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Biomedical subjects

D Powars

Publications and source records attributed to D Powars.

At least 19 recordsLinked to original sources
PubMed1995

Neurologic complications after allogeneic marrow transplantation for sickle cell anemia.

Seven of 21 patients with sickle cell anemia developed neurologic complications 5 to 243 days (median, 33 days) after allogeneic marrow transplantation. Among these 7 patients, indications for transplantation included either a past history of stroke (4 patients) or recurrent severe vaso-occlusive events (3 patients). All received marrow from an HLA-identical sibling after preparation with busulfan and cyclophosphamide, and in 4 patients with antithymocyte globulin. Five of 6 patients developing seizures received anticonvulsant and supportive treatment with resolution of neurologic abnormalities. Three patients experienced intracranial bleeding, which was fatal in two. Of the 14 patients free of neurologic complications, 4 patients had experienced stroke before transplantation. However, among all patients with prior stroke, the incidence of intracranial hemorrhage was 38% (3/8), whereas none of the 13 patients without prior stroke developed posttransplant intracranial bleeding (P = .026). We conclude that patients with sickle cell anemia are at increased risk for neurologic complications after marrow ablative therapy and that patients with prior stroke are at increased risk for intracranial hemorrhage. Transplantation of patients before the onset of overt stroke may reduce this risk.

Adolescent↗
PubMed1993

Sickle cell anemia. Beta s gene cluster haplotypes as genetic markers for severe disease expression.

Identification of the beta s gene cluster haplotype and alpha-gene status provides a useful tool for the detection of high-risk patients with sickle cell anemia. Analysis of the relationship of the long-term clinical course to the above parameters has revealed that those with the haplotype designated Senegal have decreased severity, those with the Benin haplotype have intermediate severity, and those with the Central African Republic (CAR) haplotype have the most severe clinical expression. Further modulation of the clinical course occurs with the coinheritance of alpha-thalassemia-2. In both Africa and the United States, the CAR beta s haplotype increased the risk (relative risk, 2.25; 95% confidence interval, 1.41 to 3.87) of developing a complication and death at an early age. Detection of the CAR haplotype identifies the child with sickle cell anemia at risk for a rapid rate of progression of sickle-induced microvasculopathy, ultimately leading to irreversible organ damage during the first three decades of life. In patients with the CAR haplotype, potential curative therapy, such as bone marrow transplantation or gene insertion, should be seriously considered during childhood, before organ failure is clinically evident.

Africa↗
PubMed1990

Delayed intracranial hemorrhage following cerebral infarction in sickle cell anemia.

Clinical and necropsy findings in 11 patients with sickle cell anemia (SS) indicate that intracranial hemorrhage (IH) is a delayed sequela of the same vasculopathy that causes cerebral infarction during childhood. Evidence of prior cerebral infarction during childhood included hemiparesis, seizures, an episode of coma, or mental retardation. Computerized tomography (CT) scans showed cerebral infarcts with lucent areas and dilated ventricles or cerebral atrophy. CT or magnetic resonance imaging (MRI) scans after the intracranial hemorrhage demonstrated intraventricular or intracerebral hemorrhages. Angiography or autopsy in seven patients showed widespread vascular occlusion and narrowing of arterial vessels. Moyamoya with internal carotid artery occlusion was identified in two cases. At the time of the IH, three patients were being treated with prophylactic transfusion regimens. We hypothesize that the central nervous system vasculopathy progresses over time and that arterial narrowing in both large and small vessels secondary to endothelial hyperplasia is followed by neovascularization and hemorrhage. Recognition of this pattern of delayed intracranial hemorrhage following cerebral infarction should encourage more intensive evaluation aimed at developing rational interventional therapy prior to a terminal intracranial hemorrhage.

Adolescent↗
PubMed1988

Sickle cell chronic lung disease: prior morbidity and the risk of pulmonary failure.

