Management of patellar problems in skeletally mature patients with nail-patella syndrome.

PURPOSE: Nail-patella syndrome (NPS) or hereditary onychoosteodysplasia is a rare autosomal dominant disease, characterized by a tetrad of findings, which include fingernail abnormalities, hypoplasia of the patellae, radial head dislocation and prominent iliac horns. Most of the literature on the treatment of patellar problems in NPS concerns paediatric patients, and there is no standard treatment algorithm for adult patients. METHODS: We reviewed the charts of skeletally mature patients with NPS who presented to our clinic. We reviewed the presenting complaints, the physical examination findings and the radiographic imaging. RESULTS: We identified seven skeletally mature patients with NPS who presented with patellofemoral complaints. Their symptoms were instability, pain, or a combination of the two. Examination and imaging revealed a wide range of severity but included patellar instability and patellar arthritis. In our series, milder forms of the disease were treated with non-operative measures, but the majority of our patients required surgery including medial patellofemoral ligament reconstruction, tibial tuberosity transposition, patellofemoral and total knee arthroplasty. At midterm follow-up, most patients had good results. CONCLUSION: Nail-patella syndrome has a wide range of presentations and severity in skeletally mature patients. Knee surgeons should be familiar with the spectrum of clinical presentation and the range of treatment options available in order to provide optimum treatment for patients with this disorder. LEVEL OF EVIDENCE: IV.

c.194 A>C (Q65P) mutation in the LMX1B gene in patients with nail-patella syndrome associated with glaucoma.

PURPOSE: To report the clinical, ophthalmic, extraophthalmic, and genetic characteristics of nail-patella syndrome (NPS) in a Chilean family and to investigate the expressivity of open angle glaucoma (OAG) and ocular hypertension (OHT) in the family members. METHODS: Five family members affected with NPS and two unaffected members underwent a complete ophthalmologic examination, including computerized visual field, optical coherence tomography (OCT) of the optic disc and ultrasound pachymetry. Renal function was assessed by urinalysis and blood tests. Orthopedic evaluations were also performed, including radiological studies of the wrist, elbow and hip joints. Genomic DNA was extracted from peripheral leukocytes of the five affected and two unaffected family members. Exons 2-6 of the LIM homeobox transcription factor 1-beta (LMX1B) gene were screened for mutations by DNA sequencing of the proband. We also screened for mutations in exon 2 by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the other participants and 91 blood donors. RESULTS: Five living family members from three generations were positively diagnosed with NPS, three of them with varying degrees of OAG and one with OHT. Retinal nerve fiber layer (RNFL) thickness measured by spectral domain OCT was below normal values in three individuals. All subjects evaluated had normal nephrologic function. Orthopedic, clinical, and radiological alterations were compatible with NPS. Screening for mutations in exons 2- 6 of LMX1B showed a heterozygous missense mutation c.194 A>C changing glutamine to proline within exon 2 in codon 65 (Q65P) of the coding sequence. This mutation was present in all NPS subjects and absent in the unaffected family members and in 91 Chilean blood donors. CONCLUSIONS: This is the first report of c.194 A>C mutation in LMX1B in a Chilean family with NPS and the second worldwide. The phenotype associated with this mutation is variable within the family, although we noted a close connection between the presence of the c.194 A>C mutation and the presence of OHT or OAG and probably also with an early onset of OHT in patients with NPS. All subjects older than 21 years had either OHT or OAG. We also suggest that the LMX1B mutation may be related to affective disorders.

Glomerular basement membrane disorders in experimental models for renal diseases: impact on understanding pathogenesis and improving diagnosis.

Animal models have provided important insights into human renal diseases that arise from mutations in genes that encode or regulate the synthesis of glomerular basement membrane proteins. This chapter describes several well-characterized animal models of type IV collagen disorders (Alport syndrome, HANAC syndrome), a laminin disorder (Pierson syndrome), nail-patella syndrome and HERNS syndrome. These models can be exploited in studies of the pathogenesis and treatment of such disorders.

Clinico-genetic study of nail-patella syndrome.

Nail-patella syndrome (NPS) is an autosomal dominant disease that typically involves the nails, knees, elbows and the presence of iliac horns. In addition, some patients develop glomerulopathy or adult-onset glaucoma. NPS is caused by loss-of-function mutations in the LMX1B gene. In this study, phenotype-genotype correlation was analyzed in 9 unrelated Korean children with NPS and their affected family members. The probands included 5 boy and 4 girls who were confirmed to have NPS, as well as 6 of their affected parents. All of the patients (100%) had dysplastic nails, while 13 patients (86.7%) had patellar anomalies, 8 (53.3%) had iliac horns, 6 (40.0%) had elbow contracture, and 4 (26.7%) had nephropathy including one patient who developed end-stage renal disease at age 4.2. The genetic study revealed 8 different LMX1B mutations (5 missense mutations, 1 frame-shifting deletion and 2 abnormal splicing mutations), 6 of which were novel. Genotype-phenotype correlation was not identified, but inter- and intrafamilial phenotypic variability was observed. Overall, these findings are similar to the results of previously conducted studies, and the mechanism underlying the phenotypic variations and predisposing factors of the development and progression of nephropathy in NPS patients are still unknown.

Multiple triangular lunula unguis: a specific finding for the nail-patella syndrome.

