Boczek, Nicole J.

Background: The dynamin 1-like gene ( DNM1L) encodes a GTPase that mediates mitochondrial and peroxisomal fission and fusion. We report a new clinical presentation associated with a DNM1L pathogenic variant and review the literature. Results: A 13-year-old boy with mild developmental delays and paroxysmal dystonia presented acutely with multifocal myoclonic super-refractory status epilepticus. Despite sustained and aggressive treatment, seizures persisted and care was ultimately withdrawn in the context of extensive global cortical atrophy. Rapid trio-whole exome sequencing revealed a de novo heterozygous c.1207C>T (p.R403C) pathogenic variant in DNM1L. Immunofluorescence staining of fibroblast mitochondria revealed abnormally elongated and tubular morphology. Conclusions: This case highlights the diagnostic importance of rapid whole exome sequencing within a critical care setting and reveals the expanding phenotypic spectrum associated with DNM1L variants. This now includes progressive paroxysmal dystonia and adolescent-onset super-refractory myoclonic status epilepticus contributing to strikingly rapid and progressive cortical atrophy and death.

Abstract Background Pathogenic variants in ryanodine receptor 1 ( RYR 1, MIM # 180901) are the cause of congenital myopathy with fiber‐type disproportion, malignant hyperthermia susceptibility type 1, central core disease of muscle, multiminicore disease and other congenital myopathies. Methods We present a patient with global developmental delay, hypotonia, myopathy, joint hypermobility, and multiple other systemic complaints that were noted early in life. Later she was found to have multiple bone deformities involving her spine, with severe scoliosis that was corrected surgically. She was also diagnosed with ophthalmoplegia, chronic hypercapnic respiratory failure, and hypertension. At 22 years of age she presented to the genetics clinic with a diagnosis of mitochondrial myopathy and underwent whole exome sequencing ( WES ). Results Whole exome sequencing revealed two novel compound heterozygous variants in RYR 1 (c.7060_7062del, p.Val2354del and c.4485_4500del, p.Tyr1495X). Conclusion Review of her clinical, pathologic, and genetic findings pointed to a diagnosis of a congenital myopathy with fiber‐type disproportion.

STAR syndrome is a rare X‐linked dominant disorder characterized by toe Syndactyly, Telecanthus, Anogenital malformations, and Renal malformations, and is caused by loss‐of‐function variants in FAM58A. Our proband presented with the hallmark features of STAR syndrome, as well as some additional less typical features including tethered cord and hearing loss. The proband's mother and maternal half‐sister had similar clinical histories, but had variability in phenotypic severity. Clinical whole exome sequencing revealed a novel pathogenic nonsense variant, c.651G>A (p.Trp217X; NM_152274), in FAM58A in the proband, mother, and maternal half‐sister. This pedigree represents the 11–13th patients described with STAR syndrome and the third instance of familial inheritance. To our knowledge, this is the first occurrence of a nonsense variant in FAM58A described in individuals with STAR syndrome and the phenotype in this pedigree suggests that tethered cord and hearing loss are features of STAR syndrome.

AbstractBackgroundWe characterized the pharmacogenomics (PGx) results received by diagnostic odyssey patients as secondary findings during clinical whole exome sequencing (WES) testing as a part of their care in Mayo Clinic's Individualized Medicine Clinic to determine the potential benefits and limitations to this cohort.MethodsWES results on 94 patients included a subset of PGx variants in CYP2C19, CYP2C9, and VKORC1 if identified in the patient. Demographic, phenotypic, and medication usage information was abstracted from patient medical data. A pharmacist interpreted the PGx results in the context of the patients’ current medication use and made therapeutic recommendations.ResultsThe majority was young with a median age of 10 years old, had neurological involvement in the disease presentation (71%), and was currently taking medications (90%). Of the 94 PGx‐evaluated patients, 91% had at least one variant allele reported and 20% had potential immediate implications on current medication use.ConclusionDue to the disease complexity and medication needs of diagnostic odyssey patients, there may be immediate benefit obtained from early life PGx testing for many and most will likely find benefit in the future. These results require conscientious interpretation and management to be actionable for all prescribing physicians throughout the lifetime of the patient.

AbstractBackgroundKleefstra Syndrome (KS) (MIM# 610253) is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase‐1 (EHMT1, GLP). EHMT1 (MIM# 607001) encodes a histone methyltransferase that heterodimerizes with EHMT2 (also known as G9a, MIM# 604599), which together are responsible for mono‐ and dimethylation of H3 lysine 9 (H3K9me1 and ‐me2), resulting in transcriptional repression of target genes.MethodsThis report describes an 18‐year‐old woman with intellectual disability, severely limited speech, hypotonia, microcephaly, and facial dysmorphisms, who was found to have a novel de novo single‐base frameshift deletion in EHMT1.ResultsFunctional studies using patient fibroblasts showed decreased H3K9me2 compared to wild‐type control cells, thus providing a rapid confirmatory test that complements molecular studies.ConclusionWhole exome sequencing revealed a novel frameshift deletion in EHMT1 after a lengthy diagnostic odyssey in this patient. Functional testing using this patient's fibroblasts provides proof‐of‐concept for the analysis of variants of uncertain significance that are predicted to impact EHMT1 enzymatic activity.

Loeys-Dietz syndrome (LDS) is a connective tissue disorder characterized by vascular findings of aneurysm and/or dissection of cerebral, thoracic, or abdominal arteries and skeletal findings. We report a case of a novel pathogenic variant in TGFBR2 and phenotype consistent with classic LDS. The proband was a 10-year-old presenting to the genetics clinic with an enlarged aortic root (Z-scores 5-6), pectus excavatum, and congenital contractures of the right 2nd and 3rd digit. Molecular testing of TGFBR2 was sent to a commercial laboratory and demonstrated a novel, likely pathogenic, variant in exon 4, c.1061T>C, p.(L354P). Molecular modeling reveals alteration of local protein structure as a result of this pathogenic variant. This pathogenic variant has not been previously reported in LDS and thus expands the pathogenic variant spectrum of this condition.

Key Clinical MessageA de novo GFAP variant, p.R376W, was identified in a child presenting with hypotonia, developmental delay, and abnormal brain MRI. Following the 2015 ACMG variant classification guidelines and the functional studies showing protein aggregate formation in vitro, p.R376W should be classified as a pathogenic variant, causative for Alexander disease.

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