Neurofibromatosis without Neurofibromas: Confirmation of a Genotype-Phenotype Correlation and Implications for Genetic Testing

Neurofibromatosis type 1 (NF1) is a multisystem disease with autosomal dominant inheritance and complete penetrance diagnosed by clinical findings. Cutaneous neurofibromas are present in almost all adult patients in the dermis, epidermis or along the peripheral nerves. Plexiform neurofibromas are subcutaneous or deep lesions involving nerve plexuses or roots. Neurofibromas can degenerate into malignant tumors, with important prognostic implications. NF1 shows a broad clinic variability even within a single family. Exceptions are cases reporting the in-frame microdeletion c.2970_2972delAAT, presenting with the typical pigmentary features of NF1, but no cutaneous or plexiform neurofibromas. We report a patient with a de novo c.2970_2972delAAT mutation who had few café-au-lait spots, only 2 of which measured >15 mm, axillary and submammary freckling, a flat angioma extending over the neck, arm and trunk, a high arched palate, micrognathia, macrocephaly, pes cavus and scoliosis. There was complete absence of observable cutaneous neurofibromas as well as external plexiform neurofibromas. She had had epileptic seizures since childhood; however, a diagnosis of NF1 had not been confirmed until she was 38, partly due to the paucity of characteristic cutaneous stigmata. We confirm the association of the c.2970_2972delAAT mutation in NF1 with a particular clinical phenotype, especially with lack of detectable neurofibromas. For an appropriate management of patients and family counseling, molecular study of the NF1 gene should be considered in patients not fulfilling NIH criteria when other features suggestive of NF1 are present. In the absence of neurofibromas, starting NF1 testing with the screening of exon 17 may be worthwhile

Assessment of plasma chitotriosidase activity, CCL18/PARC concentration and NP-C suspicion index in the diagnosis of Niemann-Pick disease type C: A prospective observational study

Background: Niemann-Pick disease type C (NP-C) is a rare, autosomal recessive neurodegenerative disease caused by mutations in either the NPC1 or NPC2 genes. The diagnosis of NP-C remains challenging due to the non-specific, heterogeneous nature of signs/symptoms. This study assessed the utility of plasma chitotriosidase (ChT) and Chemokine (C-C motif) ligand 18 (CCL18)/pulmonary and activation-regulated chemokine (PARC) in conjunction with the NP-C suspicion index (NP-C SI) for guiding confirmatory laboratory testing in patients with suspected NP-C. Methods: In a prospective observational cohort study, incorporating a retrospective determination of NP-C SI scores, two different diagnostic approaches were applied in two separate groups of unrelated patients from 51 Spanish medical centers (n = 118 in both groups). From Jan 2010 to Apr 2012 (Period 1), patients with =2 clinical signs/symptoms of NP-C were considered ''suspected NP-C'' cases, and NPC1/NPC2 sequencing, plasma chitotriosidase (ChT), CCL18/PARC and sphingomyelinase levels were assessed. Based on findings in Period 1, plasma ChT and CCL18/PARC, and NP-C SI prediction scores were determined in a second group of patients between May 2012 and Apr 2014 (Period 2), and NPC1 and NPC2 were sequenced only in those with elevated ChT and/or elevated CCL18/PARC and/or NP-C SI =70. Filipin staining and 7-ketocholesterol (7-KC) measurements were performed in all patients with NP-C gene mutations, where possible. Results: In total across Periods 1 and 2, 10/236 (4%) patients had a confirmed diagnosis o NP-C based on gene sequencing (5/118 4.2%] in each Period): all of these patients had two causal NPC1 mutations. Single mutant NPC1 alleles were detected in 8/236 (3%) patients, overall. Positive filipin staining results comprised three classical and five variant biochemical phenotypes. No NPC2 mutations were detected. All patients with NPC1 mutations had high ChT activity, high CCL18/PARC concentrations and/or NP-C SI scores =70. Plasma 7-KC was higher than control cut-off values in all patients with two NPC1 mutations, and in the majority of patients with single mutations. Family studies identified three further NP-C patients. Conclusion: This approach may be very useful for laboratories that do not have mass spectrometry facilities and therefore, they cannot use other NP-C biomarkers for diagnosis

