Fatal pneumococcal septicemia in hemoglobin SC disease

Acute Splenic Sequestration Crisis in a 70-Year-Old Patient With Hemoglobin SC Disease

A 70-year-old African American female with a past medical history significant for chronic bilateral shoulder pain and reported sickle cell trait presented with acute-onset bilateral thoracolumbar pain radiating to her left arm. Two days after admission, Hematology was consulted for severely worsening microcytic anemia and thrombocytopenia. Examination of the patient's peripheral blood smear from admission revealed no cell sickling, spherocytes, or schistocytes. Some targeting was noted. A Coombs test was negative. The patient was eventually transferred to the medical intensive care unit in respiratory distress. Hemoglobin electrophoresis confirmed a diagnosis of hemoglobin SC disease. A diagnosis of acute splenic sequestration crisis complicated by acute chest syndrome was crystallized, and red blood cell exchange transfusion was performed. Further research is necessary to fully elucidate the pathophysiology behind acute splenic sequestration crisis, and the role of splenectomy to treat hemoglobin SC disease patients should be better defined.

How we prevent and manage infection in sickle cell disease

Sickle cell disease (SCD) affects approximately 100,000 people in the US, 12,500 in the UK, and millions worldwide. SCD is typified by painful vaso-occlusive episodes, haemolytic anaemia and organ damage. A secondary complication is infection, which can be bacterial, fungal or viral. Universal newborn screening, routine use of penicillin prophylaxis, availability of conjugated vaccines against S. pneumoniae and comprehensive care programmes instituted during the past few decades in industrialized countries have dramatically reduced childhood mortality and improved life expectancy. Yet patients with SCD remain at increased risk of infection. Unfortunately, the treatment of most bacterial infections that are common in SCD is not based on the results of randomized controlled clinical trials. In their absence, treatment decisions are based on consensus guidelines, clinical experience or adapting treatment applied in other diseases. This leads to wide variation in treatment among institutions and even between treating physicians in a single institution. Prevention of infection, when possible, is most important and we focus on prevention through targeted prophylaxis and vaccination. We will share our management strategies for managing the more common infections in SCD and provide the rationale for our recommendations.

Prophylactic penicillin after 5 years of age in patients with sickle cell disease: a survey of sickle cell disease experts

BACKGROUND

Since the publication of the Prophlyactic Penicillin Study II in 1995, the management of penicillin prophylaxis for children with sickle cell disease (SCD) after 5 years of age has been controversial. In this study, we sought to describe current practice patterns of pediatric hematologists related to cessation of penicillin prophylaxis for children with SCD after 5 years of age.

PROCEDURE

We performed a cross-sectional, electronic survey of pediatric hematologists with expertise in SCD to examine practices regarding penicillin prophylaxis in children with SCD after 5 years of age. We also investigated factors potentially associated with continuation of penicillin prophylaxis using the Jonckheere-Terpstra test and Fisher's exact test.

RESULTS

Of the 106 physicians surveyed from 76 centers, 84% completed the survey. Among respondents, 76% routinely recommended cessation of penicillin prophylaxis after 5 years of age. The practice of routinely continuing penicillin after 5 years of age was associated with decreased concern about antibiotic resistance in Streptococcus pneumoniae (P = 0.01), with the usage of prophylactic penicillin in mild SCD genotypes (sickle hemoglobin-C disease and sickle β(+) thalassemia, P = <0.001), and with increasing use of other preventive evaluations (e.g., MRI for silent stroke) in childhood (P = 0.05).

CONCLUSION

Most pediatric hematologists with an SCD expertise recommend cessation of prophylactic penicillin after 5 years of age.

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.

Streptococcus pneumoniae sepsis and meningitis during the penicillin prophylaxis era in children with sickle cell disease

The purpose of this study was to determine the age-related risks, disease-specific risks, and characteristics of serious pneumococcal infections in children with sickle cell disease (SCD) while penicillin prophylaxis was standard. The clinical experiences of three pediatric sickle cell programs spanning January 1, 1992, to May 31, 1998, were combined. Data were collected regarding the patients followed up and the characteristics of bacteremia and meningitis cases. Forty-seven pneumococcal infections (44 bacteremia, 3 meningitis) among 40 patients with SCD were observed. Forty infections occurred in children with homozygous hemoglobin S (SS) during 4108 patient-years at a median age of 22 months; 7 occurred in double heterozygous hemoglobin SC (SC) children during 1777 patient-years at a median age of 23 months. Ten infections occurred among 9 SS children 5 years or older. Most children in whom infections developed were reportedly taking prophylactic penicillin and when older than 24 months old had received Pneumovax (Merck & Co., Inc., West Point, PA, U.S.A. The following pneumococcal serotypes were identified in 15 cases studied: 6A, 6B, 9V, 14, 15B, 18B, 18F, 19F, and 23F. Infections resulted in five deaths and two strokes. The observed severe pneumococcal infection rate in SS children younger than 5 years was less than that reported before penicillin prophylaxis, supporting routine penicillin prophylaxis in this specific population. The optimal duration of penicillin prophylaxis in older children with SCD remains unknown. The administration of 7-valent Prevnar (Wyeth Lederle Vaccines, Philadelphia, PA, U.S.A.) to children younger than 24 months old with SCD should be beneficial, based on the serotype data.

