Impact of a paediatric-adult care transition programme on the health status of patients with sickle cell disease: study protocol for a randomised controlled trial (the DREPADO trial)

BACKGROUND

Thanks to advancements in medical care, a majority of patients with sickle cell disease (SCD) worldwide live beyond 18 years of age, and therefore, patients initially followed in paediatric departments are then transferred to adult departments. This paediatric-adult care transition is a period with an increased risk of discontinuity of care and subsequent morbidity and mortality. During this period, the patient will have to manage new interlocutors and places of care, and personal issues related to the period of adolescence. To take into consideration all these aspects, an interesting approach is to use the whole system approach to the patient, as presented in the biopsychosocial approach. The aim of this trial is to evaluate the impact of the proposed biopsychosocial paediatric-adult transition programme.

METHODS

The DREPADO study is a multicentre randomised control trial comparing a control group (Arm A) to an interventional group with a paediatric-adult transition programme based on a biopsychosocial approach (Arm B). To be included, patients should have the SS, SC, or Sβ form of sickle cell disease and be aged between 16 and 17 years. The randomisation in a 1:1 ratio assigns to Arm A or B. The primary outcome is the number of hospital admissions and emergencies for complications in the index hospital, in the 2 years after the first consultation in the adult department of care. Secondary outcomes consider the quality of life, but also include coping skills such as sense of self-efficacy and disease knowledge. To provide patient and parent knowledge and coping skills, the transition programme is composed of three axes: educational, psychological, and social, conducted individually and in groups.

DISCUSSION

By providing self-care knowledge and coping skills related to SCD and therapeutics, helping empower patientsin relation to pain management and emotions, and facilitating the relationship to oneself, others, and care in Arm B of the DREPADO study, we believe that the morbidity and mortality of patients with SCD may be reduced after the proposed paediatric-adult transition programme.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT03786549; registered on 17 December 2018; https://clinicaltrials.gov/.

The impact of sickle cell disease on oral health-related quality of life

PURPOSE

The purpose of this study was to characterize the impact of sickle cell disease (SCD) on oral health and examine its impact on quality of life.

METHODS

Fifty-four study subjects were recruited from the sickle cell clinic and 52 control subjects from the adolescent medicine clinic at Nationwide Children's Hospital, Columbus, Ohio. A dental exam was performed to determine each participant's caries burden. The Child Oral Health Impact Profile survey was used to assess their oral health-related quality of life (OHRQoL).

RESULTS

Most subjects in both the SCD and control groups rated their overall health and oral health as "good" or "excellent." There was no statistically significant difference in OHRQoL between these groups. Additionally, no significant relationship was found between white blood cell count, medication intake, or the number of sickle cell crises as related to the caries burden. Statistically significant differences were detected in caries burden between the control group and the sickle cell hemoglobin C disease (HbSC) group (P<.02) and between the sickle cell anemia and HbSC subjects (P=.04).

CONCLUSIONS

Adolescents with sickle cell hemoglobin C disease had fewer caries than peers with sickle cell anemia or controls, though the cause of this finding is not clear.

Hemorheological alterations, decreased cerebral microvascular oxygenation and cerebral vasomotion compensation in sickle cell patients

Sickle cell anemia (SS) is characterized by a reduced cerebral microvascular oxygen saturation (cerebral TOI), which is not associated with hemoglobin concentration. Cerebral TOI has never been studied in sickle cell-hemoglobin C disease (SC). We focused on the relationships between hemorheological alterations and cerebral TOI in sickle cell patients with no cerebral vasculopathy and on the usefulness of TOI variability to assess the cerebral vasomotion activity. The blood rheological profile, the level of cerebral TOI (spatial resolved spectroscopy) and the cerebral TOI variability, which reflects vasomotion activity, were compared between 20 healthy subjects (AA), 21 SC patients, and 21 SS patients. Cerebral TOI exhibited the following order: AA > SC > SS. The low cerebral TOI in SS patients was related to red blood cell aggregation and deformability properties. The cerebral TOI variability of SS and SC patients was increased above healthy values and vasomotion activity was negatively associated with the reduced cerebral TOI in SS patients. We demonstrated that (1) blood rheology could be involved in the reduced cerebral TOI in SS patients but not in SC patients; (2) vasomotion activity is increased in SS and SC patients to compensate for the reduced cerebral TOI.

Opioid patient controlled analgesia use during the initial experience with the IMPROVE PCA trial: a phase III analgesic trial for hospitalized sickle cell patients with painful episodes

Opioid analgesics administered by patient-controlled analgesia (PCA)are frequently used for pain relief in children and adults with sickle cell disease (SCD) hospitalized for persistent vaso-occlusive pain, but optimum opioid dosing is not known. To better define PCA dosing recommendations,a multi-center phase III clinical trial was conducted comparing two alternative opioid PCA dosing strategies (HDLI—higher demand dose with low constant infusion or LDHI—lower demand dose and higher constant infusion) in 38 subjects who completed randomization prior to trial closure. Total opioid utilization (morphine equivalents,mg/kg) in 22 adults was 11.6 ± 2.6 and 4.7 ± 0.9 in the HDLI andin the LDHI arms, respectively, and in 12 children it was 3.7 ± 1.0 and 5.8 ± 2.2, respectively. Opioid-related symptoms were mild and similar in both PCA arms (mean daily opioid symptom intensity score: HDLI0.9 ± 0.1, LDHI 0.9 ± 0.2). The slow enrollment and early study termination limited conclusions regarding superiority of either treatment regimen. This study adds to our understanding of opioid PCA usage in SCD. Future clinical trial protocol designs for opioid PCA may need to consider potential differences between adults and children in PCA usage.

Results from transcranial Doppler examination on children and adolescents with sickle cell disease and correlation between the time-averaged maximum mean velocity and hematological characteristics: a cross-sectional analytical study

CONTEXT AND OBJECTIVE

Transcranial Doppler (TCD) detects stroke risk among children with sickle cell anemia (SCA). Our aim was to evaluate TCD findings in patients with different sickle cell disease (SCD) genotypes and correlate the time-averaged maximum mean (TAMM) velocity with hematological characteristics.

DESIGN AND SETTING

Cross-sectional analytical study in the Pediatric Hematology sector, Universidade Federal de São Paulo.

