Enzyme replacement therapy for Fabry disease: some answers but more questions

Fabry disease (FD) is a multisystem, X-linked disorder of glycosphingolipid metabolism caused by enzyme deficiency of α-galactosidase A. Affected patients have symptoms including acroparesthesias, angiokeratomas, and hypohidrosis. More serious manifestations include debilitating pain and gastrointestinal symptoms, proteinuria and gradual deterioration of renal function leading to end-stage renal disease, hypertrophic cardiomyopathy, and stroke. Heterozygous females may have symptoms as severe as males with the classic phenotype. Before 2001, treatment of patients with FD was supportive. The successful development of enzyme replacement therapy (ERT) has been a great advancement in the treatment of patients with FD and can stabilize renal function and cardiac size, as well as improve pain and quality of life of patients with FD. In this review, we have provided a critical appraisal of the literature on the effects of ERT for FD. This analysis shows that data available on the treatment of FD are often derived from studies which are not controlled, rely on surrogate markers, and are of insufficient power to detect differences on hard clinical endpoints. Further studies of higher quality are needed to answer the questions that remain concerning the efficacy of ERT for FD

Primary Hyperparathyroidism: An Overview

Primary hyperparathyroidism is a common condition that affects 0.3% of the general population. Primary and tertiary care specialists can encounter patients with primary hyperparathyroidism, and prompt recognition and treatment can greatly reduce morbidity and mortality from this disease. In this paper we will review the basic physiology of calcium homeostasis and then consider genetic associations as well as common etiologies and presentations of primary hyperparathyroidism. We will consider emerging trends in detection and measurement of parathyroid hormone as well as available imaging modalities for the parathyroid glands. Surgical indications and approach will be reviewed as well as medical management of primary hyperparathyroidism with bisphosphonates and calcimimetics

Lentivector Iterations and Pre-Clinical Scale-Up/Toxicity Testing: Targeting Mobilized CD34+ Cells for Correction of Fabry Disease

Fabry disease is a rare lysosomal storage disorder (LSD). We designed multiple recombinant lentivirus vectors (LVs) and tested their ability to engineer expression of human α-galactosidase A (α-gal A) in transduced Fabry patient CD34+ hematopoietic cells. We further investigated the safety and efficacy of a clinically directed vector, LV/AGA, in both ex vivo cell culture studies and animal models. Fabry mice transplanted with LV/AGA-transduced hematopoietic cells demonstrated α-gal A activity increases and lipid reductions in multiple tissues at 6 months after transplantation. Next we found that LV/AGA-transduced Fabry patient CD34+ hematopoietic cells produced even higher levels of α-gal A activity than normal CD34+ hematopoietic cells. We successfully transduced Fabry patient CD34+ hematopoietic cells with “near-clinical grade” LV/AGA in small-scale cultures and then validated a clinically directed scale-up transduction process in a GMP-compliant cell processing facility. LV-transduced Fabry patient CD34+ hematopoietic cells were subsequently infused into NOD/SCID/Fabry (NSF) mice; α-gal A activity corrections and lipid reductions were observed in several tissues 12 weeks after the xenotransplantation. Additional toxicology studies employing NSF mice xenotransplanted with the therapeutic cell product demonstrated minimal untoward effects. These data supported our successful clinical trial application (CTA) to Health Canada and opening of a “first-in-the-world” gene therapy trial for Fabry disease

Exome Sequencing and the Management of Neurometabolic Disorders

BACKGROUND: Whole-exome sequencing has transformed gene discovery and diagnosis in rare diseases. Translation into disease-modifying treatments is challenging, particularly for intellectual developmental disorder. However, the exception is inborn errors of metabolism, since many of these disorders are responsive to therapy that targets pathophysiological features at the molecular or cellular level. METHODS: To uncover the genetic basis of potentially treatable inborn errors of metabolism, we combined deep clinical phenotyping (the comprehensive characterization of the discrete components of a patient's clinical and biochemical phenotype) with whole-exome sequencing analysis through a semiautomated bioinformatics pipeline in consecutively enrolled patients with intellectual developmental disorder and unexplained metabolic phenotypes. RESULTS: We performed whole-exome sequencing on samples obtained from 47 probands. Of these patients, 6 were excluded, including 1 who withdrew from the study. The remaining 41 probands had been born to predominantly nonconsanguineous parents of European descent. In 37 probands, we identified variants in 2 genes newly implicated in disease, 9 candidate genes, 22 known genes with newly identified phenotypes, and 9 genes with expected phenotypes; in most of the genes, the variants were classified as either pathogenic or probably pathogenic. Complex phenotypes of patients in five families were explained by coexisting monogenic conditions. We obtained a diagnosis in 28 of 41 probands (68%) who were evaluated. A test of a targeted intervention was performed in 18 patients (44%). CONCLUSIONS: Deep phenotyping and whole-exome sequencing in 41 probands with intellectual developmental disorder and unexplained metabolic abnormalities led to a diagnosis in 68%, the identification of 11 candidate genes newly implicated in neurometabolic disease, and a change in treatment beyond genetic counseling in 44%. (Funded by BC Children's Hospital Foundation and others.)

