Drago Bratkovic

Treatment of Fabry’s Disease with the Pharmacologic Chaperone Migalastat

BACKGROUND Fabrys disease, an X-linked disorder of lysosomal α-galactosidase deficiency, leads to substrate accumulation in multiple organs. Migalastat, an oral pharmacologic chaperone, stabilizes specific mutant forms of α-galactosidase, increasing enzyme trafficking to lysosomes. METHODS The initial assay of mutant α-galactosidase forms that we used to categorize 67 patients with Fabrys disease for randomization to 6 months of double-blind migalastat or placebo (stage 1), followed by open-label migalastat from 6 to 12 months (stage 2) plus an additional year, had certain limitations. Before unblinding, a new, validated assay showed that 50 of the 67 participants had mutant α-galactosidase forms suitable for targeting by migalastat. The primary end point was the percentage of patients who had a response (≥50% reduction in the number of globotriaosylceramide inclusions per kidney interstitial capillary) at 6 months. We assessed safety along with disease substrates and renal, cardiovascular, and patient-reported outcomes. RESULTS The primary end-point analysis, involving patients with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy, did not show a significant treatment effect: 13 of 32 patients (41%) who received migalastat and 9 of 32 patients (28%) who received placebo had a response at 6 months (P=0.30). Among patients with suitable mutant α-galactosidase who received migalastat for up to 24 months, the annualized changes from baseline in the estimated glomerular filtration rate (GFR) and measured GFR were -0.30±0.66 and -1.51±1.33 ml per minute per 1.73 m(2) of body-surface area, respectively. The left-ventricular-mass index decreased significantly from baseline (-7.7 g per square meter; 95% confidence interval [CI], -15.4 to -0.01), particularly when left ventricular hypertrophy was present (-18.6 g per square meter; 95% CI, -38.2 to 1.0). The severity of diarrhea, reflux, and indigestion decreased. CONCLUSIONS Among all randomly assigned patients (with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy), the percentage of patients who had a response at 6 months did not differ significantly between the migalastat group and the placebo group. (Funded by Amicus Therapeutics; ClinicalTrials.gov numbers, NCT00925301 [study AT1001-011] and NCT01458119 [study AT1001-041].).

Phenotype and genotype in 101 males with X-linked creatine transporter deficiency

Background Creatine transporter deficiency is a monogenic cause of X-linked intellectual disability. Since its first description in 2001 several case reports have been published but an overview of phenotype, genotype and phenotype–genotype correlation has been lacking. Methods We performed a retrospective study of clinical, biochemical and molecular genetic data of 101 males with X-linked creatine transporter deficiency from 85 families with a pathogenic mutation in the creatine transporter gene (SLC6A8). Results and conclusions Most patients developed moderate to severe intellectual disability; mild intellectual disability was rare in adult patients. Speech language development was especially delayed but almost a third of the patients were able to speak in sentences. Besides behavioural problems and seizures, mild to moderate motor dysfunction, including extrapyramidal movement abnormalities, and gastrointestinal problems were frequent clinical features. Urinary creatine to creatinine ratio proved to be a reliable screening method besides MR spectroscopy, molecular genetic testing and creatine uptake studies, allowing definition of diagnostic guidelines. A third of patients had a de novo mutation in the SLC6A8 gene. Mothers with an affected son with a de novo mutation should be counselled about a recurrence risk in further pregnancies due to the possibility of low level somatic or germline mosaicism. Missense mutations with residual activity might be associated with a milder phenotype and large deletions extending beyond the 3′ end of the SLC6A8 gene with a more severe phenotype. Evaluation of the biochemical phenotype revealed unexpected high creatine levels in cerebrospinal fluid suggesting that the brain is able to synthesise creatine and that the cerebral creatine deficiency is caused by a defect in the reuptake of creatine within the neurones.

