LPIN1-related myolysis constitutes a major cause of early-onset rhabdomyolysis and occasionally in adults. Heterozygous LPIN1 mutations may cause mild muscular symptoms. No major defects of LPIN2 or LPIN3 genes were associated with muscular manifestations.

Transcobalamin (TC) transports cobalamin from blood into cells. TC deficiency is a rare autosomal recessive disorder usually presenting in early infancy with failure to thrive, weakness, diarrhoea, pallor, anemia, and pancytopenia or agammaglobulinemia. It can sometimes resemble neonatal leukemia or severe combined immunodeficiency disease. Diagnosis of TC deficiency is suspected based on megaloblastic anemia, elevation of total plasma homocysteine, and blood or urine methylmalonic acid. It is confirmed by studying the synthesis of TC in cultured fibroblasts, or by molecular analysis of the TCN2 gene. TC deficiency is treatable with supplemental cobalamin, but the optimal type, route and frequency of cobalamin administration and long term patient outcomes are unknown. Here we present a series of 30 patients with TC deficiency, including an update on multiple previously published patients, in order to evaluate the different treatment strategies and provide information about long term outcome. Based on the data presented, current practice appears to favour treatment of individuals with TC deficiency by intramuscular injections of hydroxy- or cyanocobalamin. In most cases presented, at least weekly injections (1 mg IM) were necessary to ensure optimal treatment. Most centres adjusted the treatment regimen based on monitoring CBC, total plasma homocysteine, plasma and urine methylmalonic acid, as well as, clinical status. Finally, continuing IM treatment into adulthood appears to be beneficial.

Pontocerebellar hypoplasia type 6 (PCH6) (MIM #611523) is a recently described disorder caused by mutations in RARS2 (MIM *611524), the gene encoding mitochondrial arginyl-transfer RNA (tRNA) synthetase, a protein essential for translation of all mitochondrially synthesised proteins. This case confirms that progressive cerebellar and cerebral atrophy with microcephaly and complex epilepsy are characteristic features of PCH6. Additional features of PCH subtypes 2 and 4, including severe dystonia, optic atrophy and thinning of the corpus callosum, are demonstrated. Congenital lactic acidosis can be present, but respiratory chain dysfunction may be mild or absent, suggesting that disordered mitochondrial messenger RNA (mRNA) translation may not be the only mechanism of impairment or that a secondary mechanism exists to allow some translation. We report two novel mutations and expand the phenotypic spectrum of this likely underdiagnosed PCH variant, where recognition of the characteristic neuroradiological phenotype could potentially expedite genetic diagnosis and limit invasive investigations.

A wide spectrum of IEM are followed at adult centres. Specific knowledge of these disorders is needed to provide optimal care including up-to-date knowledge of treatments and ability to manage acute decompensation.

ObjectiveTo expand the phenotypic spectrum of severity of POLR3-related leukodystrophy and identify genotype-phenotype correlations through study of patients with extremely severe phenotypes.MethodsWe performed an international cross-sectional study on patients with genetically proven POLR3-related leukodystrophy and atypical phenotypes to identify 6 children, 3 males and 3 females, with an extremely severe phenotype compared with that typically reported. Clinical, radiologic, and molecular features were evaluated for all patients, and functional and neuropathologic studies were performed on 1 patient.ResultsEach patient presented between 1 and 3 months of age with failure to thrive, severe dysphagia, and developmental delay. Four of the 6 children died before age 3 years. MRI of all patients revealed a novel pattern with atypical characteristics, including progressive basal ganglia and thalami abnormalities. Neuropathologic studies revealed patchy areas of decreased myelin in the cerebral hemispheres, cerebellum, brainstem, and spinal cord, with astrocytic gliosis in the white matter and microglial activation. Cellular vacuolization was observed in the thalamus and basal ganglia, and neuronal loss was evident in the putamen and caudate. Genotypic similarities were also present between all 6 patients, with one allele containing a POLR3A variant causing a premature stop codon and the other containing a specific intronic splicing variant (c.1771-7C>G), which produces 2 aberrant transcripts along with some wild-type transcript.ConclusionsWe describe genotype-phenotype correlations at the extreme end of severity of the POLR3-related leukodystrophy spectrum and shed light on the complex disease pathophysiology.

