Acute splenic complications in children with sickle cell-hemoglobin C disease

The clinical spectrum of HbSC sickle cell disease-not a benign condition

Sickle cell disease (SCD) includes a group of heterogenous disorders that result in significant morbidities. HbSS is the most common type of SCD and HbSC is the second most common type of SCD. The prevalence of HbSC disease in the United States and United Kingdom is ~1 in 7174 births and 1 in 6174 births respectively. Despite its frequency, however, HbSC disease has been insufficiently studied and was historically categorized as a more 'mild' form of SCD. We conducted this study of HbSC disease as part of the NHLBI funded Sickle Cell Disease Implementation Consortium (SCDIC). The SCDIC registry included 2282 individuals with SCD, ages 15-45 years of whom 502 (22%) had HbSC disease. Compared with people with sickle cell anaemia (SCA), the study found that people with HbSC disease had a higher frequency of splenomegaly (n (%) = 169 (33.7) vs. 392 (22.1)) and retinopathy (n (%) = 116 (23.1) vs. 189 (10.6)). A Many people with HbSC also had avascular necrosis (n (%) = 112 (22.3)), pulmonary embolism (n (%) = 43 (8.6)) and acute chest syndrome (n (%) = 228 (45.4)) demonstrating significant disease severity. HbSC disease is more clinically severe than was previously recognized and deserves additional evaluation and targeted treatments.

The German sickle cell disease registry reveals a surprising risk of acute splenic sequestration and an increased transfusion requirement in patients with compound heterozygous sickle cell disease HbS/β-thalassaemia and no or low HbA expression

Patients with sickle cell disease (SCD) in Germany exhibit a substantial genetic diversity in the β-globin genotype. Data collected by the national German SCD registry reflect this diversity and allowed us to analyze the phenotypes associated with different SCD genotypes. Our study focused on 90 patients with HbS/β-thalassaemia (HbS/β-thal) and compared these to patients with HbSS and HbSC. Patients with HbS/β-thal were classified into three groups: HbS/β0-thal (no HbA), HbS/β+-thal (HbA < 14%), and HbS/β++-thal (HbA≥14%). In comparison to HbSS, patients with HbS/β++-thal had higher Hb-levels, lower hemolytic activity and rarely required red blood cell transfusions. HbS/β0-thal and HbS/β+-thal closely resembled each other and are jointly referred to as HbS/β0/+-thal. Compared to HbSS, patients with HbS/β0/+-thal experienced a similar frequency of vasoocclusive crises and degree of hemolysis. However, the frequency of red blood cell transfusions (0.6 vs. 0.39/year, p = .0049) and splenic sequestration crises (42.4 vs. 15.5% of patients, p = 3.799e-05) was higher in HbS/β0/+-thal than in HbSS, but close to zero in HbS/β++-thal. In conclusion, the level of HbA expression determines the phenotype of HbS/β+-thal. HbS/β-thal expressing no or little HbA is hematologically similar to HbSS, but causes a previously unknown high risk of splenic sequestration.

Pediatric splenic infarction: Assessment of associated clinical conditions and outcome

Pediatric splenic infarction (SI) is rare yet clinically significant. Publications regarding this complication are mostly limited to case reports. This is a retrospective study examining SI etiology, clinical presentation, management, and outcomes among children. Twenty-two patients (median age: 7.9 years) were included, mostly with pre-existing hematological diseases. Splenomegaly (72%), thrombocytopenia, and anemia were common. Most of the patients did not receive antithrombotic therapy yet only two patients experienced recurrences. During follow up 36% of patients died, however no fatalities were attributed to thrombotic or bleeding complications.

Massive Splenic Infarction in a Child With Sickle Cell Disease on Chronic Transfusion Therapy

Massive splenic infarction (MSI) is a rare complication of sickle cell disease, as the spleen generally atrophies within the first few years of life. We report a case of MSI in a 12-year-old boy with homozygous sickle cell anemia (Hb SS) whose chronic transfusion therapy resulted in hypersplenism. The occurrence of a complicated MSI in our patient should perhaps further encourage elective splenectomy in such patients, despite known potential perioperative complications and postsplenectomy risks of infection and thrombosis.

Clinical and hematological profile in a newborn cohort with hemoglobin SC

OBJECTIVES

Hemoglobin SC is the second most common variant of sickle-cell disease worldwide, after hemoglobin SS. The objectives of the study were to describe the clinical and laboratory characteristics of hemoglobin SC disease in children from a newborn screening program and treated at a blood center.

METHODOLOGY

This study assessed a cohort of 461 infants born between 01/01/1999 and 12/31/2012 and followed-up until 12/31/2014. Clinical events were expressed as rates for 100 patient-years, with 95% confidence intervals. Kaplan-Meier survival curves were created.