Spinocerebellar ataxia 36 (SCA36): “Costa da Morte ataxia”

Introduction-objective: To describe the history of the discovery of SCA36 and review knowledge of this entity, which is currently the most prevalent hereditary ataxia in Galicia (Spain) owing to a founder effect. Development: SCA36 is an autosomal dominant hereditary ataxia with late onset and slow progression. It presents with cerebellar ataxia, sensorineural hearing loss, and discrete motor neuron impairment (tongue atrophy with denervation, discrete pyramidal signs). SCA36 was first described in Japan (Asida River ataxia) and in Galicia (Costa da Morte ataxia). The condition is caused by a genetic mutation (intronic hexanucleotide repeat expansion) in the NOP56 gene on the short arm of chromosome 20 (20p13). Magnetic resonance image study initially shows cerebellar vermian atrophy that subsequently extends to the rest of the cerebellum and finally to the pontomedullary region of the brainstem without producing white matter lesions. Peripheral nerve conduction velocities are normal, and sensorimotor evoked potential studies show delayed conduction of stimuli to lower limbs. In patients with hearing loss, audiometric studies show a drop of >40 dB in frequencies exceeding 2500 Hz. Auditory evoked potential studies may also show lack of waves I and II. Conclusions: Costa da Morte ataxia or SCA36 is the most prevalent SCA in the Spanish region of Galicia. Given the region's history of high rates of emigration, new cases may be diagnosed in numerous countries, especially in Latin America. Genetic studies are now available to patients and asymptomatic carriers. Since many people are at risk for this disease, we will continue our investigations aimed at elucidating the underlying pathogenic molecular mechanisms and discovering effective treatment. Resumen: Introducción-objetivos: Describir la historia del descubrimiento de la SCA36 y revisar los conocimientos actuales sobre esta entidad que, por un efecto fundador, ha pasado a ser la SCA más prevalente en Galicia (España). Desarrollo: La SCA36 es una enfermedad heredodegenerativa autosómica dominante, de inicio tardío y lenta progresión, que cursa con ataxia cerebelosa, hipoacusia neurosensorial y discreta afectación de neuronas motoras (atrofia y fasciculaciones linguales y signos piramidales leves). Ha sido descrita inicialmente en Japón (ataxia del río Asida) y en Galicia (ataxia da Costa da Morte). Se produce por una mutación (expansión intrónica de hexanucleótido) en el gen NOP56, localizado en 20p13. En los estudios de resonancia magnética se observa inicialmente atrofia vermiana superior, que se extenderá al resto del cerebelo y finalmente a la porción bulboprotuberancial del tronco cerebral, sin lesiones de sustancia blanca. Las velocidades de conducción nerviosa periférica son normales y en los estudios de potenciales evocados somatosensoriales se detecta retraso de la conducción al estimular en miembros inferiores. En los pacientes con hipoacusia, suele encontrarse en la audiometría una caída > 40 dB a partir de 2.400 Hz; también se observa ausencia de ondas i y ii en los estudios de potenciales evocados auditivos. Conclusiones: La ataxia da Costa da Morte-SCA36 es la SCA más prevalente en Galicia (España). Dada la alta tasa de emigración de nuestra comunidad autónoma, se espera que se diagnostiquen nuevos casos en diversas latitudes, sobre todo en América Latina. Ahora está disponible el diagnóstico genético para pacientes con clínica y portadores asintomáticos. Dado el alto número de pacientes en riesgo de sufrir la enfermedad, continuamos con las investigaciones para aclarar los mecanismos moleculares patogénicos y poder encontrar una terapéutica. Keywords: Hereditary ataxias, Spinocerebellar ataxia type 36, NOP56, Hexanucleotide expansion, Costa da Morte ataxia, Palabras clave: Heredoataxias, Ataxia espinocerebelosa tipo 36, NOP56, Expansión de hexanucleótido, Ataxia da Costa da Mort