Mania following acute decompensation in ornithine transcarbamylase deficiency.

Background Ornithine transcarbamylase deficiency is the most common urea cycle disorder and presents an X-linked pattern of inheritance. Both males and females may be affected with variation in severity and age of onset. Psychiatric symptoms, including episodic psychosis, atypical depression, confusion, erratic behavior or delirium, are possible presentations of late-onset disease. Manic behaviors have previously been reported with hyperammonemia induced by valproic acid. Usually, psychiatric behaviors cease with normalization of ammonia levels. Case report We report a family with two males with confirmed late-onset OTC deficiency (and other adult males with unexplained lethal encephalopathy) due to a missense mutation in OTC (c.119G>A; p.R40H). One 29-year-old male individual, with no psychiatric history, presented hypomanic symptoms with a significant shift from his personality in the days following his first major episode of acute decompensation. Ammonia levels were measured as 245, 30, 11, 106, 20, 38 and 17 micromol/L on days 2, 5, 8, 9, 9, 9, and 10, respectively, following the acute crisis onset. Symptoms of vomiting, confusion, tremors and loss of consciousness stopped at day 5. Hypomanic symptoms were noted from day 5 and were finally controlled with long-acting quetiapine ten days after normalization of serum ammonia levels (daily levels were normal from day 10 to day 21). CT scan of the brain was normal. Conclusion Illustrated by this case report, occurrence of mania secondary to a hyperammonic crisis may be the consequence of dysregulated neurotransmission balance in brain, which can persist after normalization of serum ammonia levels

Primary hyperparathyroidism: an overview [published online ahead of print June 2, 2011

Primary hyperparathyroidism is a common condition that affects 0.3% of the general population. Primary and tertiary care specialists can encounter patients with primary hyperparathyroidism, and prompt recognition and treatment can greatly reduce morbidity and mortality from this disease. In this paper we will review the basic physiology of calcium homeostasis and then consider genetic associations as well as common etiologies and presentations of primary hyperparathyroidism. We will consider emerging trends in detection and measurement of parathyroid hormone as well as available imaging modalities for the parathyroid glands. Surgical indications and approach will be reviewed as well as medical management of primary hyperparathyroidism with bisphosphonates and calcimimetics

Primary Hyperparathyroidism: An Overview

Primary hyperparathyroidism is a common condition that affects 0.3% of the general population. Primary and tertiary care specialists can encounter patients with primary hyperparathyroidism, and prompt recognition and treatment can greatly reduce morbidity and mortality from this disease. In this paper we will review the basic physiology of calcium homeostasis and then consider genetic associations as well as common etiologies and presentations of primary hyperparathyroidism. We will consider emerging trends in detection and measurement of parathyroid hormone as well as available imaging modalities for the parathyroid glands. Surgical indications and approach will be reviewed as well as medical management of primary hyperparathyroidism with bisphosphonates and calcimimetics.Peer Reviewe

Impact of hematopoietic stem cell transplantation in glycogen storage disease type Ib: A single-subject research design using 13C-glucose breath test

Background: Glycogen storage disease type Ib (GSD Ib) is an autosomal recessively inherited deficiency of the glucose-6-phosphate translocase (G6PT). Clinical features include a combination of a metabolic phenotype (fasting hypoglycemia, lactic acidosis, hepatomegaly) and a hematologic phenotype with neutropenia and neutrophil dysfunction. Dietary treatment involves provision of starches such as uncooked cornstarch (UCCS) and Glycosade® to provide prolonged enteral supply of glucose. Granulocyte colony-stimulating factor (G-CSF) is the treatment of choice for neutropenia. Because long-term stimulation of hematopoiesis with G-CSF causes serious complications such as splenomegaly, hypersplenism, and osteopenia; hematopoietic stem cell transplantation (HSCT) has been considered in some patients with GSD Ib to correct neutropenia and avoid G-CSF related adverse effects. Whether HSCT also has an effect on the metabolic phenotype and utilization of carbohydrate sources has not been determined. Objective: Our objective was to measure the utilization of starch in a patient with GSD Ib before and after HSCT using the minimally invasive 13C-glucose breath test (13C-GBT). Design: A case of GSD Ib (18y; female) underwent 13C-GBT four times: UCCS (pre-HSCT), UCCS (3, 5 months post-HSCT) and Glycosade® (6 months post-HSCT) with a dose of 80 g administered via nasogastric tube after a 4 h fast according to our patient's fasting tolerance. Breath samples were collected at baseline and every 30 min for 240 min. Rate of CO2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose <4 mmol/L). Biochemical and clinical data were obtained from the medical records as a post-hoc chart review. Results: UCCS utilization was significantly higher in GSD Ib pre-HSCT, which reduced and stabilized 5 months post-HSCT. UCCS and Glycosade® utilizations were low and not different at 5 and 6 months post-HSCT. Blood glucose concentrations were not significantly different at any time point. Conclusions: Findings show that HSCT stabilized UCCS utilization, as reflected by lower and stable glucose oxidation. The results also illustrate the application of 13C-GBT to examine glucose metabolism in response to various carbohydrate sources after other treatment modalities like HSCT in GSD Ib