A Search for Undiagnosed Charcot-Marie-Tooth Disease Among Patients Registered with Unspecified Polyneuropathy in the Danish National Patient Registry.

PURPOSE: In a recent study based on data from the Danish National Patients Registry (DNPR), we reported the prevalence of Charcot-Marie-Tooth disease (CMT) in Denmark to be 22.5 per 100.000. This prevalence is most likely a minimum estimate, as many cases of CMT may be misdiagnosed or remain undiagnosed due to the heterogeneous nature of the disorder. The aim of this study was to investigate the possible number of undiagnosed CMT cases among patients registered with unspecified polyneuropathy (UP) diagnoses in the DNPR. PATIENTS AND METHODS: From the DNPR we extracted data on all patients given an UP diagnosis in the period 1977 to 2012. We selected all patients diagnosed with a primary UP diagnosis before age 40 at a department of neurology, neurophysiology, clinical genetics or pediatrics, and excluded all patients with a specified polyneuropathy diagnosis or with diagnostic codes related to alcohol and diabetes mellitus. To assess the proportion of possible CMT patients, we performed medical record review in a random sample of patients diagnosed in the Central Denmark Region. To further investigate the possible overlap between UP and CMT in the DNPR, we performed a series of searches for ICD-8 and ICD-10 codes related to CMT. RESULTS: Between 1977 and 2012, 30.903 patients were diagnosed with UP without also being diagnosed with CMT. A total of 940 patients fulfilled the selection criteria. We found that 21.5% (95% CI 13.1%-32.2%) of the cases in the random sample fulfilled our criteria for CMT. This estimate increases the prevalence of CMT in Denmark with 3.6 per 100,000 (95% CI 2.4%-5.5%). CONCLUSION: This study illustrates how hitherto undiagnosed CMT patients may be identified in the DNPR and further reports the number of possible CMT cases. Our results support the hypothesis that the true prevalence of CMT is higher than recently reported.

Genetic analysis of Charcot-Marie-Tooth disease in Denmark and the implementation of a next generation sequencing platform.

Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of hereditary polyneuropathies. Variants in more than 80 different genes have been associated with the disorder. In recent years, the introduction of next generation sequencing (NGS) techniques have completely changed the genetic diagnostic approach from the analysis of a handful of genes to the analysis of all genes associated with CMT in a single run. In this study we describe the CMT diagnostics in Denmark in 1992-2012, prior to the implementation of NGS, by combining laboratory- and national registry data. We investigate the effect of implementing a targeted NGS approach of 63 genes associated with CMT in the diagnostic laboratory setting. This was performed by analyzing a cohort of 195 samples from patients previously analyzed by Sanger sequencing and quantitative analysis for the common causes of CMT without reaching a molecular diagnosis. A total of 1442 CMT analyses were performed in Denmark in the period 1992-2012; a disease-causing variant was detected in 21.6% of the cases. Interestingly, the diagnosis was genetically confirmed in significantly more women than men; 25.9% compared to18.5%. In our study cohort, we found a 5.6% increase in the diagnostic yield with the introduction of a targeted NGS approach.

Charcot-Marie-Tooth disease in Denmark: a nationwide register-based study of mortality, prevalence and incidence.

OBJECTIVES: Charcot-Marie-Tooth disease (CMT) is the most common inherited disorder of the peripheral nervous system, yet no studies have compared the mortality in patients with CMT with that of the general population, and prevalence estimates vary considerably. We performed a nationwide register-based study to investigate the prevalence, incidence and mortality of CMT in Denmark. DESIGN: We used the Danish National Patient Registry to select all records with primary diagnostic codes for CMT between 1977 and 2012 given at a neurological, neurophysiological, paediatric or clinical genetic clinic. The prevalence was estimated by 31 December 2012, and the incidence rate was calculated based on data from 1988 to 2012. We calculated a standardised mortality ratio (SMR) and an absolute excess mortality rate (AER) stratified according to age categories and disease duration. RESULTS: A total of 1534 patients (652 women) were identified. The prevalence proportion was 22.5 per 100 000 (95% CI 21.2 to 23.7) and the incidence rate was 0.98 (95% CI 0.93 to 1.04) per 100 000 person-years. The SMR was 1.36 (95% CI 1.21 to 1.53), and the AER was 4.87 per 1000 person-years (95% CI 2.77 to 6.96). We found a significantly higher SMR in cases below 50 years of age, and in cases with disease duration of more than 10 years. CONCLUSIONS: We found a reduced life expectancy among patients diagnosed with CMT. To our knowledge, this is the first study of CMT to use nationwide register-based data, and the first to report an SMR and an AER.

Magnetic resonance neurography and diffusion tensor imaging of the peripheral nerves in patients with Charcot-Marie-Tooth Type 1A.

INTRODUCTION: Investigation of peripheral neuropathies by magnetic resonance neurography (MRN) may provide increased diagnostic accuracy when performed in combination with diffusion tensor imaging (DTI). This study seeks to evaluate DTI in the detection of neuropathic abnormalities in Charcot-Marie-Tooth type 1A (CMT1A). METHODS: MRI of the sciatic and tibial nerves, including MRN and DTI, was prospectively performed in 15 CMT1A patients and 30 healthy controls (HCs). The following MRI parameters were evaluated and correlated with clinical and neurophysiological findings: T2-relaxation time, proton spin density (PD) and DTI (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]). RESULTS: DTI showed lower FA and higher ADC in CMT1A compared with HCs. T2 relaxation time showed no difference; however, PD of the sciatic nerve was higher in CMT1A. There were some close associations between neuropathy severity and MRN-DTI, with the closest correlation between FA and nerve conduction velocity in the sciatic nerve (r = 0.76, P < 0.01). DISCUSSION: MRN-DTI evaluation of sciatic and tibial nerves improves the detection of nerve abnormalities in patients with CMT1A. Muscle Nerve 56: E78-E84, 2017.