Pneumococcal vaccination of children

Streptococcus pneumoniae is the most frequent cause of invasive bacterial infection in children younger than 2 years of age, reaching a peak incidence at 6 to 12 months of age. Pneumococci also cause many cases of pneumonia, sinusitis, and otitis media. Incidence rates of invasive infection in children with sickle cell disease, acquired or congenital splenectomy, or human immunodeficiency virus infection are 20- to 100-fold higher than are those of healthy children during the first 5 years of life. Other healthy children, such as those of American Indian, Native Alaskan, or African American descent, also have high rates of invasive infection, and those children enrolled in out-of-home care may have modestly increased risks. Pneumococcal polysaccharide polyvalent vaccines have been available for more than 2 decades but are limited in their usefulness for children because of their inability to induce protective antibody responses in children younger than 2 years of age and lack of immunologic memory. In contrast, pneumococcal protein conjugate vaccines induce presumptive protective responses in infants younger than 6 months, and immunologic memory further enhances responses after booster doses are given. Currently, a single heptavalent pneumococcal protein conjugate vaccine is licensed for use in the United States and is recommended for routine administration to all children, beginning at 2 months of age. It also is recommended for children between 24 and 59 months of age who are at high risk of acquiring invasive 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.

American Academy of Pediatrics. Committee on Infectious Diseases. Technical report: prevention of pneumococcal infections, including the use of pneumococcal conjugate and polysaccharide vaccines and antibiotic prophylaxis

Pneumococcal infections are the most common invasive bacterial infections in children in the United States. The incidence of invasive pneumococcal infections peaks in children younger than 2 years, reaching rates of 228/100,000 in children 6 to 12 months old. Children with functional or anatomic asplenia (including sickle cell disease [SCD]) and children with human immunodeficiency virus infection have pneumococcal infection rates 20- to 100-fold higher than those of healthy children during the first 5 years of life. Others at high risk of pneumococcal infections include children with congenital immunodeficiency; chronic cardiopulmonary disease; children receiving immunosuppressive chemotherapy; children with immunosuppressive neoplastic diseases; children with chronic renal insufficiency, including nephrotic syndrome; children with diabetes; and children with cerebrospinal fluid leaks. Children of Native American (American Indian and Alaska Native) or African American descent also have higher rates of invasive pneumococcal disease. Outbreaks of pneumococcal infection have occurred with increased frequency in children attending out-of-home care. Among these children, nasopharyngeal colonization rates of 60% have been observed, along with pneumococci resistant to multiple antibiotics. The administration of antibiotics to children involved in outbreaks of pneumococcal disease has had an inconsistent effect on nasopharyngeal carriage. In contrast, continuous penicillin prophylaxis in children younger than 5 years with SCD has been successful in reducing rates of pneumococcal disease by 84%. Pneumococcal polysaccharide vaccines have been recommended since 1985 for children older than 2 years who are at high risk of invasive disease, but these vaccines were not recommended for younger children and infants because of poor antibody response before 2 years of age. In contrast, pneumococcal conjugate vaccines (Prevnar) induce proposed protective antibody responses (>.15 microg/mL) in >90% of infants after 3 doses given at 2, 4, and 6 months of age. After priming doses, significant booster responses (ie, immunologic memory) are apparent when additional doses are given at 12 to 15 months of age. In efficacy trials, infant immunization with Prevnar decreased invasive infections by >93% and consolidative pneumonia by 73%, and it was associated with a 7% decrease in otitis media and a 20% decrease in tympanostomy tube placement. Adverse events after the administration of Prevnar have been limited to areas of local swelling or erythema of 1 to 2 cm and some increase in the incidence of postimmunization fever when it is given with other childhood vaccines. Based on data in phase 3 efficacy and safety trials, the US Food and Drug Administration has provided an indication for the use of Prevnar in children younger than 24 months.

Antibody responses to Haemophilus influenzae type b conjugate vaccine in sickle cell disease

OBJECTIVE

To investigate the immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccines in children with sickle cell disease.

DESIGN

Open study.

SETTING

Haemoglobinopathy clinic.

SUBJECTS

Children with homozygous haemoglobin SS disease (HbSS), sickle haemoglobin C disease (HbSC), and sickle-beta thalassaemia disease (HbS-beta Thal).

