podocytes are highly specialized epithelial cells that cover the outer layer of the glomerular basement membrane. They serve as the final barrier to urinary protein loss through the formation and maintenance of specialized foot-processes and an interposed slit-diaphragm. We previously reported that the transcription factor MafB regulates the podocyte slit diaphragm protein production and transcription factor Tcf21. We showed that the forced expression of MafB was able to prevent CKD. In this review, we discuss recent advances and offer an updated overview of the functions of podocyte-specific transcription factors in kidney biology, aiming to present new perspectives on the progression of CKD and respective therapeutic strategies.

Imaging More than Skin-Deep: Radiologic and Dermatologic Presentations of Systemic Disorders

Background: Cutaneous manifestations of systemic diseases are diverse and sometimes precede more serious diseases and symptomatology. Similarly, radiologic imaging plays a key role in early diagnosis and determination of the extent of systemic involvement. Simultaneous awareness of skin and imaging manifestations can help the radiologist to narrow down differential diagnosis even if imaging findings are nonspecific. Aims: To improve diagnostic accuracy and patient care, it is important that clinicians and radiologists be familiar with both cutaneous and radiologic features of various systemic disorders. This article reviews cutaneous manifestations and imaging findings of commonly encountered systemic diseases. Conclusions: Familiarity with the most disease-specific skin lesions help the radiologist pinpoint a specific diagnosis and consequently, in preventing unnecessary invasive workups and contributing to improved patient care.

Loss of CLDN5 in podocytes deregulates WIF1 to activate WNT signaling and contributes to kidney disease

Although mature podocytes lack tight junctions, tight junction integral membrane protein claudin-5 (CLDN5) is predominantly expressed on plasma membranes of podocytes under normal conditions. Using podocyte-specific Cldn5 knockout mice, we identify CLDN5 as a crucial regulator of podocyte function and reveal that Cldn5 deletion exacerbates podocyte injury and proteinuria in a diabetic nephropathy mouse model. Mechanistically, CLDN5 deletion reduces ZO1 expression and induces nuclear translocation of ZONAB, followed by transcriptional downregulation of WNT inhibitory factor-1 (WIF1) expression, which leads to activation of WNT signaling pathway. Podocyte-derived WIF1 also plays paracrine roles in tubular epithelial cells, as evidenced by the finding that animals with podocyte-specific deletion of Cldn5 or Wif1 have worse kidney fibrosis after unilateral ureteral obstruction than littermate controls. Systemic delivery of WIF1 suppresses the progression of diabetic nephropathy and ureteral obstruction-induced renal fibrosis. These findings establish a function for podocyte CLDN5 in restricting WNT signaling in kidney.

Claudin-5 is a tight junction integral membrane protein, but it is also expressed in mature podocytes which lack tight junctions. Here the authors report that podocyte claudin-5 regulates WNT signaling activity by modulating WIF1 expression, and its downregulation contributes to kidney disease progression in mice.

Robotic-Assisted Lateral Unicompartmental Knee Arthroplasty in a Patient With Nail-Patella Syndrome

A 59-year-old woman with nail patella syndrome (NPS) presented with progressive and severe right knee pain for the past 3 years. Imaging demonstrated laterally dislocated patella, with asymmetric femoral trochlea, and advanced lateral compartment arthritis. The patient underwent robotic-assisted lateral unicompartmental knee arthroplasty (RAUKA). The patient saw marked improvements in patient-reported outcome measurements from her initial visit to the last follow-up visit. While treatment of knee osteoarthritis in patients with NPS can be difficult, especially with attempts of patellar realignment, we present a case of a patient who underwent RAUKA, with sustained improvements in patient outcomes and range of motion, at the 2-year follow-up visit. This study is the first of its kind to demonstrate the use of a novel technology in a rare condition.

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.

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.

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.

Plateau iris syndrome and angle-closure glaucoma in a patient with nail-patella syndrome

Purpose

To describe a case of plateau iris syndrome (PIS) and angle-closure glaucoma (ACG) in a patient with nail-patella syndrome (NPS).

Observation

A 33 year-old woman of Slovakian ancestry from Norway with a history of NPS presented with angle-closure secondary to plateau iris. At the time of her NPS diagnosis, she had no ocular pathology. Genetic testing revealed a rare de novo mutation in LMX1B [c.668G>C (p.Arg223Pro)]. Two years later, she experienced acute bilateral ocular pain and blurred vision in the setting of one year of reported visual loss. Subsequent ophthalmic examinations revealed closed angles and plateau iris OU with ACG OD and angle-closure OS. Perimetry showed superonasal visual field defects OD and no defects OS. Ocular coherence tomography (OCT) revealed thinning of the inferior pole of the optic nerve OD. Medical management proved ineffective. A laser peripheral iridotomy (LPI) OD was performed, without resolution of the angle-closure, and a diagnosis of plateau iris syndrome (PIS) was made. She was then treated with an argon laser peripheral iridoplasty (ALPI) and clear lens extraction with a posterior chamber intraocular lens (PCIOL) and goniosynechialysis OD, but her IOP remained elevated OU. She was referred to New York Eye and Ear Infirmary of Mount Sinai, where an LPI OS was performed, but angle-closure persisted, consistent with PIS. An ALPI OS with touch-up was performed, and her IOP normalized with dark-room gonioscopy revealing open angles OU.

Conclusions And importance

NPS has been associated with ocular hypertension (OHTN) and open-angle glaucoma (OAG); however, to our knowledge, no association between NPS and angle-closure has previously been reported. The case described here, of a patient with a rare de novo mutation and ocular findings of PIS with associated ACG, represents a novel genetic and clinical presentation of NPS.

