Hatice Serap Sivri

Identification of Mutations and Evaluation of Cardiomyopathy in Turkish Patients with Primary Carnitine Deficiency

Primary systemic carnitine deficiency (SCD) is an autosomal recessive disorder caused by defective cellular carnitine transport. Patients usually present with predominant metabolic or cardiac manifestations. SCD is caused by mutations in the organic cation/carnitine transporter OCTN2 (SLC22A5) gene. Mutation analysis of SLC22A5 gene was carried out in eight Turkish patients from six families. Six patients presented with signs and symptoms of heart failure, cardiomyopathy, and low plasma carnitine levels, five of them with concurrent anemia. A patient with dilated cardiomyopathy had also facial dysmorphia, microcephaly, and developmental delay. Tandem MS analyses in siblings of the patients revealed two more cases with low plasma carnitine levels. SCD diagnosis was confirmed in these two cases by mutation screening. These two cases were asymptomatic but echocardiography revealed left ventricular dilatation in one of them. Carnitine treatment was started before the systemic signs and symptoms developed in these patients. Mean value of serum carnitine levels of the patients was 2.63±1.92μmol/L at the time of diagnosis. After 1year of treatment, carnitine values increased to 16.62±5.11 (p<0.001) and all responded to carnitine supplementation clinically. Mutation screening of the OCTN2 gene study in the patients revealed two novel (p.G411V, p.G152R), and four previously identified mutations (p.R254X, p.R282X, p.R289X, p.T337Pfs12X). Early recognition and carnitine supplementation can be lifesaving in this inborn error of fatty acid oxidation.

Prevalence of Anti–Adeno-Associated Virus Serotype 8 Neutralizing Antibodies and Arylsulfatase B Cross-Reactive Immunologic Material in Mucopolysaccharidosis VI Patient Candidates for a Gene Therapy Trial

Abstract Recombinant vectors based on adeno-associated virus serotype 8 (AAV8) have been successfully used in the clinic and hold great promise for liver-directed gene therapy. Preexisting immunity against AAV8 or the development of antibodies against the therapeutic transgene product might negatively affect the outcomes of gene therapy. In the prospect of an AAV8-mediated, liver-directed gene therapy clinical trial for mucopolysaccharidosis VI (MPS VI), a lysosomal storage disorder caused by arylsulfatase B (ARSB) deficiency, we investigated in a multiethnic cohort of MPS VI patients the prevalence of neutralizing antibodies (Nab) to AAV8 and the presence of ARSB cross-reactive immunologic material (CRIM), which will either affect the efficacy of gene transfer or the duration of phenotypic correction. Thirty-six MPS VI subjects included in the study harbored 45 (62.5%) missense, 13 (18%) nonsense, 9 (12.5%) frameshift (2 insertions and 7 deletions), and 5 (7%) splicing ARSB mutations. The detection of ARSB protein in 24 patients out of 34 (71%) was predicted by the type of mutations. Preexisting Nab to AAV8 were undetectable in 19/33 (58%) analyzed patients. Twelve out of 31 patients (39%) tested were both negative for Nab to AAV8 and CRIM-positive. In conclusion, this study allows estimating the number of MPS VI patients eligible for a gene therapy trial by intravenous injections of AAV8.

A Zinc Sulphate-Resistant Acrodermatitis Enteropathica Patient with a Novel Mutation in SLC39A4 Gene

Acrodermatitis enteropathica (AE) is a rare autosomal recessive disorder of zinc deficiency due to an abnormal intestinal zinc transporter. It is characterized by the triad of acral dermatitis, alopecia, and diarrhoea. Once AE is correctly diagnosed, patients are treated with orally administered zinc sulphate. In some patients, relapses occur during adolescence, despite the regular treatment. Here, we discuss the clinical and molecular features of a 13-year-old adolescent girl with acrodermatitis enteropathica who was resistant to high-dose zinc sulphate therapy. We successfully treated the patient with zinc gluconate and vitamin C, and we detected a novel homozygous c.541_551dup (p.Leu186fsX38) mutation in the exon 3 of her SLC39A4 gene.

High prevalence of cerebral venous sinus thrombosis (CVST) as presentation of cystathionine beta-synthase deficiency in childhood: molecular and clinical findings of Turkish probands.

