Theodore J. Pysher

Xq28-linked noncompaction of the left ventricular myocardium: Prenatal diagnosis and pathologic analysis of affected individuals

Isolated noncompaction of the left ventricular myocardium (INVM) is characterized by the presence of numerous prominent trabeculations and deep intertrabecular recesses within the left ventricle, sometimes also affecting the right ventricle and interventricular septum. Familial occurrence of this disorder was described previously. We present a family in which 6 affected individuals demonstrated X-linked recessive inheritance of this trait. Affected relatives presented postnatally with left ventricular failure and arrhythmias, associated with the pathognomonic echocardiographic findings of INVM. The usual findings of Barth syndrome (neutropenia, growth retardation, elevated urinary organic acids, low carnitine levels, and mitochondrial abnormalities) were either absent or found inconsistently. Fetal echocardiograms obtained between 24-30 weeks of gestation in 3 of the affected males showed a dilated left ventricle in one heart, but were not otherwise diagnostic of INVM in any of the cases. Four of the affected individuals died during infancy, one is in cardiac failure at age 8 months, and one is alive following cardiac transplant at age 9 months. The hearts from infants who died or underwent transplantation appeared, on gross examination, to be enlarged, with coarse, deep ventricular trabeculations and prominent endocardial fibroelastosis. Histologically, there were loosely organized fascicles of myocytes in subepicardial and midmyocardial zones of both ventricles, and the myocytes showed thin, often angulated fibers with prominent central clearing and reduced numbers of filaments. Markedly elongated mitochondria were present in some ventricular myocytes from one specimen, but this finding was not reproducible. Genetic linkage analysis has localized INVM to the Xq28 region, where other myopathies with cardiac involvement have been located.

Neonatal, Lethal Noncompaction of the Left Ventricular Myocardium Is Allelic with Barth Syndrome

Loss-of-function mutations in the G4.5 gene have been shown to cause Barth syndrome (BTHS), an X-linked disorder characterized by cardiac and skeletal myopathy, short stature, and neutropenia. We recently reported a family with a severe X-linked cardiomyopathy described as isolated noncompaction of the left ventricular myocardium (INVM). Other findings associated with BTHS (skeletal myopathy, neutropenia, growth retardation, elevated urinary organic acids, and mitochondrial abnormalities) were either absent or inconsistent. A linkage study of the X chromosome localized INVM to the Xq28 region near the BTHS locus, suggesting that these disorders are allelic. We screened the G4.5 gene for mutations in this family with SSCP and direct sequencing and found a novel glycine-to-arginine substitution at position 197. This position is conserved in a homologous Caenorhabditis elegans protein. We conclude that INVM is a severe allelic variant of BTHS with a specific effect on the heart. This finding provides further structure-function information about the G4.5 gene product and has implications for unexplained cases of severe infantile hypertrophic cardiomyopathy in males.

Using VAAST to identify an X-linked disorder resulting in lethality in male infants due to N-terminal acetyltransferase deficiency.

We have identified two families with a previously undescribed lethal X-linked disorder of infancy; the disorder comprises a distinct combination of an aged appearance, craniofacial anomalies, hypotonia, global developmental delays, cryptorchidism, and cardiac arrhythmias. Using X chromosome exon sequencing and a recently developed probabilistic algorithm aimed at discovering disease-causing variants, we identified in one family a c.109T>C (p.Ser37Pro) variant in NAA10, a gene encoding the catalytic subunit of the major human N-terminal acetyltransferase (NAT). A parallel effort on a second unrelated family converged on the same variant. The absence of this variant in controls, the amino acid conservation of this region of the protein, the predicted disruptive change, and the co-occurrence in two unrelated families with the same rare disorder suggest that this is the pathogenic mutation. We confirmed this by demonstrating a significantly impaired biochemical activity of the mutant hNaa10p, and from this we conclude that a reduction in acetylation by hNaa10p causes this disease. Here we provide evidence of a human genetic disorder resulting from direct impairment of N-terminal acetylation, one of the most common protein modifications in humans.

Response to Shiga toxin 1 and 2 in a baboon model of hemolytic uremic syndrome

Abstract.Post-diarrheal (D+) hemolytic uremic syndrome (HUS) is caused by Shiga-toxin (Stx)-producing Escherichia coli. There is epidemiological, cell culture, and mouse model evidence that Stx2-producing E. coli are more likely to cause HUS than strains that produce only Stx1, but this hypothesis has not been tested in a primate model of HUS. We have developed a baboon model of Stx-mediated HUS that was employed to compare the clinical, cytokine, and histological response to equal amounts of the two Shiga toxins. Animals given IV Stx2 developed progressive thrombocytopenia, hemolytic anemia, and azotemia, and urinary interleukin-6 levels rose significantly. Glomerular thrombotic microangiopathy was found at necropsy. Animals given Stx1 showed no cytokine response and no clinical, laboratory, or histological signs of HUS. Our findings from the primate model corroborate previous epidemiological, cell culture, and mouse model observations, and suggest that enteric infection with Stx2-producing E. coli is more likely to cause HUS than infection with organisms that produce only Stx1.