A multistep approach to the diagnosis of rare genodermatoses

Genodermatoses are heritable skin diseases that can cause significant morbidity and mortality. Most of them show characteristic cutaneous findings. Genodermatoses can be associated with extracutaneous system abnormalities. Diagnosing hereditary skin disorders is still a challenging task due to their rarity and diversity, due to diseases evolving over many years, and the initial manifestations not always being diagnostic; therefore, ongoing evaluation and surveillance is often required to make the accurate diagnosis. The algorithm for the diagnosis depends on a combination of thorough clinical and family history clinical examination, laboratory findings, consultation of multiple medical specialists, and molecular analysis. Diagnostic testing targeted at differentiation of similar genodermatoses may be required. Recognition is crucial for the initiation of the treatment for skin manifestations and detection of other extracutaneous abnormalities, including malignancy. Diagnostic accuracy and molecular diagnosis may help in providing a template for ongoing management, testing, and education and prognostication for families of children with genodermatoses.

A Double Case of Nail-Patella Syndrome in the Same Family: The Importance of Nail Changes as Diagnostic Clues for Renal Involvement

Nail diseases are rarely given significant importance in general consultation and their specific examination is often neglected, while localization to the nails could be an initial sign of a syndrome or a systemic disorder. Although rarely, nail alterations could be a sign of a systemic disorder, in which a prompt observation is crucial for an early diagnosis. We describe the case of an elderly woman with a long history of nail dystrophy, previously labelled as nail fragility. On enquiry, similar nail changes were discovered to have affected the patient's son, who was visited the following week. Diagnosis of the Nail-Patella Syndrome (NPS) was suspected on the basis of nail alterations in both patients and confirmed by complementary radiographic examination. Screening for severe renal complications, which could have negatively affected the prognosis and have led to end-stage renal disease, followed. The prompt diagnosis of NPS and the associated diseases are mandatory for a correct management of these patients.

Hereditary Tumor Syndromes with Skin Involvement

Cutaneous findings that appear in childhood may be the first sign of a hereditary tumor syndrome. Early detection of genodermatoses allows the patient and at-risk family members to be screened for associated malignancies. This article provides a brief description of the pathogenesis and clinical manifestations of various inherited disorders with skin involvement, along with treatment updates. Advances in molecular-based therapy have spurred development of novel treatment methods for various genodermatoses such as xeroderma pigmentosum (XP) and Gorlin-Goltz syndrome. Further studies are needed to better assess the efficacy of many of these new treatment options.

Extracellular Matrix in Kidney Fibrosis: More Than Just a Scaffold

Kidney fibrosis is the common histological end-point of progressive, chronic kidney diseases (CKDs) regardless of the underlying etiology. The hallmark of renal fibrosis, similar to all other organs, is pathological deposition of extracellular matrix (ECM). Renal ECM is a complex network of collagens, elastin, and several glycoproteins and proteoglycans forming basal membranes and interstitial space. Several ECM functions beyond providing a scaffold and organ stability are being increasingly recognized, for example, in inflammation. ECM composition is determined by the function of each of the histological compartments of the kidney, that is, glomeruli, tubulo-interstitium, and vessels. Renal ECM is a dynamic structure undergoing remodeling, particularly during fibrosis. From a clinical perspective, ECM proteins are directly involved in several rare renal diseases and indirectly in CKD progression during renal fibrosis. ECM proteins could serve as specific non-invasive biomarkers of fibrosis and scaffolds in regenerative medicine. The gold standard and currently only specific means to measure renal fibrosis is renal biopsy, but new diagnostic approaches are appearing. Here, we discuss the localization, function, and remodeling of major renal ECM components in healthy and diseased, fibrotic kidneys and the potential use of ECM in diagnostics of renal fibrosis and in tissue engineering.

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.

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.

Brown tumor diagnosed three years after parathyroidectomy in a patient with nail-patella syndrome: A case report

We report a 48-year-old Japanese man with a brown tumor of the right distal tibia. At the age of 25 years, hemodialysis was initiated due to nail-patella syndrome. Severe secondary hyperparathyroidism and osteoporosis progressed over time, so parathyroidectomy was performed at age 45. Spontaneous fracture of the right distal tibia occurred suddenly at age 48. Imaging studies revealed a bone tumor-like lesion and surgery was performed. The resected specimen was a brown mass consisting of multinucleated giant cells on a fibrous tissue background, and these findings were consistent with a diagnosis of brown tumor. Immunohistochemistry revealed that multinucleated giant cells near areas of bone matrix were positive for tartrate-resistant acid phosphatase and cathepsin K, but the majority of the giant cells in the lesion were negative for these markers. Even after parathyroidectomy, brown tumor should be considered in the differential diagnosis of bone tumor-like lesions in patients on long-term dialysis. This case suggests that osteoclast activation may not contribute to development of brown tumors, although these lesions are generally considered to arise from subperiosteal bone resorption related to osteoclast overactivity in patients with hyperparathyroidism.

Total knee arthroplasty in a patient with nail-patella syndrome (NPS)

Nail-patella syndrome (NPS) or hereditary onycho-osteodyaplasia is a rare genetic condition involving a mutation in the LMX1B gene affecting nails, elbows, knees, and pelvis. Due to the regulatory functions of the gene in many developmental processes through the body, patients with NPS experience wide-ranging musculoskeletal problems including patellar instability, fingernail anomalies, iliac exostoses/horns, and elbow abnormalities. The patellar changes often involve aplasia, hypoplasia, and chronic dislocation. Due to these musculoskeletal involvement, arthritis of joints can occur in patients with NPS causing severe pain and disability. This is a case report of a patient with NPS who underwent a total knee arthroplasty for symptomatic knee arthritis.