METHODS

85 SCD patients of both sexes, aged 2-18 years, were evaluated, divided into: group I (62 patients with SCA/Sß(0) thalassemia); and group II (23 patients with SC hemoglobinopathy/Sß(+) thalassemia). TCD was performed and reviewed by a single investigator using Doppler ultrasonography with a 2 MHz transducer, in accordance with the Stroke Prevention Trial in Sickle Cell Anemia (STOP) protocol. The hematological parameters evaluated were: hematocrit, hemoglobin, reticulocytes, leukocytes, platelets and fetal hemoglobin. Univariate analysis was performed and Pearson's coefficient was calculated for hematological parameters and TAMM velocities (P < 0.05).

RESULTS

TAMM velocities were 137 ± 28 and 103 ± 19 cm/s in groups I and II, respectively, and correlated negatively with hematocrit and hemoglobin in group I. There was one abnormal result (1.6%) and five conditional results (8.1%) in group I. All results were normal in group II. Middle cerebral arteries were the only vessels affected.

CONCLUSION

There was a low prevalence of abnormal Doppler results in patients with sickle-cell disease. Time-average maximum mean velocity was significantly different between the genotypes and correlated with hematological characteristics.

Anomalous renal effects of tin protoporphyrin in a murine model of sickle cell disease

In human and murine models of sickle cell disease (SCD), heme oxygenase-1 (HO-1) is induced in the kidney, an organ commonly involved in SCD. The present study assessed the role of HO-1 by using a competitive inhibitor of HO activity, tin protoporphyrin (SnPP), in protocols affording a composite, clinically relevant analysis of the kidney in SCD under unstressed and stressed conditions. Whereas short-term administration of SnPP exerted comparable renal hemodynamic effects in wild-type and sickle mice, chronic administration of SnPP exerted divergent effects: SnPP provoked tubulointerstitial inflammation and up-regulation of injury-related genes in wild-type mice, whereas in sickle mice SnPP reduced expression of injury-related genes and vascular congestion without provoking tubulointerstitial inflammation. SnPP also protected against the heightened sensitivity to renal ischemia observed in sickle mice, preventing ischemia-induced worsening of renal injury in sickle mice above that observed in wild-type mice. Effective and comparable inhibition of HO activity by SnPP in wild-type and sickle mice was confirmed. These findings suggest that induction of HO-1, at least as assessed by this approach, may contribute to renal injury in this murine model of SCD and uncover an experimental maneuver that protects the kidney in murine SCD.

Insights into elevated distortion product otoacoustic emissions in sickle cell disease: Comparisons of hydroxyurea-treated and non-treated young children

Distortion product otoacoustic emissions (DPOAEs) were examined in 15 normal-hearing African-American children between the ages of 6 and 14 years with homozygous sickle cell disease (SCD), who were on a regimen of hydroxyurea (HDU), a drug that reduces inflammatory processes and symptoms of SCD; a matched group of 15 African-American children with homozygous SCD not on HDU; and 15 African-American children with normal hemoglobin. DPOAEs were evoked by 13 primary tone pairs with f2 frequencies ranging from 1000 to 4500 Hz. Increased DPOAE amplitudes, believed to be a precursor of eventual hearing loss, were evident in children with SCD who were not receiving HDU. Those taking HDU had DPOAE amplitudes similar to normal controls. These findings suggest that HDU, in addition to reducing symptoms of SCD, may play a role in inhibiting or preventing cochlear pathology and hearing loss in individuals with SCD.

Incidence and natural history of proliferative sickle cell retinopathy: observations from a cohort study

OBJECTIVE

To describe the incidence, prevalence, and natural history of proliferative sickle cell retinopathy (PSR).

DESIGN

Prospective longitudinal study over 20 years.

PARTICIPANTS

Newborn screening of 100000 consecutive deliveries from 1973 to 1981 identified 315 children with homozygous sickle cell (SS) disease and 201 with SS-hemoglobin C (SC) disease. By the age of 5 years, 307 SS patients and 166 SC patients were alive and living in Jamaica and were recruited for this ophthalmic study.

METHODS

Description of retinal vascular changes on annual angiography and angioscopy.

MAIN OUTCOME MEASURES

Incidence and prevalence of PSR and its behavior on follow-up. Progression of PSR was investigated using the number of eyes affected (none, one, both) and the interval until PSR onset.

RESULTS

At last review in January 2000, PSR had developed in 59 patients (14 SS, 45 SC), unilaterally in 36 patients and bilaterally in 23. Incidence increased with age in both genotypes, with crude annual incidence rates of 0.5 cases (95% confidence interval [CI], 0.3-0.8) per 100 SS subjects and 2.5 cases (95% CI, 1.9-3.3) per 100 SC subjects. Prevalence was greater in SC disease, and by the ages of 24 to 26 years, PSR had occurred in 43% subjects with SC disease and in 14% subjects with SS disease. Patients with unilateral PSR had a 16% (11% SS, 17% SC) probability of regressing to no PSR and a 14% (16% SS, 13% SC) probability of progressing to bilateral PSR. Those with bilateral PSR had an 8% (8% SS, 8% SC) probability of regressing to unilateral PSR and a 1% (0 SS, 2% SC) probability of regressing to a PSR-free state. Irretrievable visual loss occurred in only 1 of 82 PSR-affected eyes, and 1 required detachment surgery and recovered normal visual acuity.

CONCLUSIONS

Longitudinal observations over 20 years in a cohort of patients followed from birth confirms a greater incidence and severity of PSR in SC disease, and shows that spontaneous regression occurred in 32% of PSR-affected eyes. Permanent visual loss was uncommon in subjects observed up to the age of 26 years.

Acute myocardial infarction in hemoglobin SC disease

Although there are reports of myocardial infarction (MI) in patients with sickle cell diseases, an antemortem diagnosis of acute MI in a patient with compound heterozygous hemoglobin SC disease has not been reported. Herein, we present a patient with hemoglobin SC who suffered an acute MI. She had typical chest pain for myocardial ischemia, associated with ST elevations on the electrocardiogram (EKG) and elevations of cardiac injury markers diagnostic of infarction. The patient was treated with conventional therapies for acute coronary syndrome and also emergent red blood cell exchange. Interestingly, coronary angiography was completely normal in this patient. Potential mechanisms and management for acute MI in patients with sickle cell disease are discussed.

