Aneal Khan

T1 Mapping With Cardiovascular MRI Is Highly Sensitive for Fabry Disease Independent of Hypertrophy and Sex

Background— Fabry disease (FD) is an X-linked disorder of lysosomal metabolism affecting multiple organs with cardiac disease being the leading cause of death. Current imaging evaluations of the heart are suboptimal. The goals of the current study are to evaluate the potential of quantitative T1 mapping with cardiovascular MRI as a disease-specific imaging biomarker. Methods and Results— A total of 31 patients with FD, 23 healthy controls, and 21 subjects with concentric remodeling or hypertrophy underwent cardiovascular MRI to measure left ventricular (LV) morphology, function, delayed enhancement, as well as myocardial T1 values, and derived parameters (extracellular volume). All subjects had LV ejection fraction >50% and similar volumes. FD and concentric remodeling or hypertrophy had similarly increased mass, wall thickness, and mass/volume as compared with controls. A total of 16 of 31 FD subjects and 10 of 21 concentric remodeling or hypertrophy subjects had LV hypertrophy. Noncontrast myocardial T1 values were substantially lower in FD as compared with controls and concentric remodeling or hypertrophy (1070±50, 1177±27, and 1207±33 ms, respectively; P<0.001), but extracellular volume was similar in all groups (21.7±2.4%, 22.2±3.1%, and 21.8±3.9%, respectively). Single-voxel NMR spectroscopy in 4 FD and 4 healthy control subjects showed a significant negative linear relationship between lipid content and noncontrast T1 values (r=−0.9; P=0.002). Female subjects had lower LV mass and wall thickness, longer myocardial T1 values and larger extracellular volume suggesting a key sex difference in cardiac remodeling. Conclusions— Reduced noncontrast myocardial T1 values are the most sensitive and specific cardiovascular MRI parameter in patients with FD irrespective of sex and LV morphology and function.

T1 Mapping with CMR Is Highly Sensitive for Fabry Disease Independent of Hypertrophy and Gender

Background— Fabry disease (FD) is an X-linked disorder of lysosomal metabolism affecting multiple organs with cardiac disease being the leading cause of death. Current imaging evaluations of the heart are suboptimal. The goals of the current study are to evaluate the potential of quantitative T1 mapping with cardiovascular MRI as a disease-specific imaging biomarker. Methods and Results— A total of 31 patients with FD, 23 healthy controls, and 21 subjects with concentric remodeling or hypertrophy underwent cardiovascular MRI to measure left ventricular (LV) morphology, function, delayed enhancement, as well as myocardial T1 values, and derived parameters (extracellular volume). All subjects had LV ejection fraction >50% and similar volumes. FD and concentric remodeling or hypertrophy had similarly increased mass, wall thickness, and mass/volume as compared with controls. A total of 16 of 31 FD subjects and 10 of 21 concentric remodeling or hypertrophy subjects had LV hypertrophy. Noncontrast myocardial T1 values were substantially lower in FD as compared with controls and concentric remodeling or hypertrophy (1070±50, 1177±27, and 1207±33 ms, respectively; P<0.001), but extracellular volume was similar in all groups (21.7±2.4%, 22.2±3.1%, and 21.8±3.9%, respectively). Single-voxel NMR spectroscopy in 4 FD and 4 healthy control subjects showed a significant negative linear relationship between lipid content and noncontrast T1 values (r=−0.9; P=0.002). Female subjects had lower LV mass and wall thickness, longer myocardial T1 values and larger extracellular volume suggesting a key sex difference in cardiac remodeling. Conclusions— Reduced noncontrast myocardial T1 values are the most sensitive and specific cardiovascular MRI parameter in patients with FD irrespective of sex and LV morphology and function.

Risk factors for fractures and avascular osteonecrosis in type 1 Gaucher disease: a study from the International Collaborative Gaucher Group (ICGG) Gaucher Registry.

