Two novel recessive mutations in KRT14 identified in a cohort of 21 Spanish families with epidermolysis bullosa simplex.

BACKGROUND: Basal epidermolysis bullosa simplex (EBS) is a group of blistering genodermatoses mostly caused by mutations in the keratin genes, KRT5 and KRT14. Recessive mutations represent about 5% of all EBS mutations, being common and specific in populations with high consanguinity, where affected patients show severe phenotypes. OBJECTIVES: To accomplish the first mutational analysis in patients of Spanish origin with EBS and to delineate a comprehensive genotype-phenotype correlation. METHODS: Twenty-one EBS families were analysed. Immunofluorescence mapping at the dermoepidermal junction level was performed on skin biopsies from patients. Mutation screening of the entire coding sequences of KRT5 and KRT14 in genomic DNA was assessed by polymerase chain reaction and direct sequencing. RESULTS: KRT5 or KRT14 causative mutations were identified in 18 of the 21 EBS families. A total of 14 different mutations were disclosed, of which 12 were dominant missense mutations and two truncating recessive mutations. Five of the 14 mutations were novel including three dominant in KRT5 (p.V186E, p.T321P and p.A428T) and two recessive in KRT14 (p.K116X and p.K250RfsX8). The two patients with EBS carrying homozygous recessive mutations were affected by severe phenotypes and belonged to consanguineous families. All five families with the EBS Dowling-Meara subtype carried recurrent mutations affecting the highly conserved ends of the α-helical rod domain of K5 and K14. The seven mutations associated with the localized EBS subtype were widely distributed along the KRT5 and KRT14 genes. Two families with mottled pigmentation carried the P25L mutation in KRT5, commonly associated with this subtype. CONCLUSIONS: This study further confirms the genotype-phenotype correlation established for EBS in other ethnic groups, and is the first in a Mediterranean country (excluding Israel). This study adds two novel recessive mutations to the worldwide record to date, which includes a total of 14 mutations. As in previous reports, the recessive mutations resulted in a lack of keratin K14, giving rise to a generalized and severe presentation.

X-linked ichthyosis along with recessive dystrophic epidermolysis bullosa in the same patient.

X-linked ichthyosis (XLI) is a relatively common keratinization disorder which is caused, in the vast majority of cases, by a total deletion of the sulfatase steroid (STS) gene. Dystrophic epidermolysis bullosa (DEB) is a scarring form of epidermolysis bullosa of either autosomal recessive or dominant inheritance secondary to collagen VII gene mutations. We report the first case of a patient with both XLI and DEB in whom a partial deletion of the STS gene and a recessive point mutation in COL7A1 were demonstrated.

The first COL7A1 mutation survey in a large Spanish dystrophic epidermolysis bullosa cohort: c.6527insC disclosed as an unusually recurrent mutation.

BACKGROUND: Dystrophic epidermolysis bullosa (DEB) is a genodermatosis caused by mutations in COL7A1. The clinical manifestations are highly variable from nail dystrophy to life-threatening blistering, making early molecular diagnosis and prognosis of utmost importance for the affected families. Mutation identification is mandatory for prenatal testing. OBJECTIVES: To conduct the first mutational analysis of COL7A1 in a Spanish cohort, to assess mutation consequences at protein/mRNA level and to establish genotype-phenotype correlations. METHODS: Forty-nine Spanish patients with DEB were studied. Antigen mapping was performed on patient skin biopsies. COL7A1 mutation screening in genomic DNA was performed by polymerase chain reaction (PCR) and direct sequencing. Mutation consequences were determined by reverse transcriptase-PCR. RESULTS: Eight patients belonged to three unrelated families with dominant DEB. Forty-one were affected with recessive DEB (RDEB). Specifically, 27 displayed the severe generalized subtype, eight the other generalized subtype and six a localized phenotype (two pretibial, three acral and one inversa). Thirty-five mutations were identified, 20 of which are novel. The pathogenic mutation c.6527insC accounted for 46.3% of Spanish RDEB alleles. A consistent genotype-phenotype correlation was established. CONCLUSIONS: Although the COL7A1 database indicates that most DEB mutations are family specific, the pathogenic mutation c.6527insC was highly recurrent in our cohort. This level of recurrence for a single genetic defect has never previously been reported for COL7A1. Our findings are essential to the clinicians caring for patients with DEB in Spain and in the large population of Spanish descendants in Latin America. They also provide geneticists a molecular clue for a priority mutation screening strategy.

[Usefulness of the 14-3-3 test for the diagnosis of sCJD evaluated by a Spanish reference center]. / Utilidad del inmunoensayo de la proteína 14-3-3 en el diagnóstico de la enfermedad de Creutzfeldt-Jakob examinada desde un centro de referencia nacional.

