Julian Raiman

Mutations in DARS Cause Hypomyelination with Brain Stem and Spinal Cord Involvement and Leg Spasticity

Inherited white-matter disorders are a broad class of diseases for which treatment and classification are both challenging. Indeed, nearly half of the children presenting with a leukoencephalopathy remain without a specific diagnosis. Here, we report on the application of high-throughput genome and exome sequencing to a cohort of ten individuals with a leukoencephalopathy of unknown etiology and clinically characterized by hypomyelination with brain stem and spinal cord involvement and leg spasticity (HBSL), as well as the identification of compound-heterozygous and homozygous mutations in cytoplasmic aspartyl-tRNA synthetase (DARS). These mutations cause nonsynonymous changes to seven highly conserved amino acids, five of which are unchanged between yeast and man, in the DARS C-terminal lobe adjacent to, or within, the active-site pocket. Intriguingly, HBSL bears a striking resemblance to leukoencephalopathy with brain stem and spinal cord involvement and elevated lactate (LBSL), which is caused by mutations in the mitochondria-specific DARS2, suggesting that these two diseases might share a common underlying molecular pathology. These findings add to the growing body of evidence that mutations in tRNA synthetases can cause a broad range of neurologic disorders.

An open-label Phase I/II clinical trial of pyrimethamine for the treatment of patients affected with chronic GM2 gangliosidosis (Tay-Sachs or Sandhoff variants)

Late-onset GM2 gangliosidosis is an autosomal recessive, neurodegenerative, lysosomal storage disease, caused by deficiency of ß-hexosaminidase A (Hex A), resulting from mutations in the HEXA (Tay-Sachs variant) or the HEXB (Sandhoff variant) genes. The enzyme deficiency in many patients with juvenile or adult onset forms of the disease results from the production of an unstable protein, which becomes targeted for premature degradation by the quality control system of the smooth endoplasmic reticulum and is not transported to lysosomes. In vitro studies have shown that many mutations in either the α or β subunit of Hex A can be partially rescued, i.e. enhanced levels of both enzyme protein and activity in lysosomes, following the growth of patient cells in the presence of the drug, pyrimethamine. The objectives of the present clinical trial were to establish the tolerability and efficacy of the treatment of late-onset GM2 gangliosidosis patients with escalating doses of pyrimethamine, to a maximum of 100 mg per day, administered orally in a single daily dose, over a 16-week period . The primary objective, tolerability, was assessed by regular clinical examinations, along with a panel of hematologic and biochemical studies. Although clinical efficacy could not be assessed in this short trial, treatment efficacy was evaluated by repeated measurements of leukocyte Hex A activity, expressed relative to the activity of lysosomal ß-glucuronidase. A total of 11 patients were enrolled, 8 males and 3 females, aged 23 to 50 years. One subject failed the initial screen, another was omitted from analysis because of the large number of protocol violations, and a third was withdrawn very early as a result of adverse events which were not drug-related. For the remaining 8 subjects, up to a 4-fold enhancement of Hex A activity at doses of 50 mg per day or less was observed. Additionally marked individual variations in the pharmacokinetics of the drug among the patients were noted. However, the study also found that significant side effects were experienced by most patients at or above 75 mg pyrimethamine per day. We concluded that pyrimethamine treatment enhances leukocyte Hex A activity in patients with late-onset GM2 gangliosidosis at doses lower than those associated with unacceptable side effects. Further plans are underway to extend these trials and to develop methods to assess clinical efficacy.

Algorithm for the early diagnosis and treatment of patients with cross reactive immunologic material-negative classic infantile pompe disease: a step towards improving the efficacy of ERT.

Objective Although enzyme replacement therapy (ERT) is a highly effective therapy, CRIM-negative (CN) infantile Pompe disease (IPD) patients typically mount a strong immune response which abrogates the efficacy of ERT, resulting in clinical decline and death. This study was designed to demonstrate that immune tolerance induction (ITI) prevents or diminishes the development of antibody titers, resulting in a better clinical outcome compared to CN IPD patients treated with ERT monotherapy. Methods We evaluated the safety, efficacy and feasibility of a clinical algorithm designed to accurately identify CN IPD patients and minimize delays between CRIM status determination and initiation of an ITI regimen (combination of rituximab, methotrexate and IVIG) concurrent with ERT. Clinical and laboratory data including measures of efficacy analysis for response to ERT were analyzed and compared to CN IPD patients treated with ERT monotherapy. Results Seven CN IPD patients were identified and started on the ITI regimen concurrent with ERT. Median time from diagnosis of CN status to commencement of ERT and ITI was 0.5 months (range: 0.1–1.6 months). At baseline, all patients had significant cardiomyopathy and all but one required respiratory support. The ITI regimen was safely tolerated in all seven cases. Four patients never seroconverted and remained antibody-free. One patient died from respiratory failure. Two patients required another course of the ITI regimen. In addition to their clinical improvement, the antibody titers observed in these patients were much lower than those seen in ERT monotherapy treated CN patients. Conclusions The ITI regimen appears safe and efficacious and holds promise in altering the natural history of CN IPD by increasing ERT efficacy. An algorithm such as this substantiates the benefits of accelerated diagnosis and management of CN IPD patients, thus, further supporting the importance of early identification and treatment initiation with newborn screening for IPD.

