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Q1: WHAT IS THE FINDING ON SLIDE OF BONE MARROW EXAMINATION (FIG 1; SEE 300)?
The bone marrow aspiration smear shows microfilariae of Wuchereria bancrofti. The microfilariae (embryos) are usually found in the blood of infected patients. They have sheathed, transparent bodies 290 μm in length and 6–7 μm in width. They have a hyaline sheath and central column of nuclei, which do not extend up to the tail.
Q2: WHAT ARE THE CAUSES OF PANCYTOPENIA?
Pancytopenia is the simultaneous presence of anaemia, leucopenia, and thrombocytopenia. Pancytopenia therefore exists in adults when haemoglobin concentration is less than 135 g/l in males or 115g/l in females, the leucocyte count is less then 4 × 109/l, and platelet count is less than 150 × 109/l. Presenting symptoms are usually due to anaemia or thrombocytopenia. Leucopenia is an uncommon cause of the initial presentation in the patients.
Causes of pancytopenia
(A) Pancytopenia with hypocellular bone marrow
Acquired aplastic anaemia.
Inherited aplastic anaemia (Fanconi's anaemia).
(B) Pancytopenia with cellular bone marrow
1: Primary bone marrow diseases
Paroxysmal nocturnal haemoglobinuria.
Bone marrow lymphoma.
Hairy cell leukaemia.
2: Secondary to systemic diseases
Systemic lupus erthymatosus.
B12, folate deficiency.
Q3: HOW WILL YOU TREAT THIS PATIENT?
The drug of choice for treatment of filariasis is diethylcarbamazine. It is effective in killing microfilariae. The effect of the drug on adult worms is uncertain. The dose of diethylcarbamazine used for treatment of bancroftian filariasis is 6 mg/kg body weight per day orally for 12 days given preferably in divided doses after meals. Diethylcarbamazine may produce severe side effects: (A) those caused by the drug itself—for example, headache, nausea, vomiting, and dizziness. These are observed a few hours after the first dose of diethylcarbamazine and generally do not last for more than three days. (B) Allergic reactions due to destruction of the microfilariae and adult worms—for example, fever, orchitis, lymphadenitis, transient lymph oedema, and hydrocele. The local reactions tend to occur later in the course of treatment and last longer. If the drug is given in divided doses, the systemic reaction is much less severe and less frequent after the second dose and rare after subsequent doses. These reactions disappear spontaneously and rarely require interruption of treatment.
Ivermectin—It is a semisynthetic macrolide antibiotic with activity against various nematodes and ectoparasites. It causes a gradual decrease in microfilariae level over 2–4 weeks to 15%–20% of the pretreatment values. However these low levels are sustained for at least six months after treatment. Maximum effectiveness is seen at the higher dosage of 200 and 400 μg/kg body weight.
Albendazole—400 mg twice daily for 21 days also has macrofilaricidal efficacy.
Two types of filarial infection—that is, W bancrofti and Brugia malayi, occur in India. Out of these two, bancroftian filariasis is responsible for 98% of infection. Man is the definitive host and the mosquito the intermediate host of bancroftian and burgian filariasis.1 The adult worm is found in the lymphatic system, skin, and serous membranes of man. The males are about 40 mm long and females 50–100 mm long. Females give birth to as many as 50 000 microfilariae per day, which find their way into blood circulation via the lymphatic system. The lifespan of microfilariae is not known exactly, but is probably up to a year or more. The adult worms live in the afferent lymphatic or sinuses of lymph nodes for years and causes lymphatic dilatation and thickening of the vessel walls. A lymphatic vessel remains patent as long as the worm remains viable and death of the worm leads to enhanced granulomatous reaction and fibrosis resulting in lymphatic obstruction. The manifestations of filariasis are due to both the direct effects of worms and the immune response of the host to the parasite. Classical disease manifestations can be divided into two distinct clinical types: (A) lymphatic filariasis caused by parasites in the lymphatic system and (B) occult filariasis caused by immune hyper-responsiveness of the human host (for example, tropical pulmonary eosinophilia). The most common presentations of lymphatic filariasis are asymptomatic microfilaraemia, acute adenolymphangitis, and chronic lymphatic disease. The chronic obstructive lesion may present as hydrocele, elephantiasis, and chyluria.1, 2 Rarely chylous arthritis,3 filarial pleural effusion,4 glomerulonephritis,5 and breast lump6 have been described. Our patient manifested the disease as pancytopenia due to the involvement of bone marrow. Until now bone marrow filariasis has not been described. It is possible that liberation of some toxic metabolites by growing larvae—that is, microfilariae, might have caused toxic suppression of the bone marrow. The patient was given diethylcarbamazine and two whole blood transfusions. The patient started improving after a week of treatment. The haemoglobin value rose to 70 g/l. The peripheral blood smear examination showed considerable improvement in total leucocyte and platelet counts. Bone marrow examination repeated after two weeks showed responsive bone marrow and degenerated microfilariae. However, since this is the first case report of bone marrow filariasis, the exact mechanism of bone marrow invasion and suppression needs further elucidation.
Filarial infection mediated toxic depression of bone marrow.