INTRODUCTION: The performance of the 14-3-3 protein test has been shown to be adequate for sporadic Creutzfeldt-Jakob disease (sCJD) diagnosis in selected populations, but its routine validity has been questioned. METHODS: One thousand and sixty-eight patients with clinically suspected sCJD were analyzed in a Spanish reference center. In order to explore the influence of the clinical context on the performance of the immunoassay, the patients were classified at sample reception according to the World Health Organization (WHO) diagnostic criteria excluding the 14-3-3 test results. The yield of the immunoassay was evaluated in each subgroup with criteria of probable, possible sCJD or non-sCJD. RESULTS: In the set of patients with suspicion of sCJD the inclusion of the 14-3-3 test produces a significant increase in the diagnosis certainty (positive likelihood ratio: 10.1) compared to the WHO's criteria, excluding the 14-3-3 test. For patients classified at sample reception as probable sCJD (n=166), possible sCJD (n=129) and non-sCJD (n=773), the positive predictive values for the test were 98.4%, 97.5% and 31%, and the negative predictive values were 22.2%, 73.4% and 100%, respectively. CONCLUSIONS: The predictive values of the assay vary according to the previous diagnostic certainty. Therefore, in order to interpret correctly the test, it is necessary to evaluate the degree of initial clinical suspicion of the patient at the moment of the cerebrospinal fluid (CSF) extraction. This study offers up-to-date information, referenced to the Spanish population, and in useful format, and it is intended to serve as a guideline for 14-3-3 test results interpretation to the clinicians in our community.

Utilidad del inmunoensayo de la proteína 14-3-3 en el diagnóstico de la enfermedad de Creutzfeldt-Jakob examinada desde un centro de referencia nacional / Usefulness of the 14-3-3 test for the diagnosis of sCJD evaluated by a Spanish reference center

Introducción. El inmunoensayo de la proteína 14-3-3 en líquido cefalorraquídeo (LCR) muestra un rendimiento óptimo para el diagnóstico de la enfermedad de Creutzfeldt- Jakob esporádica (ECJe) en poblaciones seleccionadas, pero su validez en la práctica rutinaria ha sido cuestionada. Método. Se estudiaron 1.068 pacientes con sospecha de ECJe procedentes de distintas instituciones españolas. Para explorar la influencia del contexto clínico sobre la validez del inmunoensayo los pacientes fueron clasificados en el momento de la recepción de la muestra de acuerdo con los criterios de certeza diagnóstica establecidos por la Organización Mundial de la Salud (OMS), excluyendo la prueba de la proteína 14-3-3. El rendimiento del immunoensayo se evaluó en cada subgrupo con criterios de ECJe probable, posible o no ECJe. Resultados. En el conjunto de pacientes con sospecha de ECJe la inclusión del inmunoensayo supone un aumento significativo en la certeza diagnóstica (razón de verosimilitud positiva: 10,1) sobre los criterios de la OMS sin incluir dicha prueba. En los subgrupos de pacientes clasificados a la recepción de la muestra como ECJe probable (n=166), ECJe posible (n=129) y no ECJe (n=773) los valores predictivos positivos de la prueba de la proteína 14-3-3 fueron 98,4, 97,5 y 31% y los valores predictivos negativos fueron 22,2, 73,4 y 100%, respectivamente. Conclusiones. Los valores predictivos de la prueba varían según el grado de certeza diagnóstica previa de cada paciente. Por ello, para interpretar correctamente el ensayo es necesario valorar el grado de sospecha clínica del paciente en el momento de la extracción del LCR. Este estudio pretende facilitar la interpretación de los resultados de la prueba de la proteína 14-3-3 a los especialistas clínicos, ofreciendo una información actualizada, referenciada a la población española y en formato de utilidad práctica (AU)

Introduction: The performance of the 14-3-3 protein test has been shown to be adequate for sporadic Creutzfeldt-Jakob disease (sCJD) diagnosis in selected populations, but its routine validity has been questioned. Methods: One thousand and sixty-eight patients with clinically suspected sCJD were analyzed in a Spanish reference center. In order to explore the influence of the clinical context on the performance of the immunoassay, the patients were classified at sample reception according to the World Health Organization (WHO) diagnostic criteria excluding the 14-3-3 test results. The yield of the immunoassay was evaluated in each subgroup with criteria of probable, possible sCJD or non-sCJD. Results: In the set of patients with suspicion of sCJD the inclusion of the 14-3-3 test produces a significant increase in the diagnosis certainty (positive likelihood ratio: 10.1) compared to the WHO's criteria, excluding the 14-3-3 test. For patients classified at sample reception as probable sCJD (n=166), possible sCJD (n=129) and non-sCJD (n=773), the positive predictive values for the test were 98.4%, 97.5% and 31%, and the negative predictive values were 22.2%, 73.4% and 100%, respectively. Conclusions: The predictive values of the assay vary according to the previous diagnostic certainty. Therefore, in order to interpret correctly the test, it is necessary to evaluate the degree of initial clinical suspicion of the patient at the moment of the cerebrospinal fluid (CSF) extraction. This study offers up-to-date information, referenced to the Spanish population, and in useful format, and it is intended to serve as a guideline for 14-3-3 test results interpretation to the clinicians in our community (AU)

CSF analysis in patients with sporadic CJD and other transmissible spongiform encephalopathies.