The paradox of hemoglobin SC disease

Homozygous HbC gene results only in mild hemolytic anemia. In HbSC disease red cells contain equal levels of HbS and HbC. It is a paradox that HbSC exhibit a moderately severe phenotype in spite of being a mixture of HbS trait and HbC trait, neither of which has significant pathology. Why does the combination of these two Hbs result in a serious disease? The short answer is that HbC enhances, by dehydrating the SC red cell, the pathogenic properties of HbS, resulting in a clinically significant disorder, but somewhat milder that sickle cell anemia (SCA). Nevertheless, retinnitis proliferans, osteonecrosis, and acute chest syndrome have equal or higher incidence in HbSC disease compared to SCA. This pathogenic trick is accomplished by HbC inducing, by mechanisms not fully understood, an increase in the activity of K:Cl cotransport that induces the lost of K(+) and consequently of intracellular water. This event creates a sufficient increase of MCHC, so that the lower levels of HbS found in SC red cells can polymerize rapidly and effectively. This situation offers a unique opportunity: if we could inhibit the effect of HbC on K(+) transport we can cure the disease.

Role of phlebotomy in the management of hemoglobin SC disease: case report and review of the literature

Marked variability is a keynote in the disease course of patients with hemoglobin SC (Hb SC) and hemoglobin S/beta(+)-thalassemia (Hb S/beta(+)-thal), with some patients having a frequency of complications and painful episodes similar to patients with homozygous sickle cell (Hb SS) disease. One possible explanation is that the higher hematocrit in these syndromes may contribute to an increase in blood viscosity, leading to vaso-occlusive pain episodes as well as an increased incidence of thromboembolic complications and retinopathy. We present a patient with Hb SC disease with an excellent baseline functional status who developed splenic infarction at a high altitude. Following splenectomy, the patient developed a sustained increase in hematocrit, an increase in the frequency of painful episodes, as well as new-onset dizziness and malaise. We initiated a therapeutic phlebotomy program in order to lower the hematocrit to pre-splenectomy values, as well as to induce iron deficiency. Repeated phlebotomy resulted in a dramatic decrease in symptoms. Our patient no longer requires narcotic analgesics for pain, has resolution of constitutional symptoms, and has not required further hospitalizations for vaso-occlusive pain crises. The correlation between symptoms and hematocrit levels supports the importance of blood viscosity in contributing to this patient's symptoms. A trial of phlebotomy to reduce viscosity in patients with higher hematocrit values should be considered as an intervention for symptomatic patients with sickle cell disease.

A human embryonic hemoglobin inhibits Hb S polymerization in vitro and restores a normal phenotype to mouse models of sickle cell disease

The principle that developmentally silenced globin genes can be reactivated in adults with defects in beta-globin gene expression has been well established both in vitro and in vivo. In practice, levels of developmental stage-discordant fetal gamma globin that can be achieved by using currently approved therapies are generally insufficient to fully resolve typical clincopathological features of sickle cell disease. The therapeutic potential of another developmentally silenced globin--embryonic epsilon globin--has been difficult to evaluate in the absence of a convenient expression system or an appropriate experimental model. The current work analyzes the antisickling properties of an epsilon -globin-containing heterotetramer (Hb Gower-2) both in vitro as well as in vivo in a well-established mouse model of sickle cell anemia. These animals, expressing 100% human Hb S, display a chronic hemolytic anemia with compensatory marrow and extramedullary erythropoiesis, abundant circulating sickled erythrocytes, and chronic tissue damage evidenced by parallel histopathological and functional deficits. By comparison, related mice that coexpress Hb S as well as Hb Gower-2 exhibit normal physiological, morphological, histological, and functional attributes. Subsequent in vitro analyses substantiate results from whole-animal studies, indicating that the polymerization of deoxygenated Hb S can be significantly slowed by relatively small quantities of Hb Gower-2. Together, the in vivo and in vitro analyses suggest that reactivation of epsilon-globin gene expression would be therapeutically beneficial to adults with sickle phenotypes, and provide a rationale for detailed investigations into the molecular basis for its developmental silencing.

Sickle cell disease and age at menarche in Jamaican girls: observations from a cohort study

AIMS

(1) To investigate the distribution of age at menarche in a representative sample of 99 patients with homozygous sickle cell (SS) disease, 69 with sickle cell haemoglobin C (SC) disease, and 100 controls with a normal haemoglobin (AA) genotype followed in a cohort study from birth. (2) To explore the determinants of the age at menarche.

METHODS

Children ascertained in a newborn screening programme were followed prospectively from birth to age 18-26.5 years with regular assessments of height, weight, pubertal stage, and haematological indices at the Sickle Cell Clinic of the University Hospital of the West Indies.

RESULTS

All subjects have now reached menarche and the mean age in normal controls (13.0 years) was significantly earlier than in SC disease (13.5 years) or SS disease (15.4 years). Greater weight and earlier age at menarche was the only association significant across all genotypes although additional contributions occurred from fetal haemoglobin and red cell count in SS disease. Alpha thalassaemia, which ameliorates many of the effects of SS disease, had no discernible effect on menarche.

CONCLUSIONS

Mean age at menarche is delayed by 0.5 years in SC disease and by 2.4 years in SS disease. Weight appears to be the principle determinant of age at menarche.

Oral citrulline as arginine precursor may be beneficial in sickle cell disease: early phase two results

L-Arginine may be a conditionally essential amino acid in children and adolescents with sickle cell disease, particularly as required substrate in the arginine-nitric oxide pathway for endogenous nitrovasodilation and vasoprotection. Vasoprotection by arginine is mediated partly by nitric oxide-induced inhibition of endothelial damage and inhibition of adhesion and activation of leukocytes. Activated leukocytes may trigger many of the complications, including vasoocclusive events and intimal hyperplasias. High blood leukocyte counts during steady states in the absence of infection are significant laboratory risk factors for adverse complications. L-Citrulline as precursor amino acid was given orally twice daily in daily doses of approximately 0.1 g/kg in a pilot Phase II clinical trial during steady states in four homozygous sickle cell disease subjects and one sickle cell-hemoglobin C disease patient (ages 10-18). There soon resulted dramatic improvements in symptoms of well-being, raised plasma arginine levels, and reductions in high total leukocyte and high segmented neutrophil counts toward or to within normal limits. Continued L-citrulline supplementation in compliant subjects continued to lessen symptomatology, to maintain plasma arginine concentrations greater than control levels, and to maintain nearly normal total leukocyte and neutrophil counts. Side effects or toxicity from citrulline were not experienced. Oral L-citrulline may portend very useful for palliative therapy in sickle cell disease. Placebo-controlled, long-term trials are now indicated.