RESULTS

The median age of patients was 9.2 years; 47.5% were female. Mean values of blood tests were: hemoglobin, 10.5g/dL; reticulocytes, 3.4%; white blood cells, 11.24×10⁹/L; platelets, 337.1×10⁹/L; and fetal hemoglobin, 6.3%. Clinical events: acute splenic sequestration in 14.8%, blood transfusion 23.4%, overt stroke in 0.2%. The incidence of painful vaso-occlusive episodes was 51 (48.9-53.4) per 100 patient-years and that of infections, 62.2 episodes (59.8-64.8) per 100 patient-years. Transcranial Doppler ultrasonography (n=71) was normal given the current reference values for SS patients. Hydroxyurea was given to ten children, all of whom improvement of painful crises. Retinopathy was observed in 20.3% of 59 children who underwent ophthalmoscopy. Avascular necrosis was detected in seven of 12 patients evaluated, predominantly in the left femur. Echocardiogram compatible with pulmonary hypertension was recorded in 4.6% of 130 children, with an estimated average systolic pulmonary artery pressure of 33.5mmHg. The mortality rate from all causes was 4.3%.

CONCLUSIONS

Clinical severity is variable in SC hemoglobinopathy. Several children have severe manifestations similar to those with SS disease.

Knowledge insufficient: the management of haemoglobin SC disease

Although haemoglobin SC (HbSC) accounts for 30% of sickle cell disease (SCD) in the United States and United Kingdom, evidence-based guidelines for genotype specific management are lacking. The unique pathology of HbSC disease is complex, characterized by erythrocyte dehydration, intracellular sickling and increased blood viscosity. The evaluation and treatment of patients with HbSC is largely inferred from studies of SCD consisting mostly of haemoglobin SS (HbSS) patients. These studies are underpowered to allow definitive conclusions about HbSC. We review the pathophysiology of HbSC disease, including known and potential differences between HbSS and HbSC, and highlight knowledge gaps in HbSC disease management. Clinical and translational research is needed to develop targeted treatments and to validate management recommendations for efficacy, safety and impact on quality of life for people with HbSC.

Hydroxyurea decreases hospitalizations in pediatric patients with Hb SC and Hb SB+ thalassemia

PURPOSE

Patients with hemoglobin SC (Hb SC) and hemoglobin SB+ (Hb SB+) thalassemia suffer from frequent hospitalizations yet strong evidence of a clinical benefit of hydroxyurea (HU) in this population is lacking. Patients with recurrent hospitalizations for pain crisis are offered HU at our institution based on small cohort data and anecdotal benefit. This study identifies outcomes from a large cohort of patients with Hb SC and SB+ thalassemia who were treated with HU for 2 years.

MATERIALS AND METHODS

A retrospective review was conducted of 32 patients with Hb SC and SB+ thalassemia who were treated with HU. We reviewed the number, and reasons for hospitalization in the 2 years prior to, and 2 years post-HU treatment as well as laboratory changes from baseline, over 1 year.

RESULTS

Patients with Hb SC and SB+ thalassemia started on HU for frequent pain, had a significant reduction in hospitalizations over 2 years as compared to the 2 years prior to HU initiation (mean total hospitalizations/year: pre-HU: 1.6 vs post-HU 0.4 hospitalizations, P<0.001; mean pain hospitalizations/year: pre-HU 1.5 vs post-HU 0.3 hospitalizations, P<0.001). Patients demonstrated hematologic changes including an increase in percent fetal hemoglobin (%HbF) pre-post HU (4.5% to 7.7%, P=0.002), mean corpuscular volume (74 to 86 fL, P<0,0001), and decrease in absolute neutrophil count (5.0 to 3.2×10(9)/L, P=0.007). Patients with higher doses of HU demonstrated the greatest reduction in hospitalizations but this was unrelated to absolute neutrophil count.

CONCLUSION

This cohort of patients with Hb SC and SB+ thalassemia provides additional support for using HU in patients with recurrent hospitalizations for pain. A large randomized multicenter trial of HU to reduce pain admissions should be conducted to confirm these data and provide much needed evidence based recommendations for this population.

Outcome of splenectomy in children younger than 4 years with sickle cell disease

PURPOSE

Removal of the spleen in patients younger than 4 years has been reported to carry an increased risk of postsplenectomy sepsis and has not been universally accepted. We reviewed our experience with splenectomy in children with acute splenic sequestration crisis (ASSC) younger than 4 years.

METHODS

The study involved retrospective review of demographic and operative data, number of ASSC, operative complications, infections, and death.

RESULTS

From 1993 to 2008, 53 patients (28 males, 25 females) younger than 4 years had open (43.8%) or laparoscopic (56.6%) splenectomy after one or more events of ASSC. Six (11.3%) were younger than 18 months, 28 (52.8%) were 18 to 24 months old, and 21 (39.6%) were 24 to 48 months old. Operative complications were diaphragm laceration (laparoscopy, n = 3; 5.7%) and reoperation for bleeding (open, n = 1; 1.8%). Length of stay was similar for laparoscopic (3.6 days) vs open (3.8 days) splenectomy. Mean postoperative follow-up was 5.6 years. In 353 postsplenectomy admissions, 3 (5.7%) patients had positive blood cultures requiring treatment. Three (5.7%) patients died within the 15-year study period; one (1.8%) had documented pneumococcal sepsis.

