Antibody-mediated killing of suppressor T lymphocytes as a possible cause of macroglobulinemia in the tropical splenomegaly syndrome

Hyperreactive Malarial Splenomegaly Syndrome--Can the Diagnostic Criteria Be Improved?

Hyperreactive Malarial Splenomegaly Syndrome (HMSS) was described and defined before sensitive tests for malaria were available. We present a series of seven individuals who were referred to our clinics with possible HMSS. Chronic malaria was demonstrated in those successfully treated but not in those who failed to respond to therapy. This observation suggests that the newer molecular malaria assays have a role to play in the identification of individuals who are likely to respond to treatment for HMSS in non-endemic regions.

[Hyper-reactive malarial splenomegaly]

Hyper-reactive malarial splenomegaly is a rare and severe form of chronic malaria. This condition is a common cause of splenomegaly in endemic areas. The pathophysiology of hyper-reactive malarial splenomegaly involves an intense immune reaction (predominantly B cell-driven) to repeated/chronic infections with Plasmodium sp. The diagnosis may be difficult, due to a poorly specific clinical presentation (splenomegaly, fatigue, cytopenias), a long delay between residence in a malaria-endemic area and onset of symptoms, and a frequent absence of parasites on conventional thin and thick blood smears. A strongly contributive laboratory parameter is the presence of high levels of total immunoglobulin M. When the diagnostic of hyper-reactive malarial splenomegaly is considered, search for anti-Plasmodium antibodies and Plasmodium nucleic acids (genus and species) by PCR is useful. Diagnosis of hyper-reactive malarial splenomegaly relies on the simultaneous presence of epidemiological, clinical, biological and follow-up findings. Regression of both splenomegaly and hypersplenism following antimalarial therapy allows the differential diagnosis with splenic lymphoma, a common complication of hyper-reactive malarial splenomegaly. Although rare in Western countries, hyper-reactive malarial splenomegaly deserves increased medical awareness to reduce the incidence of incorrect diagnosis, to prevent progression to splenic lymphoma and to avoid splenectomy.

Hyper-reactive malarial splenomegaly and splenic infarct in a caucasian toddler

A 4-year-old boy from the United States had been staying in Indonesia for five months when he presented with fever, severe lethargy, progressive weight loss, and abdominal distension. He was first diagnosed with Plasmodium vivax infection in Indonesia and received treatment with chloroquine. However, his condition continued to deteriorate and he required erythrocyte transfusion for severe anemia. Three weeks into his illness, he was found to have low parasitemia with Plasmodium falciparum with massive hepatosplenomegaly in Singapore. A splenic infarct was also documented on computed tomography. Treatment with atovaquone-proguanil resulted in stabilization of the hemoglobin level and rapid reduction in splenic size, with clearance of malarial parasites from the bloodstream. Although reported typically in adult tropical residents, hyper-reactive malarial splenomegaly may occasionally be found in the pediatric traveler. Clinicians receiving children returning from the tropical regions should be aware of this potentially life-threatening complication of partially treated malaria.

Hyperreactive malarial splenomegaly is associated with low levels of antibodies against red blood cell and Plasmodium falciparum derived glycolipids in Yanomami Amerindians from Venezuela

The immunological basis of the aberrant immune response in hyperreactive malarial splenomegaly (HMS) is poorly understood, but believed to be associated with polyclonal B cell activation by an unidentified malaria mitogen, leading to unregulated immunoglobulin and autoantibody production. HMS has been previously reported in Yanomami communities in the Upper Orinoco region of the Venezuelan Amazon. To investigate a possible association between antibody responses against Plasmodium falciparum and uninfected red blood cell (URBC) glycolipids and splenomegaly, a direct comparison of the parasite versus host anti-glycolipid antibody responses was made in an isolated community of this area. The anti-P. falciparum glycolipid (Pfglp) response was IgG3 dominated, whereas the uninfected red blood cell glycolipid (URBCglp) response showed a predominance of IgG1. The levels of IgG1 against Pfglp, and of IgG4 and IgM against URBCglp were significantly higher in women, while the anti-Pfglp or URBCglp IgM levels were inversely correlated with the degree of splenomegaly. Overall, these results suggest differential regulation of anti-parasite and autoreactive responses and that these responses may be linked to the development and evolution of HMS in this population exposed to endemic malaria. The high mortality rates associated with HMS point out that its early diagnosis together with the implementation of malaria control measures in these isolated Amerindian communities are a priority.