Hemoglobin SC disease presenting as acute chest syndrome with ventilation-perfusion mismatches

Acute chest syndrome, characterized by fever, chest pain and pulmonary infiltrates, is a known complication of hemoglobin SC disease. A 41-year-old African male with previously unknown hemoglobinopathy developed an acute episode of fever, chest pain and dyspnea right after surgery for retinal detachment. The patient was suspected of having pulmonary thromboembolism. This was further suggested by a 'high probability' ventilation-perfusion scan. However, a pulmonary angiogram revealed no evidence of thromboembolism. Subsequently, the patient was recognized to have hemoglobin SC disease, with the acute chest syndrome. After appropriate treatment with antibiotics, hydration and exchange transfusion, the patient underwent another surgery without complications.

Language performance in three groups of children with sickle cell disease: those with stroke, without stroke, and at risk for stroke

Language performance was assessed in three groups of children (16 boys and 14 girls) with sickle cell disease: those with stroke, without stroke, and at risk for stroke. Scores of the three groups did not differ significantly on language comprehension, language expression, spatial orientation, or on overall combined performance scores. Such results have positive medical implications.

Maximum urine concentrating ability in children with Hb SC disease: effects of hydroxyurea

Studies in adults with Hb SC disease suggested that hydroxyurea reduced hemolysis and increased red cell hydration. Because increased hydration should diminish the polymerization tendency of Hb S we hypothesized that hydroxyurea might repair the urine concentration defect of HbSC disease. Eight Hb SC disease patients, aged 10 to 17 years, were given hydroxyurea daily. Maximal urine concentrating ability following overnight fasting and after subcutaneous arginine vasopressin (dDAVP), blood counts, and cell volumes were observed for 12-15 months. All patients had impaired urine concentrating ability prior to hydroxyurea treatment and failed to increase their ability to concentrate urine following treatment (maximum urine concentration after an overnight fast and dDAVP, 520-530 mOsm). Mean corpuscular volume (MCV) and reticulocyte MCV increased after administration of hydroxyurea, and the reticulocyte count and ratio of red cell hemoglobin to reticulocyte hemoglobin fell but there was little change in PCV. Hb F increased substantially in 2 patients but showed little change in the remaining patients. There was no evidence that hydroxyurea was associated with increased urine concentrating ability in children with Hb SC disease. These results may reflect irreversible renal medullary damage prior to beginning treatment or insufficient intensity or duration of treatment.

Cardiorespiratory and metabolic responses to exercise in HbSC sickle cell patients

PURPOSE

Relative to healthy control individuals with normal hemoglobin (Hb), patients carrying the double heterozygous form of sickle cell disease (HbSC) display an impaired oxygen transport capacity. The present study was undertaken to determine the influence of the decreased oxygen availability associated with the presence of HbSC on the cardiorespiratory and metabolic responses to endurance exercise.

METHODS

Eleven black men affected by the double heterozygous form of the sickle cell disease (HbSC group) and seven healthy subjects with normal Hb (HbAA group) of the same ethnic origin submitted successively to an incremental exercise test to exhaustion on a cycle ergometer for the determination of their maximal tolerated power and to a 20-min endurance exercise.

RESULTS

The HbSC had a significantly lower exercise tolerance than the HbAA. During the endurance exercise, they exhibited furthermore significantly lower VO2, VCO2, and minute ventilation V(E) than the HbAA. Despite the fact that the HbSC exercised at a significantly lower mean absolute work rate than the HbAA, except for the ventilatory equivalent for CO2 (V(E)/VCO2), which was higher (P < 0.001) in the HbSC group, the other parameters recorded during the 20-min endurance exercise (heart rate, arterial PaO2, PaCO2, pH, lactate, and VE/VO2, the ventilatory equivalent for O2) and during the subsequent recovery (blood lactate) were similar for both groups.

CONCLUSION

The study underscores the importance of considering relative work rate as well as absolute work rate to arrive at a correct interpretation of exercise and recovery data. The results give evidence that the modifications of homeostasis brought into play by exercise were shifted toward distinctly lower absolute work rates in HbSC patients.

Major changes in sickle cell disease

Clinical, molecular, and genetic advances have revealed new pathophysiologic insights and treatments for the growing number of recognized hematologic and nonhematologic abnormalities in sickle cell disease. Treatment targets of cellular dehydration, sickle hemoglobin concentrations, endothelial dysfunction, and abnormal coagulation regulation have been validated as potential therapy. New uses for transfusion therapy hold the promise of decreased major symptoms of acute chest syndrome, stroke, and severe pain crises, but at the expense of increased risk for transfusion reactions, infections, and iron overload. Accumulated experience with autologous, chimeric, and stem cell bone marrow transplantation holds promise for a small percentage of patients with disease. Patient selection, suitable donors, and early mortality are still limiting factors. Genetic manipulation, which offers hope for ameliorating the disease in a larger percentage of patients, is progressing slowly. Combination and staged therapies will be developed and matched to the severity and progression of the patient's disease. Strategies for prevention of major organ damage to the brain, heart, lungs, and kidneys will be prospectively evaluated and refined.

Platelet-erythrocyte adhesion in sickle cell disease

BACKGROUND

The abnormal adherence of sickle red blood cells (sRBC) to other cell types likely contributes to vaso-occlusion. Increased numbers of platelet-erythrocyte aggregates (PEA) and platelet activation have been described in sickle cell disease. The present study was undertaken to determine the contribution, if any, of the extracellular matrix protein thrombospondin to the adhesion of sRBC and platelets.

METHODS

Platelet activation and PEA were measured using fluorescent-labeled monoclonal antibodies and flow cytometry. Platelet red-cell adhesion was measured by a gravity sedimentation assay. Erythrocyte-bound thrombospondin (TSP) was determined by enzyme-linked immunoabsorbant assay (ELISA).

RESULTS

Our studies demonstrate significant platelet activation and adhesion of sRBC to platelets in sickle cell disease. Thrombospondin was detected on sRBC. There was variable inhibition of sRBC-platelet adhesion by antibodies to CD36 (thrombospondin receptor) and antibodies to thrombospondin.

CONCLUSIONS

Thrombospondin on sRBC may mediate, at least in part, sRBC-platelet adhesion in sickle cell disease. The study of heterotypic cell-cell interactions is important in understanding the pathogenesis of vaso-occlusion in sickle cell disease.