Variations in the Genome: The Mutation Detection 2015 Meeting on Detection, Genome Sequencing, and Interpretation

Molecular Technology and Informatics for Personalised Medicine and Healt

La ataxia espinocerebelosa 36 (SCA36): «Ataxia da Costa da Morte»

Resumen: Introducción-objetivos: Describir la historia del descubrimiento de la SCA36 y revisar los conocimientos actuales sobre esta entidad que, por un efecto fundador, ha pasado a ser la SCA más prevalente en Galicia (España). Desarrollo: La SCA36 es una enfermedad heredodegenerativa autosómica dominante, de inicio tardío y lenta progresión, que cursa con ataxia cerebelosa, hipoacusia neurosensorial y discreta afectación de neuronas motoras (atrofia y fasciculaciones linguales y signos piramidales leves). Ha sido descrita inicialmente en Japón (ataxia del río Asida) y en Galicia (ataxia da Costa da Morte). Se produce por una mutación (expansión intrónica de hexanucleótido) en el gen NOP56, localizado en 20p13. En los estudios de resonancia magnética se observa inicialmente atrofia vermiana superior, que se extenderá al resto del cerebelo y finalmente a la porción bulboprotuberancial del tronco cerebral, sin lesiones de sustancia blanca. Las velocidades de conducción nerviosa periférica son normales y en los estudios de potenciales evocados somatosensoriales se detecta retraso de la conducción al estimular en miembros inferiores. En los pacientes con hipoacusia, suele encontrarse en la audiometría una caída > 40 dB a partir de 2.400 Hz; también se observa ausencia de ondas i y ii en los estudios de potenciales evocados auditivos. Conclusiones: La ataxia da Costa da Morte-SCA36 es la SCA más prevalente en Galicia (España). Dada la alta tasa de emigración de nuestra comunidad autónoma, se espera que se diagnostiquen nuevos casos en diversas latitudes, sobre todo en América Latina. Ahora está disponible el diagnóstico genético para pacientes con clínica y portadores asintomáticos. Dado el alto número de pacientes en riesgo de sufrir la enfermedad, continuamos con las investigaciones para aclarar los mecanismos moleculares patogénicos y poder encontrar una terapéutica. Abstract: Introduction-objective: To describe the history of the discovery of SCA36 and review knowledge of this entity, which is currently the most prevalent hereditary ataxia in Galicia (Spain) owing to a founder effect. Development: SCA36 is an autosomal dominant hereditary ataxia with late onset and slow progression. It presents with cerebellar ataxia, sensorineural hearing loss, and discrete motor neuron impairment (tongue atrophy with denervation, discrete pyramidal signs). SCA36 was first described in Japan (Asida River ataxia) and in Galicia(Costa da Morte ataxia). The condition is caused by a genetic mutation (intronic hexanucleotide repeat expansion) in the NOP56 gene on the short arm of chromosome 20 (20p13). Magnetic resonance image study initially shows cerebellar vermian atrophy that subsequently extends to the rest of the cerebellum and finally to the pontomedullary region of the brainstem without producing white matter lesions. Peripheral nerve conduction velocities are normal, and sensorimotor evoked potential studies show delayed conduction of stimuli to lower limbs. In patients with hearing loss, audiometric studies show a drop of > 40 dB in frequencies exceeding 2,500 Hz. Auditory evoked potential studies may also show lack of waves I and II. Conclusions: Costa da Morte ataxia or SCA36 is the most prevalent SCA in the Spanish region of Galicia. Given the region's history of high rates of emigration, new cases may be diagnosed in numerous countries, especially in Latin America. Genetic studies are now available to patients and asymptomatic carriers. Since many people are at risk for this disease, we will continue our investigations aimed at elucidating the underlying pathogenic molecular mechanisms and discovering effective treatment. Palabras clave: Heredoataxias, Ataxia espinocerebelosa tipo 36, NOP56, Expansión de hexanucleótido, Ataxia da Costa da Morte, Keywords: Hereditary ataxias, Spinocerebellar ataxia type 36, NOP56, Hexanucleotide expansion, Costa da Morte ataxi