Validation of diagnostic codes for Charcot-Marie-Tooth disease in the Danish National Patient Registry.

PURPOSE: To validate the diagnostic codes for Charcot-Marie-Tooth disease (CMT) in the Danish National Patient Registry (DNPR) using positive predictive value (PPV) as a measure of validity. PATIENTS AND METHODS: We used the DNPR to identify all patients diagnosed with at least one primary CMT diagnosis at a specialized department in the Central Denmark Region during the period 1977-2012. From this population, we randomly selected 123 patients for the validation study. Medical files were reviewed and used as reference standard. We estimated the PPV of the CMT diagnoses and stratified the analysis according to age at diagnosis, gender, and calendar time. RESULTS: In the DNPR, 275 patients were identified. We were able to retrieve 96 medical files from the random sample of 123 patients, and 85 CMT diagnoses were confirmed. The average age at diagnosis was 42.5 years, and 34% were female. The PPV was 88.5% (95% confidence interval: 80.4-94.1). CONCLUSION: The CMT diagnoses in the DNPR have high validity. The DNPR can be used as a data source for epidemiologic research on CMT.

Rothmund-Thomson Syndrome: novel pathogenic mutations and frequencies of variants in the RECQL4 and USB1 (C16orf57) gene.

BACKGROUND: Poikiloderma is defined as a chronic skin condition presenting with a combination of punctate atrophy, areas of depigmentation, hyperpigmentation and telangiectasia. In a variety of hereditary syndromes such as Rothmund-Thomson syndrome (RTS), Clericuzio-type poikiloderma with neutropenia (PN) and Dyskeratosis Congenita (DC), poikiloderma occurs as one of the main symptoms. Here, we report on genotype and phenotype data of a cohort of 44 index patients with RTS or related genodermatoses. METHODS: DNA samples from 43 patients were screened for variants in the 21 exons of the RECQL4 gene using PCR, SSCP-PAGE analysis and/or Sanger sequencing. Patients with only one or no detectable mutation in the RECQL4 gene were additionally tested for variants in the 8 exons of the USB1 (C16orf57) gene by Sanger sequencing. The effect of novel variants was evaluated by phylogenic studies, single-nucleotide polymorphism (SNP) databases and in silico analyses. RESULTS: We identified 23 different RECQL4 mutations including 10 novel and one homozygous novel USB1 (C16orf57) mutation in a patient with PN. Moreover, we describe 31 RECQL4 and 8 USB1 sequence variants, four of them being novel intronic RECQL4 sequence changes that may have some deleterious effects on splicing mechanisms and need further evaluation by transcript analyses. CONCLUSION: The current study contributes to the improvement of genetic diagnostic strategies and interpretation in RTS and PN that is relevant in order to assess the patients' cancer risk, to avoid continuous and inconclusive clinical evaluations and to clarify the recurrence risk in the families. Additionally, it shows that the phenotype of more than 50% of the patients with suspected Rothmund-Thomson disease may be due to mutations in other genes raising the need for further extended genetic analyses.

A novel single nucleotide splice site mutation in FHL1 confirms an Emery-Dreifuss plus phenotype with pulmonary artery hypoplasia and facial dysmorphology.

We describe a Danish family with an, until recently, unknown X-linked disease with muscular dystrophy (MD), facial dysmorphology and pulmonary artery hypoplasia. One patient died suddenly before age 20 and another was resuscitated from cardiac arrest at the age of 28. Linkage analysis pointed to a region of 25 Mb from 123.6 Mb to 148.4 Mb on chromosome X containing over 100 genes. Exome sequencing identified a single nucleotide splice site mutation c.502-2A > T, which is located 5' to exon 6 in the gene encoding four and a half LIM domain 1 (FHL1) protein. FHL1 expresses three main splice variants, known as FHL1A, FHL1B and FHL1C. In healthy individuals, FHL1A is the predominant splice variant and is mainly found in skeletal and cardiac muscle. The FHL1 transcript profiles from two affected individuals were investigated in skin fibroblasts with quantitative real-time PCR. This demonstrated loss of isoform A and B, and an almost 200-fold overexpression of isoform C confirming that lack of FHL1A and overexpression of FHL1C results in an extended phenotype of EDMD as recently shown by Tiffin et al. [2013].

Epstein-Barr virus infection leads to partial phenotypic reversion of terminally differentiated malignant B cells.

The B cell lymphomas associated with Epstein-Barr virus (EBV) are not limited to any specific stage of B cell differentiation but covers widely different B cell phenotypes. In vitro infection of the virus negative tumors with a recombinant EBV strain has provided important insights into virus-tumor interaction. Here, we investigated the interaction between EBV and terminally differentiated tumor derived B cells, namely multiple myeloma (MM). The in vitro EBV infected MM expressed restricted viral latency. Acquisition of the virus was accompanied by a partial reprogramming to a mature B cell phenotype. Thus, the plasma cell markers syndecan-1 (CD138), Blimp1 and MUM1 were downregulated, while expression of HLADR, CIITA and TCL1, which are normally not expressed in plasmacytoid cells, was upregulated. The silenced transcription factor gene encoding Pax5 and its target BLNK were activated. Significantly, the free lambda light chains secreted in the medium were reduced in EBV infected MM clones. Collectively, these results suggest that the restricted EBV latency can cause at least partial phenotypic reversion of terminally differentiated B tumor cells. We suggest that the restricted EBV latent gene expression may not only be the consequence but the cause of the mature B cell phenotype, actively participating in the virus persistence.