Growth hormone secretion and circulating insulin-like growth factor-I (IGF-I) and IGF binding protein-3 concentrations in children with sickle cell disease

Impaired growth involving both height and weight accompanying sickle cell disease (SCD) poses diagnostic and therapeutic problems. We undertook this study to test the hypothesis that this impaired growth is associated with abnormalities of the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGF binding protein-3 (IGFBP-3) axis in 21 children with SCD and that SCD is associated with GH resistance. Nine of 21 children with SCD had a defective GH response to both clonidine and glucagon provocation (peak < 10 micrograms/L); these children differed from the 12 others in having slower linear growth velocity (GV and GVSDS), lower circulating concentrations of IGF-I and IGFBP-3, and either partial or complete empty sellae in computed tomographic scans of the hypothalamic-pituitary area. In this group of patients with SCD, it appears that defective GH secretion and consequent low IGF-I production are the major etiological factors causing the slow growth. The two groups with SCD did not differ significantly in dietary intake, body mass index (BMI), midarm circumferences, skinfold thickness, serum albumin concentration, or intestinal absorption of D-xylose. A single injection of GH produced a smaller increase in circulating IGF-I in children with SCD with or without defective GH secretion versus 10 age-matched children with idiopathic short stature (ISS) and 11 children with isolated GH deficiency (GHD), suggesting partial GH resistance in the SCD group. The presence of defective GH secretion, decreased IGF-I synthesis, and partial resistance to GH in short children with SCD suggests that treatment with IGF-I may be superior to GH therapy for improving growth.

Lung function in infants with sickle cell disease

We performed pulmonary function testing in 20 infants (11 male and 9 female; ages 3-30 months) with sickle cell disease to assess whether abnormal lung function develops early in life. Respiratory system compliance (Crs) and resistance (Rrs) were measured by the passive occlusion technique, functional residual capacity (FRC) was measured by the nitrogen washout technique, and tidal flow-volume loops and partial expiratory flow-volume curves were obtained by the thoracoabdominal compression technique to detect airway obstruction. Patients with Hb SS (Group I, n = 12) had significantly lower hemoglobin levels and a higher (but not significant) incidence of acute chest syndrome (ACS), vasoocclusive crisis (VOC), splenic sequestration, transfusions, and history of intermittent bronchospasm compared to with patients with hemoglobinopathies Hb SC, Hb Sbt and Hb SF (Group II; n = 8). Both groups had elevated FRC, decreased maximum expiratory flows at FRC (V'max,FRC), and decreased time needed to reach peak expiratory flow (tme/tE), suggesting lower airway obstruction (LAO) and hyperinflation. Restrictive disease was found in only three patients of Group I. Our findings suggest that in sickle cell disease (especially among patients with Hb SS), abnormal lung function (predominantly LAO) may be present in early infancy. Airway reactivity may play a role in the pathogenesis, but the relation to VOC or ACS remains unclear.

Natural history of blood pressure in sickle cell disease: risks for stroke and death associated with relative hypertension in sickle cell anemia

PURPOSE

Blood pressure in individuals who have sickle cell disease has been reported to be lower than published normal values. We determine whether and to what degree this is true, using data obtained as part of a large natural history study.

PATIENTS AND METHODS

Blood pressure was measured annually for 3,317 subjects with sickle cell disease who were 2 years old or older. Values obtained were compared with those reported by the National Health and Nutrition Examination Survey I and II (NHANES I and II). They were further analyzed with respect to age, sex, height, weight, hematologic diagnosis, blood urea nitrogen and creatinine, stroke, and death.

RESULTS

Blood pressure was significantly lower in subjects with sickle cell anemia than published norms for age, race, and sex, a difference that increased with age. It correlated with body mass index, hemoglobin, measures of renal function and age, but the strength of the correlation varied among age and sex subgroups. The risk for occlusive stroke increased with systolic but not diastolic pressure. Mortality was related to elevated blood pressure in males (P < 0.05) and to a lesser extent in females (P = 0.10). In subjects with hemoglobin SC disease, blood pressure also deviated from normal but to a lesser degree.

CONCLUSION

Blood pressure is generally lower than normal in individuals with sickle cell anemia. Those with high values relative to this population had an increased risk of stroke and death. Blood pressure should be monitored but values obtained must be assessed relative to the lower values expected for patients with this disease. Those with blood pressure values above 140/90 mm Hg should be evaluated and considered for treatment.

Headache and scalp edema in sickle cell disease

BACKGROUND

Major neurological complications of sickle cell disease include cerebral infarction and intracranial hemorrhages.

METHODS

We describe the case of a 25-year-old man with sickle cell disease who developed a severe headache of acute onset, located at the vertex. There was associated pitting edema of the scalp.

RESULTS

Technetium and gallium bone imaging showed focal decreased uptake of the tracers, consistent with a recent fronto-parietal skull infarction. Management included intravenous hydration and analgesic medication.

CONCLUSIONS

In addition to the more common intracranail vaso-occlusive complications, skull infarction should be considered as a cause of newonset headache in patients with sickle cell disease, especially if scalp edema is present.

A simple splenic reticuloendothelial function test: counting erythrocytes with argyrophilic inclusions

The presently accepted methods for evaluation of splenic reticuloendothelial (RE) function include 99mTc sulfur colloid spleen scan, antibody-coated autologous erythrocyte clearance, and pocked erythrocyte count. All methods involve special equipment and/or risk and inconvenience to patients. A simple method of assessing splenic RE function was developed by counting erythrocytes with argyrophilic inclusions using a simple silver stain and an ordinary microscope. To test the validity of this method, blood samples were collected from patients suspected of having hyposplenia or asplenia, including patients with history of splenectomy, sickle cell disease or trait, and newborns. Blood samples were also collected from normal adults and from patients without hyposplenia or asplenia as controls. The samples were tested by this method and compared to the pocked erythrocyte count that served as a gold standard. The results obtained by the two methods were found to be very comparable with little overlap between those from controls and patients with definite hyposplenia or asplenia. With the pocked erythrocyte count as the gold standard, this method has a sensitivity of 88.9% and a specificity of 97.1%. However, this method requires no special equipment. Staining can be applied to fresh blood smears as well as to Wright-stained smears, and the silver-stained smears are permanent.

Disturbance of plasma and platelet thrombospondin levels in sickle cell disease

Thrombospondin (TSP), a large protein found in platelet alpha-granules (as TSP-1), mediates adhesion of sickle reticulocytes to cultured vascular endothelium. To further explore the physiologic relevance of this observation, we have measured plasma TSP levels and platelet TSP-1 content in subjects with sickle cell disease. Plasma TSP levels were similar for normal controls (mean 491 ng/ml, range 331-723) and steady-state HbSS patients (mean 536, range 333-1107) and were significantly (P = 0.012) but variably elevated for HbSS patients presenting with acute painful crisis (mean 868, range 442-2780). Some of these elevated plasma TSP levels reached those previously observed to support maximal red cell adhesion to endothelium in vitro. Compared to normals, both steady-state and in-crisis HbSS patients had significantly (P < 0.001) depressed platelet TSP-1 content (82.6 +/- 11.9, 47.1 +/- 16.0 and 45.9 +/- 20.7 ng/l0(6) platelets, respectively, mean +/- SD). HbSC disease patients, all examined during steady state, had low-normal plasma levels of TSP and either normal or depressed platelet TSP-1 content. Serial observations on three sickle cell anemia subjects indicated a probable relationship between platelet TSP-1 release, elevated plasma TSP levels, and acute vaso-occlusive episodes. These results suggest a state of ongoing release and depletion of TSP-1 from activated platelets in patients with sickle cell disease.