DISCUSSION

The advantage of early splenectomy may outweigh the risks of long-term transfusion. Splenectomy in young children with sickle cell disease carries a low risk of postsplenectomy sepsis with appropriate vaccination and prophylactic antibiotics. We conclude that splenectomy in young children with ASSC is safe and effective, especially with penicillin prophylaxis and improved vaccination strategies.

Acute splenic complications and implications of splenectomy in hemoglobin SC disease

Splenectomy indications and outcome were evaluated in 124 adults with hemoglobin SC disease (Hb SC). Twelve patients (9.6%) required splenectomy. There was a significant difference between the splenectomy group and the non-splenectomy group, respectively, regarding Hb levels (median 7.2 g/dL vs. 12.5 g/dL, P < 0.0001), platelet counts (median 146 x 10(6)/L vs. 275 x 10(6)/L, P = 0.031), palpable spleen rate (66% vs. 16%, P = 0.0003%), acute chest syndrome frequency (75% vs. 12%P = 0.0004) and cholecystectomy rate (66% vs. 13%, P = 0.0004). No significant morbidity or mortality occurred postsplenectomy. There is a subgroup of Hb SC patients requiring splenectomy, in which splenectomy is effective. Although it appears to be safe regarding short-term complications of surgery, long-term adverse effects such as infections have to be evaluated cautiously.

Acute Splenic Sequestration Crisis Resembling Sepsis in an Adult with Hemoglobin SC Disease

Acute splenic sequestration crisis (ASSC) is a common complication of sickle cell anemia in children. ASSC is generally not seen in adults with the SS genotype but occasionally can be seen in adults with the SC genotype. We present a case of fulminant ASSC in an adult with hemoglobin SC who developed high fever, intense abdominal pain, leukocytosis, and jaundice.

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.

Outcome in hemoglobin SC disease: a four-decade observational study of clinical, hematologic, and genetic factors

Over the past 40 years, we observed 284 subjects with hemoglobin SC disease (Hb SC) for 2,837 person-years. We examined the association of the course of clinical events with hematologic and genetic factors. The mean entry age was 21 years, although 15% entered before one year of age. The mean Hb concentration was 11.3 g/dL, the mean fetal hemoglobin was 2.5%, and the mean MCV was 84.4 fL. Twenty-five subjects died at a median age of 37 years. Chronic organ-specific complications occurred in 112 subjects (39.4%), with advanced retinopathy in 65 subjects (22.9%) and osteonecrosis (avascular necrosis) in 42 subjects (14.8%). We identified the beta-globin haplotypes in 82 subjects and the alpha-gene status in 79. Twenty-nine percent had alpha-thalassemia-2. The beta(CI) haplotype was present in 85.4%. We found a decreased incidence of retinopathy in the beta(CI) subjects compared to the non-beta(CI) subjects (33% vs. 67%; P = 0.049) with a later mean onset age (29 years vs. 21 years; log-rank test, P= 0.026). We also found a consistent pattern of decreased morbidity in subjects who had alpha-thalassemia-2 in comparison to those who did not. We found a reduced risk of chronic organ-specific complications (log-rank test, P= 0.003), lower incidence of sickle crisis (48% vs. 80%, P= 0.001), later onset of gallbladder disease (age of onset: 55 years vs. 34 years; P= 0.055), and lower risk of osteonecrosis (log-rank test, P= 0.024). Our findings suggest that Hb SC subjects who have not inherited alpha-thalassemia-2 might benefit from erythrocyte rehydration therapy.

Palpable splenomegaly in children with haemoglobin SC disease: haematological and clinical manifestations

This study aimed to investigate the prevalence of palpable splenomegaly in children with haemoglobin SC (Hb SC) disease, and to determine the haematological and clinical manifestations of splenomegaly in this patient population. We performed a retrospective chart review of 100 patients with Hb SC over 2 years of age followed by the Duke University Paediatric Sickle Cell Program with serial physical examinations and laboratory measurements. Palpable splenomegaly was present in 34% of patients and was more common in males (P = 0.029). Children with splenomegaly had a significantly lower average haemoglobin concentration (10.3 vs. 10.8 g/dl, P = 0.011) and lower platelet count (237 vs. 314 x 109/l, P < 0.001) than those without splenomegaly. Children with measurements both before and after the onset of splenomegaly had a significant decrease in the platelet count (279 vs. 216 x 109/l, P < 0.001) and white blood cell count (9.1 vs. 7.9 x 109/l, P = 0.04) after splenomegaly was identified. Clinical complications included acute splenic sequestration in 12% of children (median age 5.4 years), and hypersplenism with chronic thrombocytopenia in another 10% of patients (median age 10.6 years). Splenomegaly is a common physical finding in children with Hb SC disease and is often associated with mild cytopenias. Clinical complications of splenomegaly include acute splenic sequestration in younger patients and hypersplenism with chronic thrombocytopenia in older children.