Hematopoietic Stem-Cell Gene Therapy for Cerebral Adrenoleukodystrophy

BACKGROUND In X‐linked adrenoleukodystrophy, mutations in ABCD1 lead to loss of function of the ALD protein. Cerebral adrenoleukodystrophy is characterized by demyelination and neurodegeneration. Disease progression, which leads to loss of neurologic function and death, can be halted only with allogeneic hematopoietic stem‐cell transplantation. METHODS We enrolled boys with cerebral adrenoleukodystrophy in a single‐group, open‐label, phase 2–3 safety and efficacy study. Patients were required to have early‐stage disease and gadolinium enhancement on magnetic resonance imaging (MRI) at screening. The investigational therapy involved infusion of autologous CD34+ cells transduced with the elivaldogene tavalentivec (Lenti‐D) lentiviral vector. In this interim analysis, patients were assessed for the occurrence of graft‐versus‐host disease, death, and major functional disabilities, as well as changes in neurologic function and in the extent of lesions on MRI. The primary end point was being alive and having no major functional disability at 24 months after infusion. RESULTS A total of 17 boys received Lenti‐D gene therapy. At the time of the interim analysis, the median follow‐up was 29.4 months (range, 21.6 to 42.0). All the patients had gene‐marked cells after engraftment, with no evidence of preferential integration near known oncogenes or clonal outgrowth. Measurable ALD protein was observed in all the patients. No treatment‐related death or graft‐versus‐host disease had been reported; 15 of the 17 patients (88%) were alive and free of major functional disability, with minimal clinical symptoms. One patient, who had had rapid neurologic deterioration, had died from disease progression. Another patient, who had had evidence of disease progression on MRI, had withdrawn from the study to undergo allogeneic stem‐cell transplantation and later died from transplantation‐related complications. CONCLUSIONS Early results of this study suggest that Lenti‐D gene therapy may be a safe and effective alternative to allogeneic stem‐cell transplantation in boys with early‐stage cerebral adrenoleukodystrophy. Additional follow‐up is needed to fully assess the duration of response and long‐term safety. (Funded by Bluebird Bio and others; STARBEAM ClinicalTrials.gov number, NCT01896102; ClinicalTrialsRegister.eu number, 2011‐001953‐10.)

Familial 22q11.2 duplication: a three-generation family with a 3-Mb duplication and a familial 1.5-Mb duplication

We report two familial cases of 22q11.2 duplication detected using multiplex ligation‐dependent probe amplification (MLPA). In the first case, eight individuals from a three‐generation family were found to carry a 3‐Mb 22q11.2 duplication. The individuals carrying the duplication show phenotypic variation. This phenotypic variation includes heart defect (1 in 8 individuals, 1/8), submucous cleft palate (2/8), intellectual disability (2/8), speech delay (2/8), behaviour problems (3/8) and brachydactyly (3/8). In the second case, a 1.5‐Mb 22q11.2 duplication was detected in a neonate and her normal mother. The neonate presented with severe laryngomalacia causing intermittent stridor. Cranial ultrasound showed small subependymal cysts bilaterally. There was no heart defect or cleft palate, her chest X ray and renal ultrasound were normal. Review at 2 months of age revealed normal growth and development. Our findings broaden the understanding of 22q11.2 duplication syndrome and demonstrate that MLPA is sensitive for detection and sizing of 22q11.2 microduplications.

Short stature due to 15q26 microdeletion involving IGF1R: Report of an additional case and review of the literature†

Short Stature due to 15q26 Microdeletion Involving IGF1R: Report of an Additional Case and Review of the Literature Laura I. Rudaks, Jillian K. Nicholl, Drago Bratkovic, and Christopher P. Barnett* SA Clinical Genetics Service, Women’s and Children’s Hospital, North Adelaide, South Australia, Australia Cytogenetics Unit, Genetics and Molecular Pathology, Women’s and Children’s Hospital, North Adelaide, South Australia, Australia Metabolic Unit, SA Clinical Genetics Service, Women’s and Children’s Hospital, North Adelaide, South Australia, Australia

Phenotypic Variation of TTC19- Deficient Mitochondrial Complex III Deficiency: A Case Report and Literature Review