Classical homocystinuria is the most commonly inherited disorder of sulfur metabolism, caused by the genetic alterations in human cystathionine beta-synthase (CBS) gene. In this study, we present comprehensive clinical findings and the genetic basis of homocystinuria in a cohort of Turkish patients. Excluding some CBS mutations, detailed genotype-phenotype correlation for different CBS mutations has not been established in literature. We aimed to make clinical subgroups according to main clinical symptoms and discussed these data together with mutational analysis results from our patients. Totally, 16 different mutations were identified; twelve of which had already been reported, and four are novel (p.N93Y, p.L251P, p.D281V and c.829-2A>T). The probands were classified into three major groups according to the clinical symptoms caused by these mutations. A psychomotor delay was the most common diagnostic symptom (n=12, 46.2% neurological presentation), followed by thromboembolic events (n=6, 23.1% vascular presentation) and lens ectopia, myopia or marfanoid features (n=5, 19.2% connective tissue presentation). Pyridoxine responsiveness was 7.7%; however, with partial responsive probands, the ratio was 53.9%. In addition, five thrombophilic nucleotide changes including MTHFR c.677 C>T and c.1298 A>C, Factor V c.1691 G>A, Factor II c.20210 G>A, and SERPINE1 4G/5G were investigated to assess their contributions to the clinical spectrum. We suggest that the effect of these polymorphisms on clinical phenotype of CBS is not very clear since the distribution of thrombophilic polymorphisms does not differ among specific groups. This study provides molecular findings of 26 Turkish probands with homocystinuria and discusses the clinical presentations and putative effects of the CBS mutations.

Post-mortem detection of FLAD1 mutations in 2 Turkish siblings with hypotonia in early infancy

Inherited defects of vitamin B2 (riboflavin) metabolism may cause different phenotypes with common biochemical markers of multiple acyl-CoA dehydrogenase deficiency (MADD). Most recently, mutations in FLAD1, which encodes flavin adenine dinucleotide (FAD) synthase, has been implicated in MADD with combined respiratory chain deficiency in nine patients. Here, we describe two siblings with FAD synthase deficiency, who were diagnosed post-mortem upon suspicion of this newly-described disease. Hypotonia was evident at two months of age in both infants, followed by feeding difficulties, respiratory distress and death in six months despite partial response to riboflavin. The older sibling had documented lipid storage myopathy and biochemical markers of MADD. Our observations support the previous reports of unexpected riboflavin-responsiveness in frameshift mutations in the second exon of FLAD1 and suggest dysmorphic auricular helix and hypospadias as possible additional clinical features. More reports and studies are needed to better describe and treat FAD synthase deficiency.

372. Prevalence of Anti-AAV8 Neutralizing Antibodies and ARSB Cross-Reactive Immunologic Material in MPS VI Patients Candidates for a Gene Therapy Trial

Recombinant vectors based on adeno-associated virus serotype 8 (AAV8) have been successfully used in the clinic and hold great promise for liver-directed gene therapy. Pre-existing immunity against AAV8 or the development of antibodies against the therapeutic transgene product might negatively affect the outcomes of gene therapy. In the prospect of an AAV8-mediated, liver-directed gene therapy clinical trial for Mucopolysaccharidosis VI (MPS VI), a lysosomal storage disorder due to arylsulfatase B (ARSB) deficiency, we investigated in a multiethnic cohort of MPS VI patients the prevalence of neutralizing antibodies (Nab) to AAV8 and the presence of ARSB cross-reactive immunologic material (CRIM), which will either affect the efficacy of gene transfer or the duration of phenotypic correction. Thirty-six MPS VI subjects included in the study harbored 45 (62.5%) missense, 13 (18%) nonsense, 9 (12.5%) frameshift (2 insertions and 7 deletions), and 5 (7%) splicing ARSB mutations. To the best of our knowledge, four mutations had not been previously described. These include: one missense (c.1178 A>G p.H393R) and three frameshift mutations [883-884duplTT (p.F295FfsX42), c.1036delG (p.E346SfsX11), c.1475delC (pP492LfsX80)] predicted to result in truncated proteins. The detection of ARSB protein in twenty-four patients out of 34 (71%) was predicted by the type of mutations. Pre-existing Nab to AAV8 were undetectable in 19/33 (58%) analyzed patients. Twelve out of 31 patients (39%) tested were both negative for Nab to AAV8 and CRIM-positive. In conclusion, this study allows estimating the number of MPS VI patients eligible for a gene therapy trial by intravenous injections of AAV8.