Stroke in children and young adults

This selective review of stroke in children and young adults addresses: (1) stroke in sickle cell disease, particularly the prognostic use of transcranial Doppler, (2) oral contraceptives as a stroke risk factor, (3) stroke in pregnancy, and (4) the prognosis of ischemic stroke in young adults. Factors relevant to the primary prevention and outcome of stroke are emphasized.

Daily variability in resting levels of cardiovascular variables in normal subjects and those with homozygous sickle cell disease

Measurements were made of cardiovascular variables and oral temperature in 16 male subjects with homozygous sickle cell disease (SS) and in 17 matched controls (AA) at 10.00 a.m., 1.00 p.m. and 4.00 p.m. All subjects were in a rested state throughout. At 10.00 a.m., mean arterial pressure was lower, while heart rate, total forearm blood flow and cutaneous red cell flux in the forearm were higher in SS than AA. Vascular resistance in total forearm and forearm skin, calculated by dividing arterial pressure by blood flow or red cell flux, were lower in SS but hand cutaneous red cell flux and vascular resistance were not significantly different in SS and AA. In both SS and AA, there were parallel increases over the three sessions, in mean arterial pressure (by approximately 12 and 10%, respectively) forearm vascular resistance (by approximately 17 and 27%) and hand cutaneous vascular resistance and hand cutaneous resistance (by approximately 2240 and 350%) whereas forearm blood flow and hand cutaneous red cell flux fell. By contrast, forearm cutaneous resistance showed no change during the day in SS, but increased progressively in AA (by approximately 75%). These results indicate that, during the day, there is progressive vasoconstriction in forearm muscle and hand skin in SS and AA and also in forearm skin of AA that contributes to a progressive rise in the resting level of mean arterial pressure. We suggest this daily variability should be considered in studies of cardiovascular function: within a given study they should be performed at the same time of day.

Functional asplenia in hemoglobin SC disease

The incidence of functional asplenia in sickle-hemoglobin C (SC) disease has not been defined, and the use of prophylactic penicillin to prevent life-threatening septicemia in this disorder is controversial. The percentage of red blood cells with pits (pit count) is a reliable assay of splenic function in other disorders but has not been validated in hemoglobin SC disease. To address these issues, we conducted a prospective, multicenter study of splenic function in persons with hemoglobin SC disease. Baseline clinical data were recorded, and red blood cell pit counts were performed on 201 subjects, aged 6 months to 90 years, with hemoglobin SC; 43 subjects underwent radionuclide liver-spleen scanning. Pit counts greater than 20% were associated with functional asplenia as assessed by liver-spleen scan, whereas pit counts less than 20% were found in subjects with preserved splenic function. Pit counts greater than 20% were present in 0 of 59 subjects (0%) less than 4 years of age, in 19 of 86 subjects (22%) 4 to 12 years of age, and in 25 of 56 subjects (45%) greater than 12 years of age. Other subjects with hemoglobin SC, who had previously undergone surgical splenectomy, had higher pit counts (59.7% +/- 9.5%) than splenectomized subjects without hemoglobinopathy (38.5% +/- 8.8%) or with sickle cell anemia (20.5% +/- 1.9%; P < .001). Two subjects with hemoglobin SC disease (not splenectomized), ages 14 and 15 years, with pit counts of 40.3% and 41.7% died from pneumococcal septicemia. These data indicate that functional asplenia occurs in many patients with hemoglobin SC disease, but its development is usually delayed until after 4 years of age. The pit count is a reliable measure of splenic function in hemoglobin SC disease, but values indicative of functional asplenia (> 20% in our laboratory) are higher than in other disorders. The routine administration of prophylactic penicillin to infants and young children with hemoglobin SC disease may not be necessary.

Delayed adolescent growth in homozygous sickle cell disease

Analysis of the growth abnormalities in sickle cell disease has been limited by the lack of longitudinal observations in individuals, and by an inability to quantitate the observed patterns. To investigate the timing and pattern of the adolescent growth spurt, longitudinal observations of height from the Jamaican cohort study were fitted to a mathematical model of growth (Preece-Baines model 1). The study included 44 children with homozygous sickle cell (SS) disease, 44 age and sex matched subjects with sickle cell haemoglobin C (SC) disease, and 44 age and sex matched controls with normal (AA) haemoglobin. Compared with AA controls, the onset of the adolescent growth spurt was delayed in SS disease by 1.4 years (95% confidence interval 0.8 to 2.0) with no significant sex difference. The age at peak height velocity was delayed by 1.6 years (0.9 to 2.3) in SS compared with AA subjects but the adolescent growth of SS children was otherwise normal and there was no difference in the attained height by age 17.9 years. The growth spurt was not delayed in SC disease. The age at menarche in girls with SS disease (mean (SD) 15.4 (1.3) years) was significantly later than girls with SC disease (13.7 (1.7) years) and those with AA haemoglobin (13.1 (1.3) years) but these genotype differences were no longer significant after controlling for the delay in the adolescent growth spurt. The normally coordinated but slightly delayed pattern of growth and normal adult heights suggests a good prognosis for adolescent growth delay in SS disease. Most children with SS disease can therefore be reassured on the outcome of retarded adolescent growth.

Acute multiorgan failure syndrome: a potentially catastrophic complication of severe sickle cell pain episodes

The purpose of this report is to characterize the acute multiorgan failure syndrome that complicates some episodes of sickle pain. A retrospective chart review was used to identify episodes of sickle pain complicated by the acute failure of at least two of three organs: lung, liver, or kidney. The defining criteria of organ failure were established, and the clinical characteristics, laboratory values, treatment methods, and outcomes were noted in episodes that met the criteria. Seventeen episodes of acute multiorgan failure were identified in 14 patients, 10 with sickle cell anemia and 4 with hemoglobin SC disease. Most episodes occurred during a pain event that was unusually severe for the patient. The onset of organ failure was associated with fever, rapid fall in hemoglobin level and platelet count, nonfocal encephalopathy, and rhabdomyolysis. Bacterial cultures were negative in all but four episodes. Aggressive transfusion therapy was associated with survival and with rapid recovery of organ function in all but one episode. The syndrome developed in patients who had previously exhibited relatively mild disease with little evidence of chronic organ damage and relatively high hemoglobin values in steady state. Acute multiorgan failure syndrome is a severe, life-threatening complication of pain episodes in patients with otherwise mild sickle cell disease. The syndrome appears to be reversed with prompt, aggressive transfusion therapy. High baseline hemoglobin levels may represent a predisposing factor.