INTERVENTIONS

Children over the age of 2 years received a single dose of Hib-tetanus toxoid conjugate vaccine (PRP-T).

MAIN OUTCOME MEASURES

Antibody response to Hib polysaccharide (PRP) approximately one month after vaccination.

RESULTS

77 children over the age of 2 years were studied,, 55 with HbSS, 16 with HbSC, and six with HbS-beta Thal. Before vaccination, 44% had anti-PRP IgG titres less than the level associated with long term protection (1.0 microgram/ml). After a single dose of PRP-T all children mounted an antibody titre > 1 microgram/ml. Geometric mean anti-PRP IgG titre achieved postvaccination (45.2 micrograms/ml 95% confidence interval (CI) 31.6 to 64.8) was comparable to that of a healthy population. Children with HbSC, however, had a significantly higher antibody titre postvaccination (91.1 micrograms/ml; 95% CI 32.7 to 254.4) than the children with HbSS (36.7 micrograms/ml; 95% CI 25.1 to 52.9).

CONCLUSIONS

Children with a diagnosis of sickle cell disease who are over the age of 2 years make a vigorous antibody response to a single dose of PRP-T vaccine and hence we suggest unimmunised individuals in this group should receive a single dose of a Hib conjugate vaccine.

Hematologic profile and lymphocyte subpopulations in hemoglobin SC disease: comparison with hemoglobin SS and black controls. The Transfusion Safety Study Group

Compared with subjects with homozygous SS disease (Hb SS), persons with hemoglobin SC (Hb SC) are known to have a more gradual loss of splenic function, a lower incidence of bacterial infections, and fewer end-organ failures. We studied hematological indices and lymphocyte subpopulations of 27 Hb SC subjects and compared them with 173 Hb SS patients and 131 black controls. Hb SC patients had higher hemoglobin levels than Hb SS subjects, lower total leukocyte, granulocyte, monocyte, and lymphocyte counts. Platelets decreased with age but not significantly, instead of increasing as among Hb SS patients. Mononuclear cells were generally similar to controls with the exception of CD8+HLA-DR+ counts resembling Hb SS. Hematologic changes in Hb SC are limited to moderate granulocytosis in children and adults, mild monocytosis in adults, and increased activation of just one lymphocyte subset among those measured.

Sickle cell disease

The identification of genetic mutation that causes sickle cell disease 35 years ago has not yet led to a widely applicable, specific therapy that corrects the underlying abnormality of hemoglobin. Nevertheless, recent progress in understanding the pathophysiology and natural history of sickling disorders has led directly to important prophylactic and supportive therapies that have markedly reduced morbidity and prolonged life expectancy. This is particularly true for manifestations of sickle cell disease that result from damage to the spleen, lungs, and brain. New strategies for specific therapy, including expanded use of chronic transfusions, bone marrow transplantation, and hydroxyurea, now offer hope for prevention of many or all of the hemolytic and vaso-occlusive manifestations of sickle cell disease.

Bacteremia in children with sickle hemoglobin C disease and sickle beta(+)-thalassemia: is prophylactic penicillin necessary?

OBJECTIVE

To characterize the incidence of bacteremia and its potential for progression to septicemia in children with sickle hemoglobin C disease and sickle beta(+)-thalassemia to assess the need for penicillin prophylaxis.

STUDY DESIGN

Retrospective chart review of the frequency and natural history of bloodstream infection in such patients not receiving prophylactic penicillin therapy and followed up in a single institution.

RESULTS

During more than 842 patient-years of observation in 242 patients with sickle hemoglobin C disease, 15 episodes of bacteremia occurred in nine patients. Septicemia was fatal in one patient. The overall incidence of bacteremia, 1.8 events per 100 patient-years (95% confidence limits: 0.8, 2.8) in patients with sickle hemoglobin C disease, was similar to that in hematologically normal children. One episode of bacteremia occurred in a patient with sickle beta(+)-thalassemia.

CONCLUSIONS

The incidence of bacteremia is not increased in young patients with sickle hemoglobin C disease and sickle beta(+)-thalassemia. Further, unlike its course in children with sickle cell anemia, it rarely evolves into life-threatening septicemia. This probably results from the maintenance of relatively intact splenic function during infancy and early childhood in patients with sickle hemoglobin C disease and sickle beta(+)-thalassemia. Prophylactic penicillin therapy may not be required in these patients.

Life-threatening infection in two children with hemoglobin S-beta-thalassemia

Life-threatening infections with Streptococcus pneumoniae and parvovirus occurred in two patients with hemoglobin S-beta-thalassemia. We recommend that acute febrile illnesses in the presence of any hemoglobinopathy be considered potentially life threatening, and managed accordingly.