De novo pathogenic DNM1L variant in a patient diagnosed with atypical hereditary sensory and autonomic neuropathy.

BACKGROUND: Profiling the entire genome at base pair resolution in a single test offers novel insights into disease by means of dissection of genetic contributors to phenotypic features. METHODS: We performed genome sequencing for a patient who presented with atypical hereditary sensory and autonomic neuropathy, severe epileptic encephalopathy, global developmental delay, and growth hormone deficiency. RESULTS: Assessment of the variants detected by mapped sequencing reads followed by Sanger confirmation revealed that the proband is a compound heterozygote for rare variants within RETREG1 (FAM134B), a gene associated with a recessive form of hereditary sensory and autonomic neuropathy, but not with epileptic encephalopathy or global developmental delay. Further analysis of the data also revealed a heterozygous missense variant in DNM1L, a gene previously implicated in an autosomal dominant encephalopathy, epilepsy, and global developmental delay and confirmed by Sanger sequencing to be a de novo variant not present in parental genomes. CONCLUSIONS: Our findings emphasize the importance of genome-wide sequencing in patients with a well-characterized genetic disease with atypical presentation. This approach reduces the potential for misdiagnoses.

Pyruvate Carboxylase Deficiency Type C: A Rare Cause of Acute Transient Flaccid Paralysis with Ketoacidosis.

Pyruvate carboxylase (PC) is a biotin-containing enzyme that is responsible for the adenosine triphosphate-dependent carboxylation of pyruvate to oxaloacetate, a key intermediate in the tricarboxylic acid cycle. PC deficiency (OMIM 266150) is a rare autosomal recessive metabolic disease, causing elevation of pyruvate, lactate, and alanine. Three types of PC deficiency have been described in the literature; A, B, and C. Type A PC deficiency, also called infantile or North American type, is characterized by infantile onset acidosis, failure to thrive, and developmental delay. The second subtype or type B, the neonatal or French form, presents usually in the neonatal period, mostly in the first 72 hours of life with severe lactic acidosis, truncal hypotonia, and seizures. The third type is called type C, is extremely rare with few cases published in the literature. In this case report, we present an 11-month-old girl who presented with acute flaccid paralysis, lethargy, and constipation with elevated ketones and lactate. She was confirmed genetically and biochemically to have PC deficiency type C. The patient's unusual presentation expands the clinical phenotype of this extremely rare disease.

De novo mutations in the SET nuclear proto-oncogene, encoding a component of the inhibitor of histone acetyltransferases (INHAT) complex in patients with nonsyndromic intellectual disability.

The role of disturbed chromatin remodeling in the pathogenesis of intellectual disability (ID) is well established and illustrated by de novo mutations found in a plethora of genes encoding for proteins of the epigenetic regulatory machinery. We describe mutations in the "SET nuclear proto-oncogene" (SET), encoding a component of the "inhibitor of histone acetyltransferases" (INHAT) complex, involved in transcriptional silencing. Using whole exome sequencing, four patients were identified with de novo mutations in the SET gene. Additionally, an affected mother and child were detected who carried a frameshift variant in SET. Four patients were found in literature. The de novo mutations in patients affected all four known SET mRNA transcripts. LoF mutations in SET are exceedingly rare in the normal population and, if present, affect only one transcript. The pivotal role of SET in neurogenesis is evident from in vitro and animal models. SET interacts with numerous proteins involved in histone modification, including proteins encoded by known autosomal dominant ID genes, that is, EP300, CREBBP, SETBP1, KMT2A, RAC1, and CTCF. Our study identifies SET as a new component of epigenetic regulatory modules underlying human cognitive disorders, and as a first member of the Nucleosome Assembly Protein (NAP) family implicated in ID.

Eye Findings on Vigabatrin and Taurine Treatment in Two Patients with Succinic Semialdehyde Dehydrogenase Deficiency.

We describe for the first time two patients with succinic semialdehyde dehydrogenase (SSADH) deficiency, who were found to have abnormal electroretinogram (ERG) examinations at baseline, or 6 months after vigabatrin treatment was started. This was somewhat reversible with L-taurine treatment, or minimally progressive. The mechanism of injury to the retina may be induced by elevations of γ-aminobutyric acid causing peripheral photoreceptor and ganglion cell damage, and this can be exacerbated by the use of vigabatrin. The use of taurine supplementation in tandem with vigabatrin may allow reversal of retinopathy and mitigate or slow down further deterioration. Further prospective clinical trials are required to evaluate this further. We recommend starting L-taurine therapy together with vigabatrin if a trial of vigabatrin is commenced in a patient with SSADH deficiency. Close monitoring of visual fields or ERG is also recommended at baseline and during vigabatrin therapy.