The shoulder in sickle-cell disease

Sickle-cell disease (SCD) is probably the commonest cause of avascular necrosis worldwide, and its prevalence appears to be rising in developed countries. Avascular necrosis of the humeral head is a common complication but has not been previously studied in detail. We have reviewed 138 patients with SCD for clinical, radiological and functional abnormalities of the shoulder, using a radiological classification designed for avascular necrosis of the shoulder. Radiographic lesions, frequently bilateral, were found in 28% and only 53% of patients had normal shoulder function. The management of this relatively common complication is difficult. Joint replacement is likely to fail and early diagnosis is important.

Adolescent blood pressure in a cohort study of sickle cell disease

BACKGROUND

Previous studies on low blood pressure in patients with homozygous sickle cell (SS) disease have sought new hypotheses on the mechanism of low blood pressure but have not analyzed the role of known determinants such as weight.

METHODS

Blood pressure has been measured by an automated oscillometric method in 220 patients with SS disease, 144 with sickle cell-hemoglobin C disease (both groups aged, 9.5 to 18.5 years) and 122 control subjects with a normal hemoglobin genotype (aged 16.0 to 18.5 years) participating in a cohort study from birth.

RESULTS

Significant age-related increases in systolic and mean arterial pressure occurred in sickle cell-hemoglobin C disease but not in SS disease. Further analyses were confined to a subgroup of 51 patients with SS, 41 patients with sickle cell-hemoglobin C, and 97 subjects with normal hemoglobin, aged 16.0 to 18.5 years in whom simultaneous measurements of height, weight, arm circumference, and hematologic test results were also available. Crude analyses showed significantly lower systolic, diastolic, and mean arterial pressure in SS disease compared with control subjects with normal hemoglobin, but further analysis showed the systolic difference to be confined to males and all differences disappeared after adjustment for weight. No differences occurred in sickle cell-hemoglobin C disease.

CONCLUSIONS

These results suggest that the lower blood pressure in SS disease is attributable to low weight and that no further mechanisms need be postulated.

Abnormalities of hemostasis in ischemic stroke

Despite important new diagnostic laboratory and imaging technologies, the cause of brain infarction remains unexplained in 20% to 40% of subjects. Most stroke patients do not require extensive evaluations of coagulation, but hypercoagulability may account for a significant proportion of unexplained strokes. Hemostatic abnormalities associated with stroke may be broadly classified as familial or acquired. Principal among the familial thrombotic coagulopathies are deficiencies in concentration or function in protein-C, protein-S, and antithrombin III, but other hereditary abnormalities include sickle cell disease, homocystinuria, and dysfibrinogenemia. The acquired disorders of hemostasis associated with stroke probably constitute a larger proportion of the important stroke-related coagulopathies. In particular, the aPL antibody syndrome is now strongly associated with thrombotic events including stroke, although neither the mechanism of thrombosis nor effective therapies for this syndrome have been clearly elucidated. Many of the acquired hemostatic abnormalities exist within a special clinical setting such as with malignancy or with myeloproliferative diseases, nephrotic syndrome, and liver disease. Presumably many of these share common pathways of coagulation activation or dysfunction with the inherited disorders. Most of the hemostatic disorders in stroke are associated with dysfunction of vascular endothelium and abnormalities of or interference with the natural anticoagulant proteins: protein-C, protein-S, and antithrombin III. Improved understanding of these relationships should lead to better diagnosis and treatment for people at risk of stroke.

Retinal vessel autoregulation in sickle cell patients

We tested retinal vessel autoregulation in 16 sickle cell patients and 6 controls by computer-assisted measurements of constriction of the superior and inferior temporal veins and arteries after pure oxygen breathing. Compared to the controls and corrected for age, we found a decrease of vasoconstriction in three of the four vessels measured in the sickle cell group, which was statistically significant only for the superior temporal artery (P 0.009). The number of patients was too small to allow a separate analysis of possible contributory factors within the sickle cell group, such as sickle cell hemoglobin subtype and extent of retinal ischemia. Our findings indicate a factor not yet well known in the pathophysiology of sickle cell disease: an abnormality of local microvascular control.

Case report: splenic infarction and acute splenic sequestration in adults with hemoglobin SC disease

While acute splenic sequestration and splenic infarction are commonly observed in infants and young children with sickle cell anemia, they are rarely experienced by adult hemoglobin S homozygotes because the recurrent splenic infarction that takes place during childhood is typically followed by scarring, atrophy, and splenic fibrosis. Both acute splenic sequestration and splenic infarction do remain relatively common in adults with the other sickle hemoglobinopathies. These episodes are almost certainly a consequence of the persistently enlarged and distensible spleens that often remain present in these conditions. In this report, the authors describe two adult patients with hemoglobin SC disease: one who developed acute splenic sequestration and one with splenic infarction. In neither case was there a history of recent air travel or exposure to altitude. The clinical course of these two syndromes is presented, and the hematologic, radiologic, and pathologic manifestations are discussed. Because they can sometimes be difficult to distinguish from one another, and because a failure to identify acute splenic sequestration can be catastrophic, these two entities must be included in the differential diagnosis for any hemoglobin SC patient who present with an unexplained fall in hemoglobin, left upper quadrant pain, unexplained fever, or symptomatic splenomegaly.

Spleen function in children with sickle B+ thalassemia

Splenic function in patients with sickle B+ (SB+) thalassemia has been poorly documented. We evaluated the clinical course and splenic function in 12 children with SB+ thalassemia with simultaneous technetium sulfur colloid spleen scans and determination of pitted erythrocytes by direct interference contrast microscopy (DICM). All patients displayed normal uptake of radiocolloid. Mean percentage of pitted erythrocytes was 2.2% compared to 0.06% in 10 normal eusplenic controls and 13.8% in 10 sickle cell patients. In this group of children, who were carefully monitored for 136 patient years, there was no episode of bacteremia/sepsis, and a low prevalence of vaso-occlusive episodes. The slight increase in percentage of pitted erythrocytes of SB+ thalassemia patients does not seem to herald any clinically relevant loss of splenic function. SB+ thalassemia children younger than 10 years of age who do not seem to present a higher risk of invasive bacterial infections than eusplenic children, should receive conservative treatment for isolated febrile episodes and should not be submitted to prophylactic penicillin.