Medical genomics: The intricate path from genetic variant identification to clinical interpretation

The field of medical genomics involves translating high throughput genetic methods to the clinic, in order to improve diagnostic efficiency and treatment decision making. Technical questions related to sample enrichment, sequencing methodologies and variant identification and calling algorithms, still need careful investigation in order to validate the analytical step of next generation sequencing techniques for clinical applications. However, the main foreseeable challenge will be interpreting the clinical significance of the variants observed in a given patient, as well as their significance for family members and for other patients. Every step in the variant interpretation process has limitations and difficulties, and its quote of contribution to false positive and false negative results. There is no single piece of evidence enough on its own to make firm conclusions on the pathogenicity and disease causality of a given variant. A plethora of automated analysis software tools is being developed that will enhance efficiency and accuracy. However a risk of misinterpretation could derive from biased biorepository content, facilitated by annotation of variant functional consequences using previous datasets stored in the same or linked repositories. In order to improve variant interpretation and avoid an exponential accumulation of confounding noise in the medical literature, the use of terms in a standard way should be sought and requested when reporting genetic variants and their consequences. Generally, stepwise and linear interpretation processes are likely to overrate some pieces of evidence while underscoring others. Algorithms are needed that allow a multidimensional, parallel analysis of diverse lines of evidence to be carried out by expert teams for specific genes, cellular pathways or disorders

Usefulness of cholestanol levels in the diagnosis and follow-up of patients with cerebrotendinous xanthomatosis

Introduction: Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disease caused by a deficiency of mitochondrial enzyme sterol 27-hydrolylase. Such a deficiency results in a reduced production of chenodeoxycholic acid and in an increased formation of cholestanol. It is clinically characterized by cataracts, diarrhoea, xanthomas, premature arteriosclerosis and a number of progressive neurological symptoms. Although cholestanol levels are used for the diagnosis of CTX, their correlation with the clinical symptoms and their prognostic usefulness have not been assessed so far. Methods: We reviewed 14 CTX patients diagnosed between 1995 and 2008 in two reference centres for the genetic diagnosis of this disorder, whose cholestanol levels had been recorded. We studied the main demographic, clinical and therapeutical data and their correlation with plasma cholestanol levels. Results: The average cholestanol level at diagnosis was 105.8 μmol/l. These levels did not correlate with any neurological symptoms or with disability at diagnosis scored by the EDSS. After treatment, all patients achieved a significant reduction in plasma cholestanol levels (average reduction of 91 μmol/l in an average follow-up of 34 months), although only one patient remained clinically stable. Conclusions: High cholestanol levels are very useful for diagnosis of CTX but they do not have a prognostic value (they do not correlate with severity). Normalization of cholestanol levels is not always associated with clinical stabilization. However, follow-up of cholestanol levels can be useful for the dose adjustment. Resumen: Introducción: La xantomatosis cerebro-tendinosa (XCT) es una enfermedad autosómica recesiva producida por un déficit del enzima 27-hidroxilasa. Como consecuencia, existe una deficiencia de ácido quenodeoxicólico y una sobreproducción de colestanol que se deposita en los tejidos. Clínicamente cursa con cataratas, diarrea, xantomas y diferentes síntomas neurológicos. A pesar de que los niveles de colestanol se emplean en el diagnóstico de la XCT, se desconoce su correlación con la clínica y el pronóstico. Métodos: Se han revisado 14 pacientes de XCT, diagnosticados entre 1995 y 2008 en dos centros de referencia para el diagnóstico genético, en los que se había determinado el colestanol. Se han estudiado los principales datos demográficos, clínicos y terapéuticos y su posible relación con los niveles de colestanol. Resultados: La media de los niveles de colestanol al diagnóstico fue de 106 μmol/l. No se encontró ninguna relación entre el colestanol plasmático y los diferentes síntomas neurológicos, ni con el grado de discapacidad al diagnóstico medido mediante la EDSS. Tras la instauración del tratamiento se obtuvo una reducción significativa del colestanol plasmático en todos los casos (reducción media de 91 μmol/l en una media de 34 meses), a pesar de lo cual sólo un paciente se estabilizó clínicamente. Conclusiones: La presencia de niveles elevados de colestanol es muy útil para el diagnóstico de la XCT, pero no tiene valor pronóstico (no se correlaciona con la situación funcional). Su normalización no siempre se acompaña de una estabilización clínica, pero su monitorización puede ser útil para el ajuste del tratamiento. Keywords: Cerebrotendinous xanthomatosis, Cholestanol, Chenodeoxycholic acid, Palabras clave: Xantomatosis cerebro-tendinosa, Colestanol, Ácido quenodeoxicólic