Sickle cell chronic lung disease (SCLD) is a prime contributor to mortality in young adult patients with sickle cell disease, especially those with sickle cell anemia (SS). Both perfusion and diffusion defects have been demonstrated, with generalized pulmonary fibrosis and disabling restrictive lung failure. We report 28 cases (25 SS, 1 S beta(0) thalassemia, 1 S beta(+) thalassemia and 1 SO-Arab) which began during the second decade of life and which ended in death by the fourth decade, after an ordered progression to pulmonary failure and cor pulmonale. Myocardial hypoxia with multifocal fibrosis and segmental infarction occurred in more than one-third of the cases and sudden death was a frequent final event. We define 4 stages of SCLD, based on pulmonary function tests, chest roentgenograms, blood gases, and noninvasive cardiac studies; each stage is 2 or 3 years in length, until death ensues in Stage 4. Case-control analysis showed that the significant risk factors associated with SCLD are 1) the total number of acute chest syndrome events in an individual before the onset of SCLD, (p = 0.0001), 2) sickle cell crisis marked by chest pain (p = 0.03) and 3) aseptic necrosis (p = 0.005). Temporal clustering of acute chest syndrome episodes frequently heralds the onset of SCLD. The pulmonary arterial bed, which has low oxygen tension and low pressure in a slow-flow system, is ideally suited to facilitate the polymerization of sickle hemoglobin, causing endothelial damage and culminating in an obstructive arteriolar vasculopathy. Identification of the significant risk factors predictive of SCLD can lead to early diagnosis of the disease; this is the only hope for effective intervention therapy.

Adolescent↗
PubMed1983

Adenocarcinoma of the colon and rectum in the adolescent.

Between 1969 and 1982, seven adolescents (six girls and one boy) with rectal bleeding and other nonspecific intestinal symptoms were diagnosed with biopsy to have colonic or rectal carcinoma. All came from an impoverished urban environment, and two patients were members of a family with a cancer diathesis (Turcot's syndrome). Surgery provided the only successful curative or palliative treatment. Chemotherapy and radiation therapy were unsuccessful in preventing the progression of disease in far-advanced, nonresectable cases. Prompt attention to lower gastrointestinal bleeding and nonspecific abdominal symptoms in adolescents may result in the earlier diagnosis of colorectal malignancy and improved opportunity for definitive surgical cure.

Adenocarcinoma↗
PubMed1983

Is there an increased risk of Haemophilus influenzae septicemia in children with sickle cell anemia?

The risk of Haemophilus influenzae septicemia/meningitis to children who have sickle cell anemia (SS) has been determined to be greater than that seen among normal infants. Of ten bacteriologically proven cases, eight episodes of infection were observed among 234 children with sickle cell anemia (645 person-years), who were less than 5 years of age. There was one case per 69 infants with sickle cell anemia who were less than 18 months old and one case per 36 children with sickle cell anemia between 19 and 59 months of age. Unexpectedly, two infections occurred among 224 children (824 person-years), aged 5 to 9 years; both died. Contrary to the rapid clinical course of pneumococcal infections in children with sickle cell anemia H influenzae septicemia was regularly heralded by a greater than 24-hour prodrome of upper respiratory tract infection, low-grade fever, and otitis media. Three (30%) preventable deaths occurred. Antibiotic therapy for the febrile child with sickle cell anemia must be predicated on the known 400-fold increased risk of pneumococcal septicemia in those less than 5 years old and the fourfold risk of H influenzae septicemia in those less than 9 years of age.

Anemia, Sickle Cell↗
PubMed1982

Identification of eleven human hemoglobin variants by high-performance liquid chromatography: additional data on functional properties and clinical expression.