We hypothesized that overall disease activity or the severity of involvement of individual disease compartments, as measured by clinical and surrogate markers, predict the risk of avascular osteonecrosis (AVN) or fractures in type 1 Gaucher disease (GD1). We applied our risk‐set matched case‐control method to identify four patient groups within the International Collaborative Gaucher Group (ICGG) Gaucher Registry based on the presence and absence of AVN and fractures. Characteristics of GD1 were examined by comparing the distributions of each risk factor in cases versus matched controls using conditional logistic regression to calculate adjusted odds ratios (OR). Potential risk factors included hematological and visceral parameters, GD1 biomarkers, white blood cells, GBA1 genotype, and spine and femur dual‐energy X‐ray absorptiometry (DXA) Z‐scores. In the total population of 5894 ICGG Gaucher Registry patients, 544 experienced at least one episode of AVN; 2008 reported no history of AVN. Clinical and surrogate markers of disease activity were similar in patients with and without AVN; patients with AVN were 1.6 times more likely to be anemic compared to matched controls (OR = 1.59; 95% confidence interval [CI], 1.06–2.38, p < 0.05). For fractures, 319 patients suffered fractures and 1233 had no prior history of fractures. Clinical and surrogate markers of disease in patients with and without fractures were similar, except for mean lumbar spine DXA Z‐scores. Among patients with fractures, 49.3% had DXA Z‐scores ≤ −1 compared to 31.0% in the control group. Compared to controls with Z‐scores > −1.0, GD1 patients exhibiting Z‐scores ≤ −1 had an OR of 5.55 (95% CI, 1.81–17.02, p < 0.01) for fracture. In GD1, after controlling for gender, year of birth, treatment status, and splenectomy status, we identified new risk factors for AVN and fractures. Concurrent anemia was associated with an increased risk for AVN. Low bone mineral density of the lumbar spine was a strong risk factor for fractures of the spine and femur in GD1.

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.

Mutation Analysis of B3GALTL in Peters Plus Syndrome

Peters Plus syndrome comprises ocular anterior segment dysgenesis (most commonly Peters anomaly), short stature, hand anomalies, distinctive facial features, and often other additional defects and is inherited in an autosomal‐recessive pattern. Mutations in the β1,3‐glucosyltransferase gene (B3GALTL) were recently reported in 20 out of 20 patients with Peters Plus syndrome. In our study, B3GALTL was examined in four patients with typical Peters Plus syndrome and four patients that demonstrated a phenotypic overlap with this condition. Mutations in B3GALTL were identified in all four patients with typical Peters Plus syndrome, while no mutations were found in the remaining four patients that demonstrated some but not all characteristic features of the syndrome. The previously reported common mutation, c.660 + 1G > A, accounted for 75% of the mutant alleles in our Peters Plus syndrome population. In addition, two new mutant alleles, c.459 + 1G > A and c.230insT, were identified and predicted to result in truncated protein products. These data confirm an important role for B3GALTL in causing typical Peters Plus syndrome, and suggest that this gene may not be implicated in syndromic cases that involve Peters anomaly but lack other classic features of this complex condition.

Prenatally diagnosed mosaic trisomy 22 in a fetus with left ventricular non-compaction cardiomyopathy.

Jia-Chi Wang,* Linda Dang, Tapas Kumar Mondal, and Aneal Khan Cytogenetics Laboratory, Hamilton Regional Laboratory Medicine Program, Hamilton Health Sciences, Hamilton, Canada Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada Department of Medical Genetics, University of Calgary, Alberta Children’s Hospital, Calgary, Alberta, Canada

Gender‐specific plasma proteomic biomarkers in patients with Anderson–Fabry disease

Anderson–Fabry disease (AFD) is an important X‐linked metabolic disease resulting in progressive end‐organ involvement, with cardiac disease being the dominant determinant of survival in a gender‐dependent manner. Recent epidemiological screening for AFD suggests the prevalence is much higher than previously recognized, with estimates of 1:3000. Our aim was to discover novel plasma biomarker signatures in adult patients with AFD.