Utilidad de los niveles de colestanol en el diagnóstico y seguimiento de los pacientes con xantomatosis cerebrotendinosa

Resumen: Introducción: la xantomatosis cerebro-tendinosa (XCT) es una enfermedad autosómica recesiva producida por un déficit de la enzima 27-hidroxilasa. Como consecuencia, existe una deficiencia de ácido quenodeoxicólico y una sobreproducción de colestanol que se deposita en los tejidos. Clínicamente cursa con cataratas, diarrea, xantomas y diferentes síntomas neurológicos. A pesar de que los niveles de colestanol se emplean en el diagnóstico de la XCT, se desconoce su correlación con la clínica y el pronóstico. Métodos: se han revisado 14 pacientes afectos de XCT, diagnosticados entre 1995 y 2008 en dos centros de referencia para el diagnóstico genético, en los que se había determinado el colestanol. Se han estudiado los principales datos demográficos, clínicos y terapéuticos y su posible relación con los niveles de colestanol. Resultados: la media de los niveles de colestanol al diagnóstico fue de 106 μmol/ l. No se encontró ninguna relación entre el colestanol plasmático y los diferentes síntomas neurológicos, ni con el grado de discapacidad al diagnóstico medido mediante la EDSS. Tras la instauración del tratamiento se obtuvo una reducción significativa del colestanol plasmático en todos los casos (reducción media de 91 μmol/ l en una media de 34 meses), a pesar de lo cual sólo un paciente se estabilizó clínicamente. Conclusiones: la presencia de niveles elevados de colestanol es muy útil para el diagnóstico de la XCT, pero no tiene valor pronóstico (no se correlaciona con la situación funcional). Su normalización no siempre se acompaña de una estabilización clínica, pero su monitorización puede ser útil para el ajuste del tratamiento. Abstract: Introduction: cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disease caused by a deficiency of mitochondrial enzyme sterol 27-hydrolylase. Such a deficiency results in a reduced production of chenodeoxycholic acid and in an increased formation of cholestanol. It is clinically characterized by cataracts, diarrhoea, xanthomas, premature arteriosclerosis and a number of progressive neurological symptoms. Although cholestanol levels are used for the diagnosis of CTX, their correlation with the clinical symptoms and their prognostic usefulness have not been assessed so far. Methods: we reviewed 14 CTX patients diagnosed between 1995 and 2008 in two reference centres for the genetic diagnosis of this disorder, whose cholestanol levels had been recorded. We studied the main demographic, clinical and therapeutical data and their correlation with plasma cholestanol levels. Results: the average cholestanol level at diagnosis was 105.8 μmol/l. These levels did not correlate with any neurological symptoms or with disability at diagnosis scored by the EDSS. After treatment, all patients achieved a significant reduction in plasma cholestanol levels (average reduction of 91 μmol/l in an average follow-up of 34 months), although only one patient remained clinically stable. Conclusions: high cholestanol levels are very useful for diagnosis of CTX but they do not have a prognostic value (they do not correlate with severity). Normalisation of cholestanol levels is not always associated with clinical stabilisation. However, follow-up of cholestanol levels can be useful for the dose adjustment. Palabras clave: Xantomatosis cerebro-tendinosa, Colestanol, Ácido quenodeoxicólico, Keywords: Cerebrotendinous xanthomatosis, Cholestanol, Chenodeoxycholic aci