Acute myeloid leukemia with microfilaria: An uncommon finding

INTRODUCTION

Over 15 million people have lymphedema, and 25 million males globally are thought to have hydrocele, according to the WHO’s baseline estimate of lymphatic filariasis incidence.^[1] On the other hand, acute myeloid leukemia (AML) makes up 23.1% of all leukemia cases globally. In India, filariasis is widespread and might manifest as elephantiasis, lymphadenopathy, or pyrexia. Microfilariae have been found incidentally in cytological preparations from a wide range of locales, including bone marrow aspirates.^[2,3] The literature has, however, hardly ever reported the appearance of microfilariae in bone marrow aspirates or peripheral smears in conjunction with a hematological malignancy.^[4]

In this case, we report a 63-year-old woman with AML whose peripheral blood and bone marrow smears showed microfilariae.

CASE REPORT

A 63-year-old female presented with chief complaints of fever for 20 days, generalized body rash for 5 days associated with blood in stool and hematemesis, one episode each, and gum hyperplasia associated with dysphagia. On examination, pallor and hepatosplenomegaly were appreciated. She had right upper cervical lymphadenopathy. Her complete blood count findings showed red blood cell count of 2.2 million/cumm, hemoglobin 5.6 g/dL, total leukocyte count markedly increased to 1,97,180/µL, and platelet count reduced to 26,000/µL. Peripheral blood smears show 60% blasts. Bone marrow examination shows particulate hypercellular marrow with 83% blasts. Blasts are large, with moderate to abundant cytoplasm and open chromatin; 2–3 prominent nucleoli resembling myeloblasts, with irregular nuclear contours. Some of the blasts showed cytoplasmic Auer rods and granules. Sudan Black-B is positive for blasts. Peripheral blood smear and bone marrow smears also show sheathed microfilariae with a somatic nucleus not reaching up to the tail end, suggesting it to be Wuchereria bancrofti microfilariae [Figures 1-3]. Not associated with clinical manifestations of filariasis, such as eosinophilia. A final diagnosis of AML with microfilariae was put forth.

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Figure 1:

Peripheral blood smear showing sheathed microfilariae with blasts adjacent to it (magnification ×100, Leishman stain).

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Figure 2:

Bone marrow smear showing the microfilariae. (magnification ×100, Leishman stain).

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Figure 3:

Bone marrow aspirate smears showing the microfilariae with blasts population (magnification ×400, Leishman stain).

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DISCUSSION

The association between microfilariae and leukemia is quite rare. To the best of our knowledge, only a few cases have been documented in the literature thus far. Since there were no symptoms associated with this parasitic infection, the discovery of microfilariae in this case was purely accidental. Leukemia patients’ impaired immune systems have been proposed as a risk factor for parasite infections. However, this might be an accidental discovery in a nation like ours, where filariasis is endemic in some areas. It could be linked to any illness. Microfilaria can occasionally be detected in bone marrow or peripheral smears, even when they are not clinically suspected.^[5]

After being laid at the puncture site, the larvae gradually make their way through the epidermis and enter the lymphatic pathways before settling in nearby lymph nodes. There, they develop over 5–18 months, giving birth to new larvae that pass through the thoracic duct and reach the pulmonary capillaries, the venous system, and the peripheral circulation. As a result, they can enter the bone marrow or any other area of the cardiovascular system. On the other hand, microfilaria in bone marrow aspirate is unusual and rare.^[5]

More recent diagnostic techniques have been developed, such as the simple circulating filarial antigen assays. Eosinophil blood counts are frequently used as screening tools for filariasis, which causes acquired eosinophilia. However, microscopy is still the primary method of diagnosis. The sensitivity of light microscopy can be increased by concentrating samples, using centrifugation, or filtering through Millipore membrane filters. The labor-intensive nature of making and inspecting microscope slides is a drawback. The amount of blood sampled, the time of blood collection, and the potential for bias introduced by pathologists’ expertise and commitment all affect the sensitivity with which microfilariae are detected. Unfortunately, in both the early and late stages of the disease, microfilariae are often absent from the blood.^[6] Many infections cannot be detected by microscopy because of its limited sensitivity, particularly those with low densities and those in which adult worms are present but do not form microfilariae. The sensitivity of serological testing is insufficient. It does not distinguish between infections from the past and those from the present. For the detection of W. bancrofti, both conventional and real-time polymerase chain reactions have been devised; however, most centers do not regularly perform these tests.^[7]

In India, asymptomatic microfilaremia is rather prevalent. The traditional clinical appearance was absent from our instance. By identifying microfilariae in peripheral blood and bone marrow smear, filariasis was diagnosed.

CONCLUSION

Microfilaria with AML coexisting is a rare and unusual finding. AML is a hematologic cancer, whereas microfilaria is a parasitic infection commonly encountered in tropical regions. When several illnesses occur simultaneously, overlapping symptoms may make diagnosis and treatment more difficult. When examining patients, professionals must consider both possibilities, particularly in endemic areas, to ensure an accurate diagnosis and appropriate treatment for both the parasitic infection and leukemia.