Letter: Thyrotoxicosis associated with splenic atrophy

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

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 in alcoholic cirrhosis, facts or artifacts? A comparative analysis with non-alcoholic cirrhosis and extrahepatic portal venous obstruction

BACKGROUND AND AIMS

Hyposplenism has been described in patients with alcoholic cirrhosis (AC). However, no data are available regarding hyposplenism in patients with non-alcoholic cirrhosis (NAC) and other forms of portal hypertension such as extrahepatic portal venous obstruction (EHPVO). The aim is to study the splenic functions in patients with AC, NAC, and EHPVO.

METHODS

Splenic functions were assessed consecutively in 22 patients with AC, 21 with NAC, and 23 with EHPVO. The tests included pitted red blood cells (RBC; %) and Howell-Jolly bodies in the peripheral smear. Pitted RBCs > 2% with or without the presence of Howell-Jolly bodies were taken as indicators of hyposplenism. The splenic function in each group was compared with age-matched controls.

RESULTS

Hyposplenism was found in 10 (45.45%) patients with AC, six (28.57%) with NAC and one (4.34%) with EHPVO. The mean pitted RBCs were significantly increased in patients with AC (mean 4.93 +/- 1.36% vs control 1.22 +/- 0.17%, P < 0.05), but not so with NAC (2.01 +/- 0.69%) and EHPVO (mean 0.99 +/- 0.1% vs control 0.66 +/- 0.1%, P > 0.05). Howell-Jolly bodies were seen in only four patients. The mean pitted RBCs were significantly higher among patients who were actively consuming alcohol (9.14 +/- 3.35%) compared to those who abstained at least for more than 24 weeks (2.0 +/- 1.3%, P < 0.05).

CONCLUSION

Hyposplenism is more common in AC patients, particularly those who are actively consuming alcohol compared with those who abstain. Patients with NAC have a lower incidence of hyposplenism, while in EHPVO patients, it is uncommon.

Asplenism and systemic lupus erythematosus

Although functional hyposplenism, secondary to Fc-receptor blockage by circulating immune complexes saturation, has been described in systemic lupus erythematosus (SLE), only few cases of complete asplenism have been reported. We observed a 60-year-old woman with congenital asplenism who presented with active SLE. The course and the clinical characteristics of such patients are reviewed and the relationship between the asplenic state and initiation and severity of SLE are discussed. These patients are at high risk for fatal pneumococcemia and pneumococcal vaccine is recommended even if long term results are still conflicting.

Splenic function: physiology and splenic hypofunction

A wide variety of disorders can result in diminished splenic function. The pathophysiology appears to be clearly defined in some instances, such as congenital asplenia and disorders of splenic vascular obstruction or congestion. In others, such as the autoimmune and GI disorders, the mechanism remains poorly defined. Further research is needed. The hyposplenia which occurs in many of these disorders has been associated with an increased risk of life-threatening, overwhelming bacterial sepsis. In other instances, this complication has not been reported. This certainly should not be interpreted to mean that it cannot occur. The risk of septicemia in hyposplenic disorders is rarely above 10 to 15%. In disorders with minimal inhibition of splenic function, the incidence of sepsis would presumably be less than the 1.5% incidence following surgical splenectomy for trauma. Considering these data, a very large number of patients would have to become asplenic before it would be likely that one would develop sepsis. Furthermore, the lack of awareness of the possibility of hyposplenia-related sepsis in many of these disorders may cause such occurrences to go unrecognized. Finally, since the risk of sepsis is probably less in hyposplenic adults as compared to children, studies on adults may underestimate the incidence of this complication in children. Many of the disorders reported to cause hyposplenia in adults have not been noted to do so in children. In instances such as celiac disease, it may take many years for the complication to manifest so that it would be unlikely for a child to manifest hyposplenia during childhood. However, in other instances, not enough children have been studied to be confident that the hyposplenia and its associated risk of sepsis are not complications that occur in children. Hyposplenia-related bacterial septicemia is a catastrophic complication. If a patient develops a disorder that is potentially associated with hyposplenia, the patient should be observed for signs of asplenia in the peripheral blood. If the technique is available, quantitation of red cell pits should be performed. If not, other studies of splenic function such as radionuclide scans should be considered, depending on the incidence of hyposplenia in that particular disorder. If evidence of asplenia develops, pneumococcal vaccine should be administered, penicillin prophylaxis should be considered, significant febrile episodes should be managed aggressively, and probably most importantly, the patient and family should be carefully educated about this complication. Most deaths from hyposplenia-related septicemia are preventable.

Pitted erythrocytes in splenectomized subjects with congenital spherocytosis and in subjects splenectomized for other reasons

Pitted erythrocytes counts are used in the quantitative assessment of functional hyposplenism and in the prediction of recurrence of splenic function in splenectomized subjects. Pitted erythrocyte counts were investigated in 16 patients splenectomized for hereditary spherocytosis, in 21 patients splenectomized for other reasons and in 23 healthy controls. In both groups of splenectomized patients the pitted erythrocyte counts were equally increased compared with the healthy controls.

The spleen: development and functional evaluation

Despite the fact that the spleen has multiple functions, only one has been widely used for evaluation of the organ by imaging techniques (phagocytosis of 99mTc sulfur colloid). The usual splenic uptake of this radiocolloid can by used to determine the size, location, and integrity of the organ. A major use of splenic radiocolloid imaging has been in the study of congenital defects. Thus, eventration of the diaphragm, accessory spleens, splenogonadal fusion, the asplenia and polysplenia syndromes, and the wandering spleen are amenable to study by means of intravenously administered radiocolloid. Interference with the splenic uptake of radiocolloid can be either focal or generalized (as in functional asplenia). Imaging of the spleen has a major role in evaluating suspected trauma of the organ and in following its clinical course. The return of splenic function after splenectomy (splenosis or accessory spleens) can be documented by radionuclide imaging, and likely by hematologic techniques when the volume of tissue is sufficiently large. The detection of intrasplenic lesions is important in tumor staging and as an alerting sign to an ongoing process.

Splenic function: normal, too much and too little

This review is concerned with normal splenic function, mechanisms and consequences of splenomegaly, hypersplenism, the medical indications for splenectomy and the various aspects of hyposplenism. The potential probelm of lethal septicemia in hyposplenic or asplenic patients is also considered.