Can natural variation in erythroid microRNA‐29b be translated to sickle cell disease severity?

Introduction: Sickle cell disease (SCD) ranks high among genetic disorders worldwide. It is characterised by repeated vaso-occlusion with resultant end-organ damage. This process can occur in all vascular beds in the body, including ocular blood vessels and may cause irreversible blindness in advanced stages. Little is known of the relationship between the prevalence of ocular abnormalities among children with SCD and their disease severity. Methods: A descriptive cross-sectional study was carried out at the Paediatric Haematology Clinics and the Eye Centre of the Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC), Ile-Ife. Children with SCD in steady state were recruited from the Haematology Clinics and examined for ocular abnormalities at the Eye Centre of the hospital. The subjects SCD severity grade was determined using a previously validated scoring system. Results: One hundred and twenty (120) children aged 5 to 15 years were examined. Of these, 72 had one or more ocular abnormalities giving the prevalence of ocular abnormalities among them to be 60.0%. Though a higher proportion of children with moderate disease, 23 (65.7%) of 35, compared to those with mild disease, 49 (57.6%) of 85 had ocular abnormalities, this difference was not statistically significant, p = 0.412. Conclusion: Ocular abnormalities among Nigerian children with SCD are common even in steady-state, but not significantly associated with disease severity. Periodic screening for ocular abnormalities should thus be done on them irrespective of disease severity.

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Severity of Sickle Cell Disease: Modeling Interrelationships among Hemolysis, Pulmonary Hypertension and Risk of Death.

Blood ◽

10.1182/blood.v108.11.786.786 ◽

2006 ◽

Vol 108 (11) ◽

pp. 786-786

Author(s):

Paola Sebastiani ◽

Vikki G. Nolan ◽

Clinton T. Baldwin ◽

Maria M. Abad-Grau ◽

Ling Wang ◽

...

Keyword(s):

Pulmonary Hypertension ◽

Sickle Cell Disease ◽

Disease Severity ◽

Hemolytic Anemia ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Clinical Severity ◽

Acute Chest Syndrome ◽

Cell Disease ◽

Risk Of Death

Abstract A single point mutation in the β hemoglobin gene causes sickle cell disease (SCD), but patients have extremely variable phenotypes. Hemolysis-related complications include pulmonary hypertension (PHT), priapism, stroke and leg ulceration; blood viscosity and sickle vasoocclusion are associated with painful episodes, acute chest syndrome and osteonecrosis. Predicting who is at highest risk of death would be useful therapeutically and prognostically. Applying Bayesian network modeling that describes complex interactions among many variables by factorizing their joint probability distribution into modules, to data from 3380 SCD patients, we constructed a disease severity score (DSS: 0, least severe; 1, most severe), defining severity as risk of death within 5 years. A network of 24 variables described complex associations among clinical and laboratory complications of SCD. The analysis was validated in 140 patients whose SCD severity was assessed by expert clinicians and 210 adults where severity was also assessed by the echocardiographic diagnosis of PHT and death. Information about PHT allowed a comparison of the DSS with the tricuspid regurgitant jet velocity (TRJV), an objective marker of PHT and an independent risk factor for death. DSS and three indices of clinical severity (severity ranking of individuals by expert clinicians; objective measurement of the presence and severity of PHT; risk of prospective death) were correlated. Among living subjects, the median score was 0.57 in 135 patients without PHT, 0.64 in 40 patients with mild PHT and 0.86 in 15 patients with severe PHT. The difference in average score between living patients with and without PHT is significant. The same increasing trend was noticeable in the subjects who died during follow-up: 0.60 in subjects without PHT; 0.68 in subjects with mild PHT; 0.79 in subjects with severe PHT. The utility of the DSS is also supported by the ability to assign a score to subjects for whom the TRJV cannot be measured. Surprisingly, besides known risk factors like renal insufficiency and leukocytosis, we identified the intensity of hemolytic anemia and clinical events associated with hemolytic anemia as contributing to risk for death. Priapism, an excellent reflection of the hemolytic anemia-related complications of SCD, is associated with PHT and its association with death was unexpected. Laboratory variables predictive of disease severity included LDH and reticulocytes that reflect the intensity of hemolytic anemia. Elevated systolic blood pressure increased the odds of death by 3.4, consistent with hypertension as a marker of early death in SCD. Subjects with sickle cell anemia are at greatest risk compared with subjects with sickle cell anemia-α thalassemia and with subjects with HbSC disease. Our model suggests that the intensity of hemolytic anemia, estimated by LDH, reticulocyte count and AST, and shown previously to be associated with PHT, priapism, leg ulceration and possibly stroke, is an important contributor to death. This model can be used to compute a personalized measure of disease severity that might be useful for guiding therapeutic decisions and designing clinical trials.