Reducing selection bias in case-control studies from rare disease registries

BackgroundIn clinical research of rare diseases, where small patient numbers and disease heterogeneity limit study design options, registries are a valuable resource for demographic and outcome information. However, in contrast to prospective, randomized clinical trials, the observational design of registries is prone to introduce selection bias and negatively impact the validity of data analyses.The objective of the study was to demonstrate the utility of case-control matching and the risk-set method in order to control bias in data from a rare disease registry. Data from the International Collaborative Gaucher Group (ICGG) Gaucher Registry were used as an example.MethodsA case-control matching analysis using the risk-set method was conducted to identify two groups of patients with type 1 Gaucher disease in the ICGG Gaucher Registry: patients with avascular osteonecrosis (AVN) and those without AVN. The frequency distributions of gender, decade of birth, treatment status, and splenectomy status were presented for cases and controls before and after matching. Odds ratios (and 95% confidence intervals) were calculated for each variable before and after matching.ResultsThe application of case-control matching methodology results in cohorts of cases (i.e., patients with AVN) and controls (i.e., patients without AVN) who have comparable distributions for four common parameters used in subject selection: gender, year of birth (age), treatment status, and splenectomy status. Matching resulted in odds ratios of approximately 1.00, indicating no bias.ConclusionsWe demonstrated bias in case-control selection in subjects from a prototype rare disease registry and used case-control matching to minimize this bias. Therefore, this approach appears useful to study cohorts of heterogeneous patients in rare disease registries.

Neurodegeneration in D-bifunctional protein deficiency: diagnostic clues and natural history using serial magnetic resonance imaging

We report serial neurodegenerative changes on neuroimaging in a rare peroxisomal disease called D-bifunctional protein deficiency. The pattern of posterior to anterior demyelination with white matter disease resembles X-linked adrenoleukodystrophy. We feel this case is important to (1) highlight that D-bifunctional protein deficiency should be considered in cases where the neuroimaging resembles X-linked adrenoleukodystrophy, (2) to show different stages of progression to help identify this disease using neuroimaging in children, and (3) to show that neuroimaging suggesting a leukodystrophy can warrant peroxisomal beta-oxidation studies in skin fibroblasts even when plasma very long chain fatty acids are normal.

Endothelial ultrastructural alterations of intramuscular capillaries in infantile mitochondrial cytopathies: “Mitochondrial angiopathy”

Electron microscopy (EM) is a reliable method for diagnosing mitochondrial diseases in striated muscle biopsy in infancy. Ultrastructural alterations in mitochondria of myofibers are well documented, but there are few studies of endothelial involvement in intramuscular capillaries. Quadriceps femoris biopsies of five representative infants and toddlers, ages neonate to 3.5 years, were performed because of clinical and laboratory data consistent with mitochondrial disease without mitochondrial DNA (mtDNA) mutations and likely with nuclear DNA mutations. Pathological studies included histochemistry, EM, respiratory chain enzymatic assay and mtDNA sequencing and deletion/duplication analysis. EM demonstrated frequent and severe alterations of mitochondria in capillary endothelium. The most constant changes included: either too few or fragmented cristae; stacked and whorled cristae; paracrystallin structures that often were large and spheroid with stress fractures; closely apposed membranes of granular endoplasmic reticulum surrounding mitochondria with loss of the normal intervening layer of cytoplasm; long narrow, thin looped microvilli extending into the lumen; and thick microvilli containing large, abnormal mitochondria. We conclude that mitochondrial cytopathies in early life exhibit more severe ultrastructural alterations in the endothelium than in myofibers and that paracrystallin body structure differs, perhaps due to less rigid surrounding structures. This distribution may explain the frequent lack of prominent histochemical and biochemical abnormalities in muscle biopsies of young patients. Endothelial changes do not distinguish the genetic defects. Vascular involvement in brain contributes to cerebral lesions and neuronal death by impairment of molecular and nutrient transport and ischemia; endothelium in muscle may reflect similar changes.