RESUMEN
The National Institutes of Health Undiagnosed Diseases Program evaluates patients for whom no diagnosis has been discovered despite a comprehensive diagnostic workup. Failure to diagnose a condition may arise from the mutation of genes previously unassociated with disease. However, we hypothesized that this could also co-occur with multiple genetic disorders. Demonstrating a complex syndrome caused by multiple disorders, we report two siblings manifesting both similar and disparate signs and symptoms. They shared a history of episodes of hypoglycemia and lactic acidosis, but had differing exam findings and developmental courses. Clinical acumen and exome sequencing combined with biochemical and functional studies identified three genetic conditions. One sibling had Smith-Magenis Syndrome and a nonsense mutation in the RAI1 gene. The second sibling had a de novo mutation in GRIN2B, which resulted in markedly reduced glutamate potency of the encoded receptor. Both siblings had a protein-destabilizing homozygous mutation in PCK1, which encodes the cytosolic isoform of phosphoenolpyruvate carboxykinase (PEPCK-C). In summary, we present the first clinically-characterized mutation of PCK1 and demonstrate that complex medical disorders can represent the co-occurrence of multiple diseases.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/genética , Fosfoenolpiruvato Carboxiquinasa (ATP)/deficiencia , Fosfoenolpiruvato Carboxiquinasa (GTP)/genética , Receptores de N-Metil-D-Aspartato/genética , Síndrome de Smith-Magenis/diagnóstico , Factores de Transcripción/genética , Secuencia de Aminoácidos , Secuencia de Bases , Niño , Preescolar , Análisis Mutacional de ADN , Femenino , Estudios de Asociación Genética , Células HEK293 , Humanos , Datos de Secuencia Molecular , Mutación Missense , Polimorfismo de Nucleótido Simple , Síndrome de Smith-Magenis/genética , TransactivadoresRESUMEN
Early-onset myopathy, areflexia, respiratory distress and dysphagia (EMARDD) is a myopathic disorder associated with mutations in MEGF10. By novel analysis of SNP array hybridization and exome sequence coverage, we diagnosed a 10-years old girl with EMARDD following identification of a novel homozygous deletion of exon 7 in MEGF10. In contrast to previously reported EMARDD patients, her weakness was more prominent proximally than distally, and involved her legs more than her arms. MRI of her pelvis and thighs showed muscle atrophy and fatty replacement. Ultrasound of several muscle groups revealed dense homogenous increases in echogenicity. Cloning and sequencing of the deletion breakpoint identified features suggesting the mutation arose by fork stalling and template switching. These findings constitute the first genomic deletion causing EMARDD, expand the clinical phenotype, and provide new insight into the pattern and histology of its muscular pathology.
Asunto(s)
Trastornos de Deglución/genética , Exones/genética , Proteínas de la Membrana/genética , Enfermedades Musculares/genética , Mutación/genética , Trastornos Respiratorios/genética , Eliminación de Secuencia , Niño , Mapeo Cromosómico , Trastornos de Deglución/diagnóstico , Femenino , Homocigoto , Humanos , Enfermedades Musculares/diagnóstico , Linaje , Fenotipo , Polimorfismo de Nucleótido Simple/genéticaRESUMEN
PURPOSE: This report describes the National Institutes of Health Undiagnosed Diseases Program, details the Program's application of genomic technology to establish diagnoses, and details the Program's success rate during its first 2 years. METHODS: Each accepted study participant was extensively phenotyped. A subset of participants and selected family members (29 patients and 78 unaffected family members) was subjected to an integrated set of genomic analyses including high-density single-nucleotide polymorphism arrays and whole exome or genome analysis. RESULTS: Of 1,191 medical records reviewed, 326 patients were accepted and 160 were admitted directly to the National Institutes of Health Clinical Center on the Undiagnosed Diseases Program service. Of those, 47% were children, 55% were females, and 53% had neurologic disorders. Diagnoses were reached on 39 participants (24%) on clinical, biochemical, pathologic, or molecular grounds; 21 diagnoses involved rare or ultra-rare diseases. Three disorders were diagnosed based on single-nucleotide polymorphism array analysis and three others using whole exome sequencing and filtering of variants. Two new disorders were discovered. Analysis of the single-nucleotide polymorphism array study cohort revealed that large stretches of homozygosity were more common in affected participants relative to controls. CONCLUSION: The National Institutes of Health Undiagnosed Diseases Program addresses an unmet need, i.e., the diagnosis of patients with complex, multisystem disorders. It may serve as a model for the clinical application of emerging genomic technologies and is providing insights into the characteristics of diseases that remain undiagnosed after extensive clinical workup.