Two male siblings from a consanguineous union presented in early infancy with marked truncal hypotonia, a general paucity of movement, extrapyramidal signs and cognitive delay. By mid-childhood they had made little developmental progress and remained severely hypotonic and bradykinetic. They developed epilepsy and had problems with autonomic dysfunction and oculogyric crises. They had a number of orthopaedic problems secondary to their hypotonia. Cerebrospinal fluid (CSF) neurotransmitters were initially normal, apart from mildly elevated 5-hydroxyindolacetic acid, and the children did not respond favourably to a trial of levodopa-carbidopa. The youngest died from respiratory complications at 10 years of age. Repeat CSF neurotransmitters in the older sibling at eight years of age showed slightly low homovanillic acid and 5-hydroxyindoleacetic acid levels. Whole-exome sequencing revealed a novel mutation homozygous in both children in the monoamine transporter gene SLC18A2 (p.Pro237His), resulting in brain dopamine-serotonin vesicular transport disease. This is the second family to be described with a mutation in this gene. Treatment with the dopamine agonist pramipexole in the surviving child resulted in mild improvements in alertness, communication, and eye movements. This case supports the identification of the causal mutation in the original case, expands the clinical phenotype of brain dopamine-serotonin vesicular transport disease and confirms that pramipexole treatment may lead to symptomatic improvement in affected individuals.

When screening for carnitine uptake disorder (CUD), the New Zealand (NZ) newborn screening (NBS) service identified infants as screen-positive if they had initial and repeat free carnitine (C0) levels of less than 5.0 μmol/L. Since 2006, the NBS service has identified two infants with biochemical and genetic features consistent with neonatal CUD and nine mothers with features consistent with maternal CUD. A review of the literature suggests that these nine women reflect less than half the true prevalence and that CUD is relatively common. However, the NZ results (two infants) suggest a very low sensitivity and positive predictive value of NBS.While patients presenting with significant disease due to CUD are well described, the majority of adults with CUD are asymptomatic. Nonetheless, treatment with highdose oral L-carnitine is recommended. Compliance with oral L-carnitine is likely to be poor long term. This may represent a specific risk as treatment could repress the usual compensatory mechanisms seen in CUD, such that a sudden discontinuation of treatment may be dangerous. L-carnitine is metabolized to trimethylamine-N-oxide (TMAO) and treated patients have extremely high plasma TMAO levels. TMAO is an independent risk factor for atherosclerosis and, thus, caution should be exercised regarding long-term treatment with high-dose carnitine of asymptomatic patients who may have a biochemical profile without disease. Due to these concerns, the NZ Newborn Metabolic Screening Programme (NMSP) initiated a review via a series of advisory and governance committees and decided to discontinue screening for CUD.

The current treatment of mucopolysaccharidosis type II (MPS II, Hunter syndrome) is enzyme replacement therapy with recombinant idursulfase (Elaprase®). The efficacy of ERT was established based primarily on reduction in urine glycosaminoglycans:creatinine (GAG:Cr) ratio and improvement in a composite score of predicted forced vital capacity (FVC% predicted) and 6-min walk-test distance (6MWT). We retrospectively reviewed these parameters in 11 boys with MPS II treated with idursulfase between April 2007 (or the time of diagnosis) and February 2010. Some results were inconsistent with published trial data, and there was only a small number of analyzable results obtained for the FVC% predicted and 6MWT. A major drawback was the high prevalence of neurological involvement and young age of patients in the study cohort compared with the clinical trials. This study emphasizes the limitations of the current tools utilized to monitor ERT efficacy and MPS II disease burden in clinical practice.