Clinical Features of Lysosomal Acid Lipase Deficiency

Objective: The aim of this study was to characterize key clinical manifestations of lysosomal acid lipase deficiency (LAL D) in children and adults. Methods: Investigators reviewed medical records of LAL D patients ages ≥5 years, extracted historical data, and obtained prospective laboratory and imaging data on living patients to develop a longitudinal dataset. Results: A total of 49 patients were enrolled; 48 had confirmed LAL D. Mean age at first disease-related abnormality was 9.0 years (range 0–42); mean age at diagnosis was 15.2 years (range 1–46). Twenty-nine (60%) were male patients, and 27 (56%) were <20 years of age at the time of consent/assent. Serum transaminases were elevated in most patients with 458 of 499 (92%) of alanine aminotransferase values and 265 of 448 (59%) of aspartate aminotransferase values above the upper limit of normal. Most patients had elevated low-density lipoprotein (64% patients) and total cholesterol (63%) at baseline despite most being on lipid-lowering therapies, and 44% had high-density lipoprotein levels below the lower limit of normal. More than half of the patients with liver biopsies (n = 31, mean age 13 years) had documented evidence of steatosis (87%) and/or fibrosis (52%). Imaging assessments revealed that the median liver volume was ∼1.15 multiples of normal (MN) and median spleen volume was ∼2.2 MN. Six (13%) patients had undergone a liver transplant (ages 9–43.5 years). Conclusion: This study provides the largest longitudinal case review of patients with LAL D and confirms that LAL D is predominantly a pediatric disease causing early and progressive hepatic dysfunction associated with dyslipidemia that often leads to liver failure and transplantation.

International guidelines for the management and treatment of Morquio A syndrome.

Morquio A syndrome (mucopolysaccharidosis IVA) is a lysosomal storage disorder associated with skeletal and joint abnormalities and significant non‐skeletal manifestations including respiratory disease, spinal cord compression, cardiac disease, impaired vision, hearing loss, and dental problems. The clinical presentation, onset, severity and progression rate of clinical manifestations of Morquio A syndrome vary widely between patients. Because of the heterogeneous and progressive nature of the disease, the management of patients with Morquio A syndrome is challenging and requires a multidisciplinary approach, involving an array of specialists. The current paper presents international guidelines for the evaluation, treatment and symptom‐based management of Morquio A syndrome. These guidelines were developed during two expert meetings by an international panel of specialists in pediatrics, genetics, orthopedics, pulmonology, cardiology, and anesthesia with extensive experience in managing Morquio A syndrome.

Complex II deficiency--a case report and review of the literature.

Complex II deficiency is a rare cause of mitochondrial respiratory chain defects with a prevalence of 2–23%. It is exclusively nuclear encoded and functions in the citric acid cycle by oxidizing succinate to fumarate and in the mitochondrial electron transport chain (ETC) by transferring electrons to ubiquinone. Of the four subunits, SDHA and SDHB are catalytic and SDHC and SDHD are anchoring. Mutations in SDHA and SDHAF1 (assembly factor) have been found in patients with CII deficiency and a mitochondrial phenotype. We present a patient with CII deficiency with a previously undescribed phenotype of dilated cardiomyopathy, left ventricular noncompaction, failure to thrive, hypotonia, and developmental delay. Also, a comprehensive review of 36 cases published in the literature was undertaken. The results show that CII deficiency has a variable phenotype with no correlation with residual complex activity in muscle although the phenotype and enzyme activities are comparable within a family. For some, the condition was fatal in infancy, others had multisystem involvement and some had onset in adulthood with mild symptoms and normal cognition. Neurological involvement is most commonly observed and brain imaging commonly shows leukoencephalopathy, Leigh syndrome, or cerebellar atrophy. Mutations in SDHAF1 are associated with leukoencephalopathy. Other organ systems like heart, muscle, and eyes are only involved in about 50% of the cases but cardiomyopathy is associated with high mortality and morbidity. In some patients, riboflavin has provided clinical improvement.