Hemiplegic migraine, seizures, progressive spastic paraparesis, mood disorder, and coma in siblings with low systemic serotonin.

BACKGROUND: Serotonin has an important role in vascular resistance and blood pressure control, and a functional serotonin transporter polymorphism has been associated with migraine. Disturbances in serotonin metabolism have been associated with autism, depression, and myoclonus related conditions, but serotonin has far more functions in the body. Familial hemiplegic migraine is a rare autosomal dominant subtype of migraine with aura in which attacks are associated with hemiparesis. CASES: We present two siblings with hemiplegic migraine, depression, progressive spastic paraparesis, myelopathy, and spinal cord atrophy. One of the sisters presented with prolonged coma after a migraine episode. Both sisters were found to have low cerebrospinal fluid serotonin metabolite (5-hydroxyindoleacetic acid), low platelet serotonin levels, and diminished serotonin transport capacity. Their clinical symptoms improved on 5-hydroxytryptophan replacement therapy. Mutational analysis of the CACNA1A and ATP1A2 genes was negative. CONCLUSION: This is the first time that systemic serotonin deficiency has been described in familial hemiplegic migraine. We hypothesize that the deficiency of serotonin transport may be part of a complex cellular membrane trafficking dysfunction involving not only the serotonin transporter but also other transporters and ion channels.

Newborn screening for MCAD deficiency: experience of the first three years in British Columbia, Canada.

BACKGROUND: Medium Chain Acyl-CoA Dehydrogenase (MCAD) Deficiency is an autosomal recessive disorder of fatty acid oxidation, with potential fatal outcome. MCAD deficiency is diagnosed by acylcarnitine analysis on newborn screening blood spot cards by tandem mass spectrometry. Early diagnosis of MCAD and presymptomatic treatment can potentially reduce morbidity and mortality. OBJECTIVES: To evaluate incidence, clinical outcome, biochemical and molecular phenotype of MCAD cases detected in the first three years of newborn screening in British Columbia (BC). METHODS AND RESULTS: Medium chain length acylcarnitines, octanoylcarnitine (C8) and decanoylcarnitine (C10), were measured on newborn screening blood spot cards. Out of 121,000 live births, 17 newborns had C8 values above the screening cut-off of 0.38 umol/L. Ten newborns had elevated C8 on repeat cards and were investigated further. Both C8 and C8/C10 ratios remained abnormal in all confirmed MCAD cases. Positive predictive value of screening was 58% with no false negative results. Seven patients were homozygous for the common c.985A > G MCAD mutation and three others were compound heterozygous for the c.985A > G and a second mutation. Two novel mutations were identified (c.260T > C and c.382T > A). The estimated incidence of MCAD was approximately 1:12,000 live births. Upon frequent feeding and carnitine supplementation, none of the patients had metabolic crises or adverse outcomes. CONCLUSION: Frequency of MCAD in BC is comparable to reports from other newborn screening programs. Persistence of elevated C8 levels and C8/C10 ratios in confirmed MCAD cases suggest that these are sensitive markers for newborn screening. Early detection and treatment have successfully prevented adverse health outcomes in patients with MCAD.

Autosomal recessive GTP cyclohydrolase I deficiency without hyperphenylalaninemia: evidence of a phenotypic continuum between dominant and recessive forms.

We describe a unique presentation of autosomal recessive (AR) GTP cyclohydrolase I (GTPCH) deficiency, with severe CNS involvement but without hyperphenylalaninemia. A male infant presented with progressive spasticity, dystonia and oculogyric episodes. Blood phenylalanine levels were persistently normal: whereas an oral phenylalanine loading test revealed impaired phenylalanine clearance. CSF neopterin and tetrahydrobiopterin (BH(4)) were low, homovanillic acid marginally low and 5-hydroxyindoleacetic acid normal. Fibroblasts showed decreased GTPCH enzyme activity. A homozygous novel mutation of GCH1, p.V206A, was identified. On treatment (BH(4), L-Dopa/Carbidopa and 5-hydroxytryptophan), motor development improved. Mutational analysis provided neonatal diagnosis of a younger brother who, after 18 months on treatment, shows normal development. AR GTPCH I deficiency can present without hyperphenylalaninemia and with normal or subtle CSF neurotransmitter profiles. Testing for GTPCH deficiency should be considered for patients with unexplained neurological symptoms and extrapyramidal movement disorder.