Two Cockayne Syndrome patients with a novel splice site mutation - clinical and metabolic analyses.

Cockayne Syndrome (CS) is a rare autosomal recessive disorder, which leads to neurodegeneration, growth failure and premature aging. Most of the cases are due to mutations in the ERCC6 gene, which encodes the protein CSB. CSB is involved in several functions including DNA repair and transcription. Here we describe two Danish brothers with CS. Both patients carried a novel splice site mutation (c.2382+2T>G), and a previously described nonsense mutation (c.3259C>T, p.Arg1087X) in a biallelic state. Both patients presented the cardinal features of the disease including microcephaly, congenital cataract and postnatal growth failure. In addition, their fibroblasts were hypersensitive to UV irradiation and exhibited increased superoxide levels in comparison to fibroblasts from healthy age and gender matched individuals. Metabolomic analysis revealed a distinctive metabolic profile in cells from the CS patients compared to control cells. Among others, α-ketoglutarate, hydroxyglutarate and certain amino acids (ornithine, proline and glycine) were reduced in the CS patient fibroblasts, whereas glycolytic intermediates (glucose-6-phosphate and pyruvic acid) and fatty acids (palmitic, stearic and myristic acid) were increased. Our data not only provide additional information to the database of CS mutations, but also point towards targets for potential treatment of this devastating disease.

Hyperammonemia as a Presenting Feature in Two Siblings with FBXL4 Variants.

Early-onset mitochondrial encephalomyopathy is a rare disorder that presents in the neonatal period with lactic acidosis, hypotonia, and developmental delay. Sequence variants in the nuclear-encoded gene FBXL4 have been previously demonstrated to be a cause of early-onset mitochondrial encephalomyopathy in several unrelated families. We have identified a pair of siblings with mutations in FBXL4 who each presented in the neonatal period with hyperammonemia, low plasma levels of aspartate, low urine levels of tricarboxylic acid cycle intermediates suggesting a defect in anaplerosis, and cerebellar hypoplasia in addition to lactic acidosis and other classic signs of mitochondrial encephalomyopathy. After initial clinical stabilization, both subjects continued to have episodic exacerbations characterized by lactic acidosis and hyperammonemia. Previously reported cases of FBXL4 mutations are reviewed and compared with these affected siblings. These two new cases add to the spectrum of disease caused by mutations in FBLX4 and suggest possible benefit from anaplerotic therapies.

A Phase 3 Trial of Sebelipase Alfa in Lysosomal Acid Lipase Deficiency.

BACKGROUND: Lysosomal acid lipase is an essential lipid-metabolizing enzyme that breaks down endocytosed lipid particles and regulates lipid metabolism. We conducted a phase 3 trial of enzyme-replacement therapy in children and adults with lysosomal acid lipase deficiency, an underappreciated cause of cirrhosis and severe dyslipidemia. METHODS: In this multicenter, randomized, double-blind, placebo-controlled study involving 66 patients, we evaluated the safety and effectiveness of enzyme-replacement therapy with sebelipase alfa (administered intravenously at a dose of 1 mg per kilogram of body weight every other week); the placebo-controlled phase of the study was 20 weeks long and was followed by open-label treatment for all patients. The primary end point was normalization of the alanine aminotransferase level. Secondary end points included additional disease-related efficacy assessments, safety, and side-effect profile. RESULTS: Substantial disease burden at baseline included a very high level of low-density lipoprotein cholesterol (≥190 mg per deciliter) in 38 of 66 patients (58%) and cirrhosis in 10 of 32 patients (31%) who underwent biopsy. A total of 65 of the 66 patients who underwent randomization completed the double-blind portion of the trial and continued with open-label treatment. At 20 weeks, the alanine aminotransferase level was normal in 11 of 36 patients (31%) in the sebelipase alfa group and in 2 of 30 (7%) in the placebo group (P=0.03), with mean changes from baseline of -58 U per liter versus -7 U per liter (P<0.001). With respect to prespecified key secondary efficacy end points, we observed improvements in lipid levels and reduction in hepatic fat content (P<0.001 for all comparisons, except P=0.04 for triglycerides). The number of patients with adverse events was similar in the two groups; most events were mild and were considered by the investigator to be unrelated to treatment. CONCLUSIONS: Sebelipase alfa therapy resulted in a reduction in multiple disease-related hepatic and lipid abnormalities in children and adults with lysosomal acid lipase deficiency. (Funded by Synageva BioPharma and others; ARISE ClinicalTrials.gov number, NCT01757184.).

Management of a Woman With Maple Syrup Urine Disease During Pregnancy, Delivery, and Lactation.

Maple syrup urine disease (MSUD) is an inherited disorder of metabolism of the branched-chain amino acids leucine, isoleucine, and valine. Complications of acute elevation in plasma leucine include ketoacidosis and risk of cerebral edema, which can be fatal. Individuals with MSUD are at risk of metabolic crisis throughout life, especially at times of physiological stress. We present a case of successful management of a woman with MSUD through pregnancy, delivery, postpartum, and lactation, including nutrition therapy using modified parenteral nutrition.

Homozygous PLCB1 deletion associated with malignant migrating partial seizures in infancy.