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Combining Fetal Hemoglobin and Reticulocytosis to Index Clinical Severity of Sickle Cell Disease in Children.

Blood ◽

10.1182/blood.v114.22.2556.2556 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2556-2556

Author(s):

Emily Riehm Meier ◽

Colleen Byrnes ◽

Maxine Weissman ◽

Pierre Noel ◽

Naomi L.C. Luban ◽

...

Keyword(s):

Sickle Cell Disease ◽

Supportive Care ◽

Disease Severity ◽

Sickle Cell ◽

Fetal Hemoglobin ◽

Treatment Decisions ◽

Clinical Severity ◽

Acute Chest Syndrome ◽

Cell Disease ◽

F Cells

Abstract Abstract 2556 Poster Board II-533 Predictors of disease severity during infancy or childhood in patients with sickle cell disease (SCD) are needed to guide treatment decisions with therapies that have known toxicities [transfusion, hydroxyurea (HU), bone marrow transplant]. Erythrocyte fetal hemoglobin (HbF) expression levels above 20% reduce sickle hemoglobin (HbS) polymerization and decrease hemolysis. As a result of the decreased hemolysis, the survival of erythrocytes is prolonged, and the overall level of erythropoiesis is reduced. To determine if clinical markers of increased HbF production and decreased erythropoiesis may be combined to score disease severity, we developed a Fetal Hemoglobin-Reticulocytosis Index (FRI) defined as: [HbF (%) × non-transfused F-cells (%)] / [Absolute Reticulocyte Count (K/uL)]. For these studies, red cell lysates were analyzed by high power liquid chromatography (HPLC) to estimate HbA, HbS, and HbF fractions. F-cells were analyzed by flow cytometry using antibodies directed against HbF, while transfused cells were labeled with antibodies directed against HbA. Dual staining with both antibodies provided a method for accurately distinguishing transfused and non-transfused F-cells (NT F-cells). A minimum of 10,000 cells was analyzed in all samples. Absolute reticulocyte counts (ARC) were determined using a Sysmex XE 2100 hematology analyzer (Sysmex America, Mundelein, IL). Preliminary studies revealed FRI values near 100 at one month of age followed by a rapid drop before the age of 4 years. Blood from children between the ages of 4 and 21 years was also studied to determine if FRI correlates with therapeutic regimen. FRI values for three groups were compared: those treated with chronic transfusion (n=19, mean FRI=0.72±1.04), HU (n=19, mean FRI=5.61±6.24), versus supportive care alone that did not include recent transfusions (n=42, mean FRI=2.70 ±4.85). When the FRI values from each of these groups were placed in rank order, the slope of the line increased sharply from a linear to an exponential shape near the FRI value of 2. To determine if the FRI=2 inflection may be indicative of reduced disease severity, the number of SCD events were determined in the 42 study subjects treated with supportive care. Overall, twenty-eight (66.7%) patients had an FRI<2, and fourteen (33.3%) patients had an FRI≥2. Among those patients, SCD events were tallied (listed in descending order according to number of events): painful crises requiring hospitalization (FRI<2, n=128; FRI≥2, n=25), pneumonia /acute chest syndrome (FRI<2, n=74; FRI≥2, n=18), splenic sequestration (FRI<2, n=14; FRI≥2, n=0), conditional transcranial Doppler [(TCD), FRI<2, n=13; FRI≥2, n=1), silent stroke (FRI<2, n=4; FRI≥2, n=2), bacteremia (FRI<2, n=2; FRI≥2, n=1), cholecystectomy (FRI<2, n=3; FRI≥2, n=0), and nephropathy (FRI<2, n=1; FRI≥2, n=0). None of the supportive care group had an overt stroke, abnormal TCD, sickle cell retinopathy, or priapism. Age adjusted analysis showed that the FRI≥2 group had significantly fewer total events per year [events/year: FRI<2 (0.70±0.52) vs. FRI≥2 (0.38 ± 0.36), p=0.02]. These data suggest that combining the clinical parameters of fetal hemoglobin production and reticulocytosis provides a simple index for SCD severity. Based upon this retrospective data, prospective studies are underway to determine if the FRI decline during infancy or FRI levels in childhood are useful to predict clinical severity and treatment decisions in SCD patients. Disclosures: No relevant conflicts of interest to declare.

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