A case of mosquito hypersensitivity terminating as malignant histiocytosis

Epstein-Barr Virus-Infected Malignant T/NK-Cell Lymphoma in a Patient with Hypersensitivity to Mosquito Bites

We report an autopsy case of Epstein-Barr virus (EBV)-infected malignant lymphoma in a young male who had hypersensitivity to mosquito bites. The autopsy revealed multiple confluent lymphoma lesions in the lungs, and on the right leg irregular-shaped skin ulcers were seen. The left pleural effusion also contained a large number of lymphoma cells. The lymphoma cells were determined as T/NK-cell type cells by immunohistochemistry. EBV DNA was detected most intensively in the lungs and EBV-encoded small RNAs-positive lymphoma cells were also observed in the lungs at a high frequency. EBV latent membrane protein-1 expression and a high Ki-67 labeling indices were noted in the lymphoma cells of the lung lesions. These findings indicate that the development of the malignant lymphoma was associated with the proliferation of EBV-infected lymphoma cells, and the cells that infiltrated the whole the body, especially the lungs, caused the patient's death.

Hypersensitivity to mosquito bites as the primary clinical manifestation of a juvenile type of Epstein-Barr virus-associated natural killer cell leukemia/lymphoma

Hypersensitivity to mosquito bites or mosquito allergy is a mysterious disorder that has been reported mainly in Japanese patients (at least 58 patients) in the first two decades of life. The skin lesion at bite sites is typically a bulla that develops into necrosis. Patients simultaneously exhibit a high temperature and general malaise and subsequently may experience lymphadenopathy and hepatosplenomegaly. Recent studies have revealed that this mosquito hypersensitivity is associated with chronic Epstein-Barr virus infection and natural killer cell leukemia/lymphoma. The natural killer cell, infected with monoclonal (or oligoclonal) Epstein-Barr virus, seems to be involved in the pathogenesis of the hypersensitivity. Half of the patients reported died of hemophagocytic syndrome (or malignant histiocytosis), granular lymphocyte proliferative disorder, or lymphomas. We propose that this disease, defined as the triad of hypersensitivity to mosquito bites, chronic Epstein-Barr virus infection, and natural killer cell leukemia/lymphoma, is a clinical entity mostly seen in Asians.

Characterization and sensitivity to interleukin 2 and interferon alpha of leukemic cells from a patient with large granular lymphocytic leukemia associated with chronic active Epstein-Barr virus infection

A patient presented with chronic large granular lymphocyte leukemia associated with chronic active Epstein-Barr virus infection (CAEBV). Cell cycle analysis revealed a minimal growth compatible with chronic lymphocytic leukemia After 5 months of treatment, the patient died from acute transformation of the leukemia. Cell harvested during chronic phase were analyzed for sensitivity to interleukin 2 (IL-2) and interferon alpha (IFN alpha) in vitro by means of surface phenotyping and cell cycle assay. IL-2 induced remarkable growth of the cells, whereas IFN alpha did not confer a growth advantage. Since IFN alpha was expected to have no growth induction effect on the leukemia cells, it was administered to the patient to treat the CAEBV.

Hypersensitivity to mosquito bites conceals clonal lymphoproliferation of Epstein-Barr viral DNA-positive natural killer cells

In order to clarify the relationship between Epstein-Barr (EB) virus and hypersensitivity to mosquito bites (HMB), and to search for the mechanism which induces EB virus-associated lymphoproliferative diseases, we investigated patients with HMB, using hematological, immunological and virological techniques. Among 5 cases of HMB, CD56+ cells had proliferated and CD3+ cells were diminished in 4 cases. Although anti-EB virus antibody titers were not consistent with chronic active EB virus infection, EB viral DNA was detected in the peripheral blood mononuclear cells in all 5 cases. Moreover, EB viral DNA-positive cells had proliferated monoclonally in 4 cases, and biclonally in 1 case. It was proved that most of the EB viral DNA existed in natural killer (NK) cells through polymerase chain reaction analysis. These findings suggest that the basis of HMB may be clonal lymphoproliferation of EB viral DNA-positive NK cells and this hematological abnormality may induce the characteristic symptoms of HMB. In some cases, the proliferating NK cells can metamorphose into leukemic cells, and hemophagocytic syndrome, which has been assumed to be a complication of HMB, may then occur.

A quantitative study of specific immunoglobulins to mosquito salivary gland antigen in hypersensitive and common types of mosquito bite reaction

This study was designed with two purposes: first, to elucidate immunologic mechanisms in different cutaneous reactions, particularly in hypersensitivity to mosquito bites, and, second, to develop a more reliable and safer method of identifying the causative species of mosquito in severe cases. The amounts of IgG, IgG4 and IgE specific to the mosquito salivary gland extract of Aedes albopictus were determined in the sera of 116 volunteers with normal reactions, either immediate or delayed, and 4 patients with severe systemic symptoms caused by mosquito bites. Titers of IgG and IgE in the severe cases were considerably higher than in volunteers with normal reactions, but there were no differences in IgG4 titers between the two groups. These results indicate that high titers of IgG and IgE may be involved in development of systemic symptoms in severe cases and verify the possibility of in vitro tests to identify causative species of the mosquito.

Immunology and treatment of mosquito bites

Cutaneous reactions to mosquito bites are usually pruritic weals and delayed papules. Arthus-type local and systemic symptoms can also occur but anaphylactic reactions are very rare. Both clinical and experimental evidence suggest that the various bite reactions result from sensitization to the mosquito saliva injected into the skin during feeding. Recent immunoblot studies have shown both IgG- and IgE-class anti-mosquito antibodies, but their species-specificity and clinical importance is at present unknown. In addition to an Arthus-type mechanism, both cutaneous late-phase reactivity and cell-mediated immunity may be involved in the pathophysiology of delayed mosquito-bite lesions. Cutaneous sensitization to mosquito bites can be divided into five different stages ranging from the stages of immediate wealing and delayed bite papules, to the stage of non-reactivity. No desensitization treatment is generally available for mosquito allergy but it has recently been shown that cetirizine, a potent non-sedating antihistamine, is effective against the wealing and pruritus caused by mosquito bites.