Isolated mitochondrial respiratory chain complex III deficiency has been described in a heterogeneous group of clinical presentations in children and adults. It has been associated with mutations in MT‐CYB, the only mitochondrial DNA encoded subunit, as well as in nine nuclear genes described thus far: BCS1L, TTC19, UQCRB, UQCRQ, UQCRC2, CYC1, UQCC2, LYRM7, and UQCC3. BCS1L, TTC19, UQCC2, LYRM7, and UQCC3 are complex III assembly factors. We report on an 8‐year‐old girl born to consanguineous Iraqi parents presenting with slowly progressive encephalomyopathy, severe failure to thrive, significant delays in verbal and communicative skills and bilateral retinal cherry red spots on fundoscopy. SNP array identified multiple regions of homozygosity involving 7.5% of the genome. Mutations in the TTC19 gene are known to cause complex III deficiency and TTC19 was located within the regions of homozygosity. Sequencing of TTC19 revealed a homozygous nonsense mutation at exon 6 (c.937C > T; p.Q313X). We reviewed the phenotypes and genotypes of all 11 patients with TTC19 mutations leading to complex III deficiency (including our case). The consistent features noted are progressive neurodegeneration with Leigh‐like brain MRI abnormalities. Significant variability was observed however with the age of symptom onset and rate of disease progression. The bilateral retinal cherry red spots and failure to thrive observed in our patient are unique features, which have not been described, in previously reported patients with TTC19 mutations. Interestingly, all reported TTC19 mutations are nonsense mutations. The severity of clinical manifestations however does not specifically correlate with the residual complex III enzyme activities.

A 1q44 deletion, paternal UPD of chromosome 2 and a deletion due to a complex translocation detected in children with abnormal phenotypes using new SNP array technology

Children with intellectual disability, dysmorphic features, malformations and/or growth abnormalities frequently display normal karyotypes. Recent studies have shown that genome-wide single nucleotide polymorphism (SNP) arrays can be effective in detecting abnormalities involving copy number variation (CNV), deletions, duplications and loss of heterozygosity (LOH) that routine cytogenetic tests fail to identify. Five patients with various degrees of intellectual disability and/or dysmorphic features and other malformations were whole-genome genotyped using the Human-1 Genotyping BeadChip – Exon-Centrix 100K SNP arrays (Illumina). All patients had undergone routine cytogenetic testing; four patients had normal karyotypes, while one patient had an apparently balanced complex translocation involving chromosomes 1q25, 1q32, 2q23, 7q22 and 16q24. We detected deletions on chromosome 1q44 and 13q31.1 in one patient, and LOH of the entire chromosome 2 in another patient, both with cytogenetically normal karyotypes. The patient with the complex translocation had a deletion on chromosome 7q22.2-22.3, which is in conjunction with one of the translocation breakpoints. Our findings provide further evidence of there being a critical region for the development of microcephaly and corpus callosum abnormalities in children with distal 1q deletions. We have also shown that apparently balanced complex translocations might not be balanced at the DNA level, and we report the fourth case of paternal uniparental disomy of chromosome 2. The results of this study suggest that it may be desirable to investigate idiopathic mental retardation using genome-wide SNP arrays, in conjunction with other cytogenetic and molecular techniques.

Unique presentation of cutis laxa with Leigh-like syndrome due to ECHS1 deficiency