Pain in sickle cell disease. Rates and risk factors

BACKGROUND AND METHODS

Acute episodes of pain are the principal symptom of sickle cell disease, but little is known about the epidemiologic features of these episodes or risk factors for them, nor is it known whether patients with high rates of such episodes die prematurely. We prospectively studied the natural history of sickle cell disease in 3578 patients ranging from newborns to persons up to 66 years old who were followed at clinical centers across the United States.

RESULTS

There were 12,290 episodes of pain in 18,356 patient-years. The average rate was 0.8 episode per patient-year in sickle cell anemia, 1.0 episode per patient-year in sickle beta 0-thalassemia, and 0.4 episode per patient-year in hemoglobin SC disease and sickle beta(+)-thalassemia. The rate varied widely within each of these four groups--e.g., 39 percent of patients with sickle cell anemia had no episodes of pain, and 1 percent had more than six episodes per year. The 5.2 percent of patients with 3 to 10 episodes per year had 32.9 percent of all episodes. Among patients with sickle cell anemia who were more than 20 years old, those with high rates of pain episodes tended to die earlier than those with low rates. High rates were associated with a high hematocrit and low fetal hemoglobin levels. alpha-Thalassemia had no effect on pain apart from its association with an increased hematocrit.

CONCLUSIONS

The "pain rate" (episodes per year) is a measure of clinical severity and correlates with early death in patients with sickle cell anemia over the age of 20. Even when the fetal hemoglobin level is low, one can predict that small increments in the level may have an ameliorating effect on the pain rate and may ultimately improve survival. This outcome is particularly encouraging to investigators studying hydroxyurea and other treatments designed to increase the fetal hemoglobin level.

Intravascular volume expansion and fetal outcome in pregnant Nigerians with hemoglobin SS and SC

In a comparative study of physiological changes in pregnant Nigerians, plasma volume measurements were performed in 75 healthy Nigerian women. They comprised 40 women with hemoglobin genotype AA (20 pregnant and 20 nonpregnant) and 35 women with hemoglobin genotype SS or SC (15 pregnant and 20 nonpregnant). Plasma volume was determined in the left lateral position using the Evans blue dye dilution technique (described by Dacie and Lewis) in the nonpregnant, at 16 and 36 weeks of gestation, and at 8 weeks postpartum.The mean plasma volume of 2044 ± 77.4 mL (SEM) in normal nonpregnant women with Hb AA was not significantly different from the mean plasma volume of 1931 ± 115 mL (SEM) found in nonpregnant sicklers. At 16 weeks' gestation there was no significant difference in the mean plasma volume of 2712 ± 209.8 mL (SEM) in pregnant women with HB AA and 2948 ± 165.8 mL (SEM) in pregnant sicklers. However, at 36 weeks the mean plasma volume of 3440 ± 223.7 mL (SEM) (68 percent increase compared with nonpregnant) in pregnant women with Hb AA was significantly higher (P < .02) than the mean plasma volume of 2312 ± 214.8 mL (SEM) (17 percent increase compared with nonpregnant) in sicklers.The mean birthweight of 3.17 ± 0.08 kg (SEM) in women with Hb AA was higher (P < .01) than that of 2.58 ± 0.15 kg (SEM) in sicklers. The perinatal mortality in sicklers was 133/thousand total births, while there was no fetal loss in the control. These data suggest a decrease or lack of intravascular volume expansion and evidence of uteroplacental insufficiency in sicklers.

The xerocytosis of Hb SC disease

Patients with Hb SC disease were found to have microcytic and hyperchromic red cell indices despite mild reticulocytosis. Iron deficiency anemia was ruled out by the finding of normal serum ferritin levels. In order to determine whether the microcytosis was due to coexistent alpha-thalassemia, restriction endonuclease mapping was performed on genomic DNA extracted from peripheral blood leukocytes. Patients with Hb SC disease had microcytic indices despite the presence of a full complement of four alpha-genes (alpha alpha/alpha alpha), suggesting that the microcytosis may be due to cellular dehydration (or xerocytosis), since the mean corpuscular hemoglobin concentration in Hb SC disease patients was significantly higher than in controls. This possibility was investigated further by the determination of RBC cation content. RBC Na levels were similar in SC and normal red cells. Hb SC RBCs, however, had significantly reduced K levels. These findings show that RBC cation content, and thus cell water, is decreased in Hb SC disease. The decreased RBC K level in the presence of normal cellular Na concentration suggests selective K loss that is not due to inhibition of the Na K pump. Ouabain-insensitive K+ efflux was increased to four times normal in SC cells. Cell dehydration was confirmed by the demonstration of increased high-density RBCs on discontinuous Stractan density gradients and by osmotic gradient ektacytometry. Cellular dehydration and its sequelae were worse in CC erythrocytes and milder in AC cells than in Hb SC red cells. Taken together, these data indicate that in Hb SC disease the RBCs are severely dehydrated and typically microcytic and hyperchromic. Hb SC RBCs seem to be dehydrated due to selective K loss. These findings suggest a functional interrelationship between Hb SC, the red cell membrane, and cation regulation.

Prepubertal growth and skeletal maturation in children with sickle cell disease

In a longitudinal study of 298 children with homozygous sickle cell (SS) disease and 157 children with hemoglobin SC disease, between birth and 9 years of age, observations of weight and height were made. These were compared with similar data derived from an age- and sex-matched group of 231 children with a normal hemoglobin (AA) genotype. Growth in children with SC disease was not significantly different from that in normal children, but children with SS disease had statistically significant, and progressive, deficits in both weight and height before 2 years of age. The average deficit approached 1 SD below the normal mean for age by 9 years. Observations of skeletal maturity, based on radiologic assessment of bone age at the wrist, were made on a proportion of these children at 5 and 8 years of age. Children with SS disease were significantly retarded at 8 years but not 5 years, which is consistent with increasing deficit in height. These observations confirm the early impact of SS disease on physical development and provide standards from which clinical expectations of growth may be derived. The relevance of these findings and their relationship to the characteristic delay in pubertal development is discussed together with a review of possible etiologic factors. The benign nature of SC disease is endorsed by the absence of an effect on growth in the prepubertal child.