Clinical, enzymatic and molecular characterization of nine new patients with malonyl-coenzyme A decarboxylase deficiency

SummaryWe report nine new patients with malonic aciduria associated with enzyme-confirmed malonyl-CoA decarboxylase (MCD) deficiency in eight. Clinical details were available on eight, and molecular genetic characterization was obtained for nine. As for 15 previously described patients, cardinal clinical manifestations included developmental delay and cardiomyopathy; metabolic perturbations (e.g. acidosis) and seizures, however, were infrequent or not observed in our patients. For all, detection of elevated malonic acid in urine (± increased C3DC acylcarnitine by analysis employing tandem mass spectrometry) led to pursuit of enzyme studies. MCD activities (nmol/h PER mg protein) revealed: control (n = 22), 16.2 ± 1.8 (SEM; range 5.7–46.2); patients (n = 8, assayed in duplicate), 1.7 ± 0.3 (10% of parallel control; range 0.6–2.8). Molecular characterization by DNA sequence analysis and multiplex ligation-dependent probe amplification revealed nine novel mutations (c.796C>T; p.Gln266X, c.481delC; p.Leu161CysfsX18, c.1367A>C; p.Tyr456Ser, c.1319G>T; p.Ser440Ile, c.1430C>T; p.Ser477Phe, c.899G>T; p.Gly300Val, c.799–1683_949–1293del3128, and two other large genomic deletions comprising exons 1 or the complete gene) and two known mutations in the MLYCD gene. Our findings increase the number of enzyme-confirmed MCD-deficient patients by >50%, and expand our understanding of the phenotypic and molecular heterogeneity of this rare disorder.

Complex V TMEM70 deficiency results in mitochondrial nucleoid disorganization

Mutations in the TMEM70 gene are responsible for a familial form of complex V deficiency presenting with 3-methylglutaconic aciduria, lactic acidosis, cardiomyopathy and mitochondrial myopathy. Here we present a case of TMEM70 deficiency due to compound heterozygous mutations, who displayed abnormal mitochondria with whorled cristae in muscle. Immunogold electron microscopy and tomography shows for the first time that nucleoid clusters of mtDNA are disrupted in the abnormal mitochondria, with both nucleoids and mitochondrial respiratory chain complexes confined to the outer rings of the whorls. This could explain the differential effects on the expression and assembly of complex V in different tissues.

Novel mutations in dihydrolipoamide dehydrogenase deficiency in two cousins with borderline-normal PDH complex activity†

We have diagnosed dihydrolipoamide dehydrogenase (DLD) deficiency in two male second cousins, who presented with markedly different clinical phenotypes. Patient 1 had a recurrent encephalopathy, and patient 2 had microcephaly and lactic acidosis. Their presentation is unusual, in that the DLD subunit deficiency had little effect on pyruvate dehydrogenase complex activity, but caused a severe reduction in the activities of other enzymes that utilize this subunit. We have identified two mutations in the DLD gene in each patient. The second cousins have one novel mutation in common resulting in a substitution of isoleucine for threonine (I47T), which has not been previously reported in the literature. Patient 1 has a second mutation that has been reported to be common in the Ashkenazi Jewish population, G229C. Patient 2 has a second mutation, E375K, which has also been previously reported in the literature. Enzyme kinetic measurements on patient fibroblasts show that under certain conditions, one heteroallelic mutation may have a higher Km. This may account for the differing clinical phenotypes. These findings have important repercussions for other patients with similar clinical phenotypes, as DLD activity is not normally measured in cases with normal PDHc activity.

Vici syndrome associated with sensorineural hearing loss and evidence of neuromuscular involvement on muscle biopsy

Vici syndrome is a rare, genetically unresolved congenital multisystem disorder comprising agenesis of the corpus callosum, cataracts, immunodeficiency, cardiomyopathy, and hypopigmentation. An associated neuromuscular phenotype has not previously been described in detail. We report on an infant with clinical features suggestive of Vici syndrome and additional sensorineural hearing loss. Muscle biopsy revealed several changes including markedly increased variability in fiber size, increased internal nuclei, and abnormalities on Gomori trichrome and oxidative stains, raising a wide differential diagnosis including neurogenic atrophy, centronuclear myopathy (CNM) or a metabolic (mitochondrial) cytopathy. Respiratory chain enzyme studies, however, were normal and sequencing of common CNM‐associated genes did not reveal any mutations. This case expands the clinical spectrum of Vici syndrome and indicates that muscle biopsy ought to be considered in infants presenting with suggestive clinical features. In addition, we suggest that Vici syndrome is considered in the differential diagnosis of infants presenting with congenital callosal agenesis and that additional investigation has to address the possibility of associated ocular, auditory, cardiac, and immunologic involvement when this radiologic finding is present.