In this case presentation recognition of multiple triangular lunula unguis led to the diagnosis of the rare nail-patella syndrome (NPS). A single triangular lunula may be traumatic in origin, but multiple, with apex pointing toward the free edge of the nail, must be considered part of the NPS especially when combined with absence of the distal interphalangeal joint creases.

Genotype-phenotype studies in nail-patella syndrome show that LMX1B mutation location is involved in the risk of developing nephropathy.

Nail-patella syndrome (NPS) is characterized by developmental defects of dorsal limb structures, nephropathy, and glaucoma and is caused by heterozygous mutations in the LIM homeodomain transcription factor LMX1B. In order to identify possible genotype-phenotype correlations, we performed LMX1B mutation analysis and comprehensive investigations of limb, renal, ocular, and audiological characteristics in 106 subjects from 32 NPS families. Remarkable phenotypic variability at the individual, intrafamilial, and interfamilial level was observed for different NPS manifestations. Quantitative urinanalysis revealed proteinuria in 21.3% of individuals. Microalbuminuria was detected in 21.7% of subjects without overt proteinuria. Interestingly, nephropathy appeared significantly more frequent in females. A significant association was established between the presence of clinically relevant renal involvement in an NPS patient and a positive family history of nephropathy. We identified normal-tension glaucoma (NTG) and sensorineural hearing impairment as new symptoms associated with NPS. Sequencing of LMX1B revealed 18 different mutations, including six novel variants, in 28 families. Individuals with an LMX1B mutation located in the homeodomain showed significantly more frequent and higher values of proteinuria compared to subjects carrying mutations in the LIM domains. No clear genotype-phenotype association was apparent for extrarenal manifestations. This is the first study indicating that family history of nephropathy and mutation location might be important in precipitating individual risks for developing NPS renal disease. We suggest that the NPS phenotype is broader than previously described and that NTG and hearing impairment are part of NPS. Further studies on modifier factors are needed to understand the mechanisms underlying phenotypic heterogeneity.

Nail-patella syndrome: identification of mutations in the LMX1B gene in Dutch families.

Nail-patella syndrome is an autosomal dominant disorder characterized by dyplasia of finger nails, skeletal anomalies, and, frequently, renal disease. It has recently been shown that this disorder is caused by putative loss-of-function mutations in a transcription factor (LMX1B) belonging to the LIM-homeodomain family, members of which are known to be important for pattern formation during development. A cohort of eight Dutch NPS families were screened for mutations in the LMX1B gene; seven different mutations, including one novel variant, were identified. Three of the mutations are very likely to result in truncated LMX1B proteins, three are predicted to influence sequence-specific DNA binding, and one is presumed to prevent the formation of a stable protein by abolishing the Zn(II) binding site of the protein. Although there was a remarkable high incidence of renal disease in one of the families, the nephropathy was not seen in all affected family members and the severity of renal impairment varied significantly among the patients. This indicates that the incidence and severity of nephropathy within this family cannot be attributed to the LMX1B genotype. In addition, evidence of a correlation between other characteristics of the NPS phenotype and specific mutations has not been found.

Loss-of-function mutations in the LIM-homeodomain gene, LMX1B, in nail-patella syndrome.

Nail-patella syndrome (NPS) is an inherited developmental disorder most commonly involving maldevelopment of the fingernails, kneecaps and elbow joints. NPS exhibits wide variation in phenotypic expression within and among families with respect to these features. Other skeletal abnormalities such as hip dislocation and club foot have also been reported in some individuals with NPS. There is an association between NPS and renal disease, and between NPS and open-angle glaucoma (OAG), but it is not known whether mutations in a single gene cause the observed skeletal, renal and ophthalmic abnormalities. Recently, LMX1B , a transcription factor of the LIM-homeodomain type with homologs that are important for limb development in vertebrates, was mapped to the same general location as NPS at 9q34. We sequenced a large segment of LMX1B from the genomic DNA of probands from four families with NPS and OAG, and identified four mutations: two stop codons, a deletion causing a frameshift and a missense mutation in a functionally important residue. The presence of these putative loss-of-function mutations in the DNA of individuals with NPS indicates that haploinsufficiency of LMX1B underlies this disorder. These findings help to explain the high degree of variability in the NPS phenotype, and suggest that the skeletal defects in NPS are a result of the diminished dorsoventral patterning activity of LMX1B protein during limb development. The results further suggest that the NPS and OAG phenotypes in the families studied result from mutations in a single gene, LMX1B.

Nephropathy of nail-patella syndrome.

Ultrastructural renal lesions of a sporadic case of nail-patella syndrome are described. Although the patient, an 8-year-old Japanese boy, had no clinical renal syndrome, electron microscopy disclosed the presence of collagen fibrils and electron lucent areas within glomerular basement membrane. Comparative observation of glomeruli in sections stained by uranyl-acetate and lead-citrate and those by PTAH-uranyl revealed evidence of many collagen fibrils in mesangial matrix, as well as glomerular basement membrane. At the follow-up study 3 years after the biopsy, he still showed normal urinalysis and no renal dysfunction. Characteristic ultrastructure of glomerulus of this disease can be present even in cases without any apparent clinical renal involvement. It is concluded that the glomerular lesions in nail-patella syndrome may be caused by abnormal metabolic processes of collagen in glomeruli rather than entrapment of circulating collagen precursors.