Atypical imported loiasis characterised by recurrent anaemia in a patient from China

Abstract

In March, 2021, a 49-year-old man was admitted to The Fourth People's Hospital of Nanning (Nanning, China) with recurrent dizziness and fatigue that had persisted for more than 1 year. Physical examination revealed paleness on his face and a slightly yellow sclera. He had no hepatomegaly, but he had splenomegaly. His laboratory results showed a low haemoglobin concentration of 84 g/L, a normal blood eosinophil percentage of 3·1%, a high reticulocyte percentage of 4·6%, haemoglobinuria (score of 2+), a low haptoglobin concentration of 1·01 mg/dL (normal range 32–205 mg/dL), a high lactic acid dehydrogenase concentration of 750 U/L (normal range 120–160 U/L), and a high 3-hydroxybutyrate dehydrogenase concentration of 711 U/L (normal range 72–182 U/L). He had a history of haemolytic anaemia, and the lowest haemoglobin concentration recorded was 46 g/L. The patient had previously received four blood transfusions. He had a history of malaria in Ghana and the Democratic Republic of the Congo and thus was tested for malaria. However, microfilariae (an average of 180 per mL) were incidentally discovered on examining peripheral blood samples collected on the day and night of admission. The microfilariae were 225–251 μm long and 6–8 μm wide (figure). A bone marrow smear showed two microfilariae; however, cerebrospinal fluid and urine samples showed no microfilariae. PCR identified a 286 bp filarial-specific internal transcribed spacer 1 (ITS1) fragment and a 712 bp fragment of mitochondrial cytochrome c oxidase subunit 1 (COX1). Analysis with the basic local alignment search tool on the National Center for Biotechnology Information website showed that the ITS1 and COX1 fragments had the highest similarity with those of Loa loa (99% [MK978707] and 95% [HQ186250], respectively). Review of the patient's malaria thick blood smear slide from March, 2020, revealed the presence of two microfilariae, which has not been reported previously. Additionally, in June, 2020, liver fluke eggs in the patient's stool had been reported previously and he had received albendazole (650 mg) twice daily for 7 days. Following the identification of L loa, a diagnosis of atypical imported loiasis was established and the patient was treated at our hospital with a single dose of ivermectin (150 μg/kg) orally for anti-filariasis treatment, without intervention for anaemia. 2 weeks after treatment, a peripheral blood smear showed that the number of microfilariae had decreased to nine per mL on average, and his haemoglobin concentration had increased to 120 g/L and his eosinophil percentage had increased to 22·1%. 6 weeks after treatment, his haemoglobin concentration had increased to 147 g/L, with no microfilariae detected in his peripheral blood, suggesting that his anaemia was caused by filariasis.