Hyposplenism: A comprehensive review. Part I: Basic concepts and causes

Abstract

Hyposplenism is not a rare condition and can complicate a remarkable number of illnesses. The two most time-honored diseases associated with the development of hyposplenism are sickle cell anemia and celiac disease. Hyposplenism is relatively easy to recognize by typical changes observed on the peripheral blood smear; including Howell-Jolly bodies, monocytosis, lymphocytosis, and increased platelet counts. Diagnosis can be confirmed by pitted RBC counts or 99Tc-labelled radiocolloid scan of the spleen; wherever available. Diagnosis needs to be made promptly to institute pneumococcal vaccination in a timely fashion and to recognize and treat bacterial infections promptly and aggressively because of the tendency of hyposplenic subject to develop fatal invasive disease. Overwhelming pneumococcal sepsis accounts for the major mortality cases in hyposplenic subjects; however severe infections with other encapsulated bacteria and protozoa have been reported. Hyposplenic individuals may also be at a higher risk for vascular, autoimmune and thrombotic diseases and they may have a higher risk of developing solid tumors. The commonly used pneumococcal polysaccharide vaccine is ineffective in asplenic subjects, because it requires the presence of IgM memory B cells, and should be given before splenectomy. In splenectomized, and functionally hyposplenic subjects, the pneumococcal conjugate vaccine is more effective, because it utilizes a T cell dependent mechanism, and should be the preferred vaccine in these circumstances.

Hyposplenism: Comparison of different methods for determining splenic function

“…Although splenectomized individuals are evidently at risk for infection, there is a much larger, heterogeneous group of patients that has diminished splenic function or functional asplenia, associated with systemic disorders such as sickle cell disease (SCD), inflammatory bowel disease (IBD), and celiac disease [12,13]. In patients with homozygous sickle cell disease (HbSS), the function of the spleen is clearly diminished and a spectacular improvement in life expectancy has been observed following the introduction of a vaccination program and the administration of prophylactic antibiotics in children with HbSS [14].…”

Prevalence of Howell-Jolly Bodies Caused by Partial Splenic Embolization for Portal Hypertension

“…However, PSE can induce an asplenic state, irrespective of the infarction rate. The presence of HJBs on peripheral blood smears is reported to be useful for assessing the splenic function (8,23,24). When HLBs are present, the pneumococcal vaccine should be administered immediately in order to prevent OPSI and PSS.…”

Low immunoglobulin M memory B-cell percentage in patients with heterotaxy syndrome correlates with the risk of severe bacterial infection

“…In our previous study, the annual infection rate was 7.1% in the first 2 y of life, 3.3% between the ages of 2 and 5 y, and 1.5% after the age of 5 y (6). Other lymphoid organs, such as the lymph nodes and enteric lymphoid tissue, may substitute for splenic function with age and reduce the risk of SBI in some patients (11). Because of individual variations and changes of immune function over time, measuring splenic function is essential in identifying patients at high-risk of SBI.…”

“…The risk of SBI in heterotaxy patients is highest before 2 y of age, and decreases gradually with age (6,11), possibly because lymphoid organs, such as the lymph nodes and enteric lymphoid tissue, may substitute for the splenic immune function in some patients as age increases (12). Although the spleen is a vital immunologic organ, there is still no simple and effective method for evaluating its function (13).…”