Hyper-reactive malarial splenomegaly: rare cause of pyrexia of unknown origin

Hyper-reactive malarial splenomegaly (HMS) or Tropical splenomegaly syndrome(TSS), occurs in areas of high transmission of malaria. These children usually presents with gross splenomegaly and abdominal discomfort, while fever is not the usual manifestation in majority of them. It is a disease of young adults and rarely reported below 8 years of age. Here it is reported a three-year-old child who presented as pyrexia of unknown origin with hepatosplenomegaly, diagnosed as HMS.

The importance of the spleen in malaria

There are several malaria vaccine candidates at various stages of development. Many of these target blood stages of Plasmodium falciparum. The spleen is a key site for removal of parasitized red blood cells, generation of immunity and production of new red blood cells during malaria. This article describes how all of these processes are modified following infection, and suggests that until we fully understand how these processes function and are modulated by infection, appropriate malaria vaccine design and delivery will be extremely difficult to achieve.

The use of PCR in the diagnosis of hyper-reactive malarial splenomegaly (HMS)

Between August 1997 and September 1998, 14 cases of hyper-reactive malarial splenomegaly (HMS) were diagnosed in the Instituto de Salud Carlos III in Madrid, Spain. These cases, from Equatorial Guinea and Cameroon, were identified using the diagnostic criteria established by Y. M. Fakunle in 1981: gross splenomegaly; high levels of anti-malarial antibodies; IgM in serum at least two standard deviations above the local mean; and clinical and immunological response to antimalarial treatment. Although malarial parasites were only detected in the Giemsa-stained blood films of four of the cases, these four and four others were found to have the DNA of such parasites in their blood when tested using a method based on a semi-nested, multiplex PCR. These result indicate that malarial parasitaemias may be more prevalent in HMS than is usually recognized.

Hyperreactive malaria in expatriates returning from sub-Saharan Africa

The extreme presentation of hyperreactive malaria is hyperreactive malarial splenomegaly syndrome (HMS). Some patients present with a less pronounced syndrome. To investigate whether the degree of splenomegaly correlates with the degree of immune stimulation, whether prophylaxis or recent treatment play a role, and whether short therapy alone is effective, we examined retrospectively the medical records of expatriates with exposure to P. falciparum who attended our outpatient department from 1986 to 1997, particularly subacute symptoms or signs, strongly elevated malarial antibodies and elevated total serum IgM. We analysed duration of stay, prophlyaxis intake, spleen size, serum IgM levels and response to antimalarial treatment. Serum IgM levels were significantly higher in patients with larger splenomegaly. The use of chloroquine alone as treatment for presumptive or proved malaria attacks was correlated with larger spleen size. Short adequate antimalarial therapy resulted in marked improvement or complete recovery. In nine patients the hyperreactive response reappeared after re-exposure, in four of them twice. We conclude that patients with subacute symptoms but without gross splenomegaly may have very high levels of IgM and malarial antibodies, and relapse on re-exposure, suggesting the existence of a variant of the hyperreactive malarial splenomegaly syndrome without gross splenomegaly.

[Hyperreactive malarial splenomegaly in a European returning from Africa]

INTRODUCTION

Hyper-reactive malarial splenomegaly (HMS) syndrome related to abnormal immunologic response to repeated malarial infections is unusual in European expatriates.

EXEGESIS

We report the case of a 72-year-old white male patient who had been residing in the Congo and developed a typical clinical features of hyperactive malarial syndrome characterized by massive splenomegaly with hypersplenism, high titers of malarial IgM antibodies, IgM macroglobulinemia, liver and medullary lymphocytic proliferation, and a clinical and immunological response to long-term chloroquine therapy.

CONCLUSION

Criteria for the diagnosis of hyper-reactive malarial splenomegaly are useful. However, making a distinction from malignant lymphoproliferative disorders is difficult, as a sustained response to chloroquine is required. Therefore, chloroquine appears to have a regulatory effect on the immune system.