Malignant migrating partial seizures in infancy (MMPEI) is an early onset epileptic encephalopathy with few known etiologies. We sought to identify a novel cause of MMPEI in a child with MMPEI whose healthy parents were consanguineous. We used array comparative genomic hybridization (CGH) to identify copy number variants genome-wide and long-range polymerase chain reaction to further delineate the breakpoints of a deletion found by CGH. The proband had an inherited homozygous deletion of chromosome 20p13, disrupting the promoter region and first three coding exons of the gene PLCB1. Additional MMPEI cases were screened for similar deletions or mutations in PLCB1 but did not harbor mutations. Our results suggest that loss of PLCß1 function is one cause of MMPEI, consistent with prior studies in a Plcb1 knockout mouse model that develops early onset epilepsy. We provide novel insight into the molecular mechanisms underlying MMPEI and further implicate PLCB1 as a candidate gene for severe childhood epilepsies. This work highlights the importance of pursuing genetic etiologies for severe early onset epilepsy syndromes.

Mutations in UVSSA cause UV-sensitive syndrome and destabilize ERCC6 in transcription-coupled DNA repair.

UV-sensitive syndrome (UV(S)S) is an autosomal recessive disorder characterized by photosensitivity and deficiency in transcription-coupled repair (TCR), a subpathway of nucleotide-excision repair that rapidly removes transcription-blocking DNA damage. Cockayne syndrome is a related disorder with defective TCR and consists of two complementation groups, Cockayne syndrome (CS)-A and CS-B, which are caused by mutations in ERCC8 (CSA) and ERCC6 (CSB), respectively. UV(S)S comprises three groups, UV(S)S/CS-A, UV(S)S/CS-B and UV(S)S-A, caused by mutations in ERCC8, ERCC6 and an unidentified gene, respectively. Here, we report the cloning of the gene mutated in UV(S)S-A by microcell-mediated chromosome transfer. The predicted human gene UVSSA (formerly known as KIAA1530)(7) corrects defective TCR in UV(S)S-A cells. We identify three nonsense and frameshift UVSSA mutations in individuals with UV(S)S-A, indicating that UVSSA is the causative gene for this syndrome. The UVSSA protein forms a complex with USP7 (ref. 8), stabilizes ERCC6 and restores the hypophosphorylated form of RNA polymerase II after UV irradiation.

Response of motor complications in Cockayne syndrome to carbidopa-levodopa.

BACKGROUND: Gait difficulties, tremors, and coordination difficulties are common features of Cockayne syndrome that are consequences of leukodystrophy, cerebellar atrophy, and demyelinating neuropathy, but no pharmacotherapy for these disabling symptoms is available. OBJECTIVE: To determine whether carbidopa-levodopa relieves tremors and other motor complications of Cockayne syndrome. DESIGN: Mutation analysis and case report study. SETTING: Hospital clinic and genetics research laboratory. Patients We studied 3 patients with Cockayne syndrome, a rare autosomal recessive neurodegenerative disorder for which no known treatments are available. Intervention Carbidopa-levodopa therapy. MAIN OUTCOME MEASURES: Status of tremors, ability to perform daily tasks, serial physical examinations, and results of handwriting samples. RESULTS: All 3 patients had a clear reduction in tremors and improvements in handwriting and manipulation of utensils and cups. CONCLUSIONS: Patients with Cockayne syndrome should be evaluated carefully for movement disorders. A clinical trial should be considered to evaluate this therapy further.

Clinical studies in familial VCP myopathy associated with Paget disease of bone and frontotemporal dementia.

Inclusion body myopathy with Paget disease of the bone (PDB) and/or frontotemporal dementia (IBMPFD, OMIM 167320), is a progressive autosomal dominant disorder caused by mutations in the Valousin-containing protein (VCP, p97 or CDC48) gene. IBMPFD can be difficult to diagnose. We assembled data on a large set of families to illustrate the number and type of misdiagnoses that occurred. Clinical analysis of 49 affected individuals in nine families indicated that 42 (87%) of individuals had muscle disease. The majority were erroneously diagnosed with limb girdle muscular dystrophy (LGMD), facioscapular muscular dystrophy, peroneal muscular dystrophy, late adult onset distal myopathy, spinal muscular atrophy, scapuloperoneal muscular dystrophy, or amyotrophic lateral sclerosis (ALS) among others. Muscle biopsies showed rimmed vacuoles characteristic of an inclusion body myopathy in 7 of 18 patients (39%), however, inclusion body myopathy was correctly diagnosed among individuals in only families 5 and 15. Frontotemporal dementia (FTD) was diagnosed in 13 individuals (27%) at a mean age of 57 years (range 48.9-60.2 years); however, several individuals had been diagnosed with Alzheimer disease. Histopathological examination of brains of three affected individuals revealed a pattern of ubiquitin positive neuronal intranuclear inclusions and dystrophic neurites. These families expand the clinical phenotype in IBMPFD, a complex disorder caused by mutations in VCP. The presence of PDB in 28 (57%) individuals suggests that measuring serum alkaline phosphatase (ALP) activity may be a useful screen for IBMPFD in patients with myopathy.