Eleven abnormal hemoglobins were detected in the course of cord blood screening or in the evaluation of evident hematological problems in individual cases. Identification of the variant in each case was done by high-performance liquid chromatography (HPLC); HPLC provides a rapid, sensitive means for the examination of abnormal hemoglobins. Some of the 11 variants that were identified have been described repeatedly and are included to provide information on the HPLC behavior of tryptic peptides. Others are much rarer. Additional information is provided about the hematological and clinical expression as well as ethnic and geographical distribution of the abnormal hemoglobin.

Chromatography, High Pressure Liquid↗
PubMed1982

An unusual phenotypic expression of Hb-Leiden.

After a boy of Mexican-American descent became jaundiced during treatment of a serious urinary tract infection with an oxidant drug, an extensive hematological examination was made. The important finding was the presence of Hb-Leiden to the extent of less than 3% or about a tenth of the usual percentage. Although inclusion bodies are present in the erythrocytes at all times, his hematological parameters have remained normal. The genetic basis for the unusually small amount of Hb-Leiden in the propositus may be due to the Hb-Leiden gene in an anti-Lepore configuration, that is, and Hb-Leiden gene in cis to the normal beta and delta genes.

Anemia, Hemolytic↗
PubMed1982

A modified life table method to study congenital genetic disorders: an application in sickle cell anemia.

A modified life table procedure is introduced designed to study the survival of patients with congenital genetic disorders with the endpoint defined by a complication or death. It uses the ages of the patients as the time axis as in "population' or "current' life tables, and it allows patients to enter and exit the study as in survival life tables. The procedure uses the exact length of time that each patient is observed in the study to determine the conditional probabilities of developing the complication. The proposed procedure is especially helpful in studying recurrent complications or events that occur frequently. The proposed life table procedure is demonstrated in the study of the conditional probability of developing a sickle cell crisis in 509 patients with sickle cell anemia (SS) with different number of prior crises. The demonstration is intended to illustrate the use of the proposed method and not to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was positively related to the number of prior crises in SS patients (P less than 0.001). This trend was significant in the first three decades of life.

Actuarial Analysis↗
PubMed1982

Evaluation of the surgical aspects of staging laparotomy for Hodgkin's disease in children.

Experience with 72 children in which the type of staging laparotomy recommended by the Intergroup Hodgkin's Disease in Childhood Study (IHDCS) was employed (1967-1981) is reviewed. Laparotomy altered the stage in 35% of these patients including advance in stage (I-II to III-IV) in 24 patients, and reduction in stage (III to II) in one patient. In adults, Stage III disease is divided into III1 and III2 on the basis of the presence or absence of lower abdominal node involvement; and prognosis is significantly better in III1. Nine patients from two additional institutions were included in a special study of Stage III disease. This included 22 children in III1 and 11 children in III2. Although the children with Stage B (systemic symptoms) disease were concentrated in III2, none of the measured difference between these two groups were significant. No fatal postsplenectomy sepsis has been noted since the use of pneumococcal vaccine and prophylactic penicillin became standard.

Abdomen↗
PubMed1982

Neutrophilic phagocytosis in autoimmune thrombocytopenia purpura.

In vivo neutrophil phagocytosis was demonstrated by transmission electron microscopy (TEM) in the peripheral blood of two half-sibs with hereditary thrombocytopenia. These sibs have had a lifetime documented history of thrombocytopenia. Light microscopy morphology and histochemistry studies of blood and marrow were normal, similar studies of blood from available members of the kinship were also normal. Scanning electron microscopy (SEM) of platelets from each member of the kinship showed normal dendritic and spreading formation. In the TEM thin sections of platelet buffy coats, neutrophil ingestion of platelets was common and all stages of the phagocytic process were noted--from platelet-neutrophil intimacy to the formation of myelin bodies in phagosomes. The clinical courses over a 10-year period were mild, requiring rare therapeutic interventions. The chronic thrombocytopenia, lengthy mild course, modestly elevated platelet-associated immune globulin, normal aggregation and survival studies, and autoimmune neutrophil reaction to platelets allowed classification of these patients as hereditary thrombocytopenia purpuras.

Adult↗