Use of immunoglobulin gene rearrangements to show clonal lymphoproliferation in hyper-reactive malarial splenomegaly

In Africa, hyper-reactive malarial splenomegaly (HMS), which is also known as tropical splenomegaly syndrome, can be associated with a prominent lymphocytosis in blood and bone marrow that is difficult to distinguish clinically from chronic lymphocytic leukaemia (CLL). The observation that some patients with HMS become resistant to treatment with anti-malarial drugs has led to the suggestion that HMS may evolve into a malignant lymphoproliferative disorder. To test this hypothesis, 22 Ghanaian patients with HMS and/or lymphocytosis were categorised by degree of response to proguanil according to standard clinical criteria, and DNA was extracted from peripheral blood cells and screened for rearrangements of the Jh region of the immunoglobulin gene with a DNA probe. Clonal rearrangements of the Jh region were found in all 3 patients with no response, in none of 13 patients with sustained response, and in 2 of 6 patients with moderate response or relapse on proguanil therapy. The detection of such rearrangements, and hence clonal lymphoproliferation in individuals with clinical features intermediate between HMS and CLL, supports the hypothesis that HMS may evolve into a malignant lymphoproliferative disorder.

Cell surface antibodies in type 1 (insulin-dependent) diabetic patients. II. Presence of immunoglobulins M which bind to lymphocytes

A standardized cell surface antibody assay was used to measure binding of circulating human immunoglobulins to rat or piglet splenocytes. In 100-fold diluted serum fractions, lymphocyte surface antibodies were detected in 30% of Type 1 (insulin-dependent) diabetic patients under 20 years of age but in none of 33 control subjects. Binding occurred with T and B lymphocytes, appeared unrelated to Fc receptors or protein glycosylation and was not attributable to insulin or albumin antibodies. At clinical onset of the disease, the lymphocyte surface antibodies belonged primarily to the IgM-class. Their presence was positively correlated to that of IgM-pituitary cell surface antibodies and their absorption by anterior pituitary cells occurred as well as by splenocytes. Lymphocyte surface antibodies remained present during the first years of insulin treatment. They were also detected in first degree relatives of lymphocyte surface antibody-positive patients. It is unlikely that IgM-lymphocyte surface antibodies mark the destructive process in the pancreatic B cell population. They may, instead, express a state of immune reactivity which precedes the formation of IgG-autoantibodies and therefore be associated with an event in the development of diseases such as Type 1 (insulin-dependent) diabetes.

Immunopathological mechanisms in the induction of parasitic diseases with particular reference to type III hypersensitivity reactions

During the primary immune response to an infectious agent, specific memory cells are generated which enable the immune system to respond more rapidly and efficiently to re-exposure to the same agent. Under normal circumstances, this acquired resistance leads to the effective elimination of the agent, and recovery. However, under certain circumstances these secondary infections, rather than aiding recovery, actually produce tissue damage and often contribute to the disease process. This stage has been termed hypersensitivity and such hypersensitivity reactions play an important role in the immunopathology of several diseases. Coombs & Gell (1963) have classified hypersensitivity into four types of reaction. Types I, II and III involve antibody-mediated processes whereas type IV is mediated solely by lymphocytes. Many parasitic infections have characteristics which would appear to predispose the host to the development of hypersensitivity states and consequent immunopathology. These include (1) the chronicity of the infections, (2) the release of parasite antigens in large amounts and their persistence in the circulation and host tissues, (3) the sharing of antigens between parasite and host and (4) the ability of the parasite to damage host tissues and alter their antigenicity. However, direct evidence that these mechanisms lead to the development of immunopathology in parasitic infections is limited. In this article, these four types of hypersensitivity will be briefly discussed in the context of the immunopathology following parasite infection. There then follows a more extensive consideration of type III hypersensitivity with particular emphasis on the mechanisms underlying the development of immune-complex mediated disease.

Hyperreactive malarious splenomegaly (tropical splenomegaly syndrome)

Hyperreactive malarious splenomegaly (HMS), formerly known as tropical splenomegaly syndrome (TSS), was recognized some 20 years ago as an entity distinct from the splenic enlargement resulting directly from malarial parasitaemia. Its basis appears to be a disturbance in the T-lymphocyte control of the humoral response to recurrent malaria, possibly linked to particular HLA Class II antigens. Gross overproduction of IgM antibodies leads to the formation of high molecular weight immune complexes, persistent gross splenomegaly recurrent episodes of profound anaemia and increased susceptibility to infections. Those with gross disease experience a high mortality, which constitutes a major public health problem in communities where the syndrome affects a majority of adults.