Patients with suspected Creutzfeldt-Jakob disease (CJD) often have routine cerebrospinal fluid (CSF) analysis performed to exclude treatable inflammatory conditions; however, little information is available about the range of results obtained for CSF tests in patients with sporadic CJD and other transmissible spongiform encephalopathies (TSE). Data from 450 patients with sporadic CJD and 47 patients with other TSEs were collected as part of an EC-supported multinational study. Raised white cell counts of >5 cells/microl were found in three of 298 patients with sporadic CJD, with two cell counts of 7 cells/microl and one of 20 cells/microl. Total protein concentrations of >0.9 g/l were found in five of 438 patients with sporadic CJD, although none had a concentration of >1 g/l. CSF oligoclonal IgG was detected in eight of 182 sporadic CJD patients. Of the patients with other TSEs, six had elevated cell counts ranging from 6 to 14 cells/microl but none had total protein concentrations of >0.9 g/l and one patient had detectable oligoclonal IgG. None of the patients with sporadic CJD or other TSEs had abnormalities in all three tests.

CSF tests in the differential diagnosis of Creutzfeldt-Jakob disease.

OBJECTIVES: To analyze the diagnostic sensitivity and specificity of various brain-derived proteins (14-3-3, Tau, neuron specific enolase [NSE], and S100b) in the CSF of patients with Creutzfeldt-Jakob disease (CJD) and to analyze biologic factors that modify these parameters. METHODS: CSF was tested for 14-3-3, Tau, NSE, and S100b in 1,859 patients with sporadic, genetic, iatrogenic, and variant CJD, and in 1,117 controls. RESULTS: The highest sensitivity was achieved for 14-3-3 and Tau in sporadic CJD (85% and 86%), and a combined determination of 14-3-3 and Tau, S100b, or NSE increased the sensitivity to over 93%. A multivariate analysis showed that the sensitivity of all tests was highest in patients with the shortest disease duration, age at onset >40 years, and homozygosity at codon 129 of the prion protein gene. In a group of patients with repeated lumbar punctures, a second test also increased the diagnostic sensitivity. CONCLUSIONS: The detection of elevated levels of brain-derived proteins in the CSF in patients with suspected Creutzfeldt-Jakob disease is a valuable diagnostic test. A second lumbar puncture may be of value in patients with atypical clinical course in whom the first test was negative.

Determinants of diagnostic investigation sensitivities across the clinical spectrum of sporadic Creutzfeldt-Jakob disease.

To validate the provisional findings of a number of smaller studies and explore additional determinants of characteristic diagnostic investigation results across the entire clinical spectrum of sporadic Creutzfeldt-Jakob disease (CJD), an international collaborative study was undertaken comprising 2451 pathologically confirmed (definite) patients. We assessed the influence of age at disease onset, illness duration, prion protein gene (PRNP) codon 129 polymorphism (either methionine or valine) and molecular sub-type on the diagnostic sensitivity of EEG, cerebral MRI and the CSF 14-3-3 immunoassay. For EEG and CSF 14-3-3 protein detection, we also assessed the influence of the time point in a patient's illness at which the investigation was performed on the likelihood of a typical or positive result. Analysis included a large subset of patients (n = 743) in whom molecular sub-typing had been performed using a combination of the PRNP codon 129 polymorphism and the form of protease resistant prion protein [type 1 or 2 according to Parchi et al. (Parchi P, Giese A, Capellari S, Brown P, Schulz-Schaeffer W, Windl O, Zerr I, Budka H, Kopp N, Piccardo P, Poser S, Rojiani A, Streichemberger N, Julien J, Vital C, Ghetti B, Gambetti P, Kretzschmar H. Classification of sporadic Creutzfeldt-Jakob disease based on molecular and phenotypic analysis of 300 subjects. Ann Neurol 1999; 46: 224-233.)] present in the brain. Findings for the whole group paralleled the subset with molecular sub-typing data available, showing that age at disease onset and disease duration were independent determinants of typical changes on EEG, while illness duration significantly influenced positive CSF 14-3-3 protein detection; changes on brain MRI were not influenced by either of these clinical parameters, but overall, imaging data were less complete and consequently conclusions are more tentative. In addition to age at disease onset and illness duration, molecular sub-type was re-affirmed as an important independent determinant of investigation results. In multivariate analyses that included molecular sub-type, time point of the investigation during a patient's illness was found not to influence the occurrence of a typical or positive EEG or CSF 14-3-3 protein result. A typical EEG was most often seen in MM1 patients and was significantly less likely in the MV1, MV2 and VV2 sub-types, whereas VV2 patients had an increased likelihood of a typical brain MRI. Overall, the CSF 14-3-3 immunoassay was the most frequently positive investigation (88.1%) but performed significantly less well in the very uncommon MV2 and MM2 sub-types. Our findings confirm a number of determinants of principal investigation results in sporadic CJD and underscore the importance of recognizing these pre-test limitations before accepting the diagnosis excluded or confirmed. Combinations of investigations offer the best chance of detection, especially for the less common molecular sub-types such as MV2 and MM2.