Characterization of the baboon responses to Shiga-like toxin : Descriptive study of a new primate model of toxic responses to Stx-1

The baboon response to intravenous infusion of Shiga toxin 1 (Stx-1) varied from acute renal failure, proteinuria, hyperkalemia, and melena with minimal perturbation of host inflammatory and hemostatic systems (high-dose group, 2.0 microg/kg; n = 5) to renal failure with hematuria, proteinuria, thrombocytopenia, schistocytosis, anemia, and melena (low-dose group, 0.05 to 0.2 microg/kg; n = 8). Both groups exhibited renal shutdown and died in 57 hours or less. Both groups produced urine that was positive for tumor necrosis factor and interleukin-6 although neither of these cytokines was detectable (</=5 ng/ml) in the general circulation. Light and electron microscopy showed organelle disintegration and necrosis of the renal proximal tubular epithelium and of the intestinal mucosal epithelium at the tips of the microvilli, both of which were previously shown to bear Gb3 receptors. The renal distal tubular epithelium was spared. The renal proximal tubular epithelial changes were accompanied by swelling of visceral epithelial cells (podocytes) and by swelling and detachment of endothelial cells of the glomerular capillaries. In addition, all of the animals receiving low-dose Stx-1 showed microvascular fibrin deposition and thrombosis in renal glomerular and peritubular capillaries in association with a fall in hematocrit and platelet count and a rise in schistocyte count. The gastrointestinal villous tip lesions were accompanied by varying degrees of mucosal and submucosal congestion, hemorrhage, or necrosis. Electron microscopic images of cerebral cortex and cerebellum showed diffuse unraveling of myelin sheaths with occasional disintegration of neuronal cell bodies. In contrast to the gastrointestinal mucosal and renal proximal tubular epithelium, the Gb3 receptor glycolipid of the renal glomerular and neuronal tissues as determined using toxin overlay thin-layer chromatography plates was below the limit of detection (<13 pM/g wet tissue). We conclude that, depending on the status of the host and amount of toxin infused, Stx-1 can produce a variety of responses ranging from damage to cells carrying the Gb3 receptor (renal proximal tubular epithelial cells and gastrointestinal mucosa) to damage to renal glomerular tissues with microvascular thrombosis as a result of the hosts inflammatory response localized to the kidney. We conclude that this thrombotic coagulopathy arises from local changes in the kidney because the appearance of host inflammatory mediators was limited to the urine. This suggests that the initial host response is localized in the kidney, and that the systemic thrombocytopenia, anemia, and schistocytosis may arise secondarily.

Is “transfusion-associated necrotizing enterocolitis” an authentic pathogenic entity?

BACKGROUND: Necrotizing enterocolitis (NEC) sometimes occurs after a transfusion, but it is unclear whether this is a chance association or cause and effect.

Predictors of Fatality in Postdiarrheal Hemolytic Uremic Syndrome

OBJECTIVES. Describe the cause of deaths among patients with postdiarrheal hemolytic uremic syndrome (HUS) and identify predictors of death at the time of hospital admission. METHODS. Case-control study of 17 deaths among patients with HUS identified from the Intermountain HUS Patient Registry (1970–2003) compared against all nonfatal cases. RESULTS. Of the 17 total deaths, 15 died during the acute phase of disease. Two died because treatment was withdrawn based on their preexisting conditions, and 1 died because of iatrogenic cardiac tamponade; they were excluded from analysis. Brain involvement was the most common cause of death (8 of 12); congestive heart failure, pulmonary hemorrhage, and hyperkalemia were infrequent causes. Presence of prodromal lethargy, oligoanuria, or seizures and white blood cell count (WBC) >20 × 109/L or hematocrit >23% on admission were predictive of death. In multivariate analysis, elevated WBC and elevated hematocrit were independent predictors. The combination of prodromal dehydration, oliguria, and lethargy and admission WBC values >20 × 109/L and hematocrit >23% appeared in 7 of the 12 acute-phase deaths. CONCLUSIONS. Diarrheal HUS patients presenting with oligoanuria, dehydration, WBC >20 × 109/L, and hematocrit >23% are at substantial risk for fatal hemolytic uremic syndrome. Such individuals should be referred to pediatric tertiary care centers.

A clinicopathological study of 24 children with hemolytic uremic syndrome: a report of the Southwest pediatric nephrology study group

This study reports the pattern of renal injury in 24 North American children with hemolytic uremic syndrome (HUS), and the extent of extrarenal involvement in 9 of these children examined at autopsy. Fifteen of the 24 children were studied during the first 16 days of hospital-ization; their renal specimens demonstrated glomerular thrombotic microangiopathy (TMA) in 8 children, cortical necrosis in 1, and varying degrees of glomerular TMA and cortical necrosis in 6 children. Nine of the children were studied after 16 or more days of hospitalization; these patients had prominent renal arterial lesions. Of 9 children examined at autopsy, extrarenal microthrombi were identified in 8. In 4 children who died during the acute phase of the disease, hemorrhagic colonic necrosis (3 children) and pancreatic islet cell necrosis (2 children) were the principal extrarenal lesions encountered. Rare microthrombi were present in the brains of the 3 children who manifested seizures.

Testing platelet mass versus platelet count to guide platelet transfusions in the neonatal intensive care unit

BACKGROUND: Platelet (PLT) transfusions can bestow significant benefits but they also carry risks. This study sought a safe means of reducing PLT transfusions to neonatal intensive care unit (NICU) patients with thrombocytopenia by comparing two transfusion guidelines, one based on PLT count and the other on PLT mass (PLT count times mean PLT volume).

Clinicopathologic comparison of familial versus sporadic atypical teratoid/rhabdoid tumors (AT/RT) of the central nervous system

Central nervous system (CNS) atypical teratoid/rhabdoid tumors (AT/RT) are aggressive tumors usually diagnosed in young children and characterized by SMARCB1 (INI1, hSNF5) gene abnormalities. Despite initial chemo‐radiation responsiveness, most children die of progressive disease (PD). Little data regarding familial AT/RT clinical course exist. This study described and compared familial (F) versus sporadic (S) AT/RT and elucidated SMARCB1 mutations and inheritance patterns.