Clinical finding of cutis laxa, characterized by wrinkled, redundant, sagging, nonelastic skin, is of growing significance due to its occurrence in several different inborn errors of metabolism (IEM). Metabolic cutis laxa results from Menkes syndrome, caused by a defect in the ATPase copper transporting alpha (ATP7A) gene; congenital disorders of glycosylation due to mutations in subunit 7 of the component of oligomeric Golgi (COG7)–congenital disorders of glycosylation (CDG) complex; combined disorder of N- and O-linked glycosylation, due to mutations in ATPase H+ transporting V0 subunit a2 (ATP6VOA2) gene; pyrroline-5-carboxylate reductase 1 deficiency; pyrroline-5-carboxylate synthase deficiency; macrocephaly, alopecia, cutis laxa, and scoliosis (MACS) syndrome, due to Ras and Rab interactor 2 (RIN2) mutations; transaldolase deficiency caused by mutations in the transaldolase 1 (TALDO1) gene; Gerodermia osteodysplastica due to mutations in the golgin, RAB6-interacting (GORAB or SCYL1BP1) gene; and mitogen-activated pathway (MAP) kinase defects, caused by mutations in several genes [protein tyrosine phosphatase, non-receptor-type 11 (PTPN11), RAF, NF, HRas proto-oncogene, GTPase (HRAS), B-Raf proto-oncogene, serine/threonine kinase (BRAF), MEK1/2, KRAS proto-oncogene, GTPase (KRAS), SOS Ras/Rho guanine nucleotide exchange factor 2 (SOS2), leucine rich repeat scaffold protein (SHOC2), NRAS proto-oncogene, GTPase (NRAS), and Raf-1 proto-oncogene, serine/threonine kinase (RAF1)], which regulate the Ras-MAPK cascade. Here, we further expand the list of inborn errors of metabolism associated with cutis laxa by describing the clinical presentation of a 17-month-old girl with Leigh-like syndrome due to enoyl coenzyme A hydratase, short chain, 1, mitochondria (ECHS1) deficiency, a mitochondrial matrix enzyme that catalyzes the second step of the beta-oxidation spiral of fatty acids and plays an important role in amino acid catabolism, particularly valine.

Diaphragmatic Eventration in Sisters with Asparagine Synthetase Deficiency: A Novel Homozygous ASNS Mutation and Expanded Phenotype.

BACKGROUND Asparagine Synthetase Deficiency (ASNSD; OMIM #615574) is a newly described rare autosomal recessive neurometabolic disorder, characterised by congenital microcephaly, severe psychomotor delay, encephalopathy and progressive cerebral atrophy. To date, seven families and seven missense mutations in the ASNSD disease causing gene, ASNS, have been published. METHODS We report two further affected infant sisters from a consanguineous Indian family, who in addition to the previously described features had diaphragmatic eventration. Both girls died within the first 6 months of life. Whole exome sequencing (WES) was performed for both sisters to identify the pathogenic mutation. The clinical and biochemical parameters of our patient are compared to previous reports. RESULTS WES demonstrated a homozygous novel missense ASNS mutation, c.1019G > A, resulting in substitution of the highly conserved arginine residue by histidine (R340H). CONCLUSION This report expands the phenotypic and mutation spectrum of ASNSD, which should be considered in neonates with congenital microcephaly, seizures and profound neurodevelopmental delay. The presence of diaphragmatic eventration suggests extracranial involvement of the central nervous system in a disorder that was previously thought to exclusively affect the brain. Like all previously reported patients, these cases were diagnosed with WES, highlighting the clinical utility of next generation sequencing in the diagnosis of rare, difficult to recognise disorders.

Leigh Syndrome Caused by the MT-ND5 m.13513G>A Mutation: A Case Presenting with WPW-Like Conduction Defect, Cardiomyopathy, Hypertension and Hyponatraemia

Mitochondrial disease can present with a wide range of clinical phenotypes, and knowledge of the clinical spectrum of mitochondrial DNA mutation is constantly expanding. Leigh syndrome (LS) has been reported to be caused by the m.13513G>A mutation in the ND5 subunit of complex I (MT-ND5 m.13513G>A). We present a case of a 12-month-old infant initially diagnosed with tachyarrhythmia requiring defibrillation, subsequent presentation with hypertension and hyponatraemia secondary to renal salt loss and presumed inappropriate ADH secretion. Complex I activity in the muscle tissue was 54%, and mutation load in the muscle and lymphocytes was 50%. This case of Leigh syndrome caused by the m.13513G>A mutation in the ND5 gene illustrates that hyponatraemia due to renal sodium loss and inappropriate ADH secretion and hypertension can be features of this entity in addition to the previously reported cardiomyopathy and WPW-like conduction pattern and that they present additional challenges in diagnosis and management.