Analysis of EEG and CSF 14-3-3 proteins as aids to the diagnosis of Creutzfeldt-Jakob disease.

OBJECTIVE: To improve diagnostic criteria for sporadic Creutzfeldt-Jakob disease (CJD). METHODS: Pooled data on initial and final diagnostic classification of suspected CJD patients were accumulated, including results of investigations derived from a coordinated multinational study of CJD. Prospective analysis for a comparison of clinical and neuropathologic diagnoses and evaluation of the sensitivity and specificity of EEG and 14-3-3 CSF immunoassay were conducted. RESULTS: Data on 1,003 patients with suspected CJD were collected using a standard questionnaire. After follow-up was carried out, complete clinical data and neuropathologic diagnoses were available in 805 cases. In these patients, the sensitivity of the detection of periodic sharp wave complexes in the EEG was 66%, with a specificity of 74%. The detection of 14-3-3 proteins in the CSF correlated with the clinical diagnosis in 94% (sensitivity). The specificity (84%) was higher than that of EEG. A combination of both investigations further increased the sensitivity but decreased the specificity. CONCLUSIONS: Incorporation of CSF 14-3-3 analysis in the diagnostic criteria for CJD significantly increases the sensitivity of case definition. Amended diagnostic criteria for CJD are proposed.

[Immunohistochemistry techniques in prion diseases]. / Técnicas de inmunohistoquímica en las enfermedades por priones.

The prion diseases are characterized by showing a broad spectrum of phenotypes with different clinical and neuropathological presentations. Detection of the prion protein is the marker used as a tool for making the definite diagnosis in these neurodegenerative diseases. Its presence may be detected by immunohistochemical and biochemical techniques. On immunohistochemical studies the prion protein shows three types of staining: as plaques of PrP-amyloid, perivascular and diffuse-synaptic.

[Neuropathology of the new variant of Creutzfeldt-Jakob disease]. / Neuropatología de la nueva variante de la enfermedad de Creutzfeldt-Jakob.

Identification in the United Kingdom of cases of Creutzfeldt-Jakob disease with clinical, genetic, neuropathological and phenotype characteristics different from those previously reported, together with its relation to bovine spongiform encephalopathy led to the establishment of a new condition known as a new variant of Creutzfeldt-Jakob disease. In this article we describe the neuropathology and immunohistochemistry of the prion protein involved.

Neuropatología de la nueva variante de la enfermedad de Creutzfeldt-Jakob / Neuropathology of the new variant of Creutzfeldt-Jakob disease

La identificación en el Reino Unido en 1996 de casos de enfermedad de Creutzfeldt-Jakob con características clínicas, genéticas, neuropatológicas y fenotípicas distintas a los demás casos detectados, así como su relación con la encefalopatía espongiforme bovina, supuso el establecimiento de una nueva entidad denominada nueva variante de enfermedad de Creutzfeldt-Jakob. En este artículo se lleva a cabo una descripción de su neuropatología y de la expresión de la proteína priónica a nivel inmunohistoquímico (AU)

Técnicas de inmunohistoquímica en las enfermedades por priones / Immunohistochemical techniques in prion diseases

Las enfermedades por priones se caracterizan por presentar un amplio espectro de fenotipos con diferentes presentaciones clínicas y neuropatológicas. La detección de la proteína priónica (PrP) es un marcador empleado como herramienta para realizar el diagnóstico definitivo de estas enfermedades neurodegenerativas. Su presencia puede observarse mediante técnicas de inmunohistoquímica y bioquímicas. A nivel inmunohistoquímico, la proteína priónica presenta principalmente tres tipos de patrones de tinción: en forma de placas de amiloide-PrP, perivacuolar y difusosináptico (AU)