The diagnostic conundrum of hyper eosinophilia—Sheer tenacity of a parasite

We present an interesting and rare case of Capillaria hepatica infection in a 2-year-old boy, who presented with fever, rash, hepatomegaly and peripheral eosinophilia. FNAC of hepatic lesion showed parasitic eggs and PCR from the aspirate confirmed the diagnosis. We describe the cytomorphological features and provide educational multiple-choice questions related to the topic. A 2-year-old boy presented with chief concerns of chronic rash over cheeks for 2 months and high-grade fever for 15 days. There was a significant history of pica. On examination, there was an erythematous rash extending over bilateral maxillary eminence, studded with papular lesions with a dry, scaly appearance and firm, non-tender hepatomegaly. Laboratory investigations revealed microcytic hypochromic anaemia with severe peripheral eosinophilia (28 × 109cells/L). Evaluation of eosinophilia, including multiple stool examinations for atypical ova and cysts, serologies for toxocara, toxoplasma, amoebiasis, strongyloidiasis, filaria, and trichinella were negative. Ultrasound abdomen revealed multiple hypoechoic lesions in the liver, largest measuring 1.1 × 0.8 cm in segment IVa, likely granulomatous aetiology (Figure 1). FNAC was done from the hepatic lesion; the smears were prepared and the aspirate was also sent for mycobacterial culture and for polymerase chain reaction (PCR) to identify parasitic infection. The smears revealed clusters of benign hepatocytes, numerous eosinophils, occasional epithelioid cell collections, crushed stromal fragments, and proliferating bile ductular channels. In addition, a few scattered parasitic eggs of approximate size of 60 μm length and 35 μm width were seen (Figure 2). The eggs were barrel-shaped with double-layered shell with striated outer shell (Figure 2E) and polar plugs on both ends. PCRs for filaria, dirofilarial, tricuris and Strongyloides were negative, however PCR for Capillaria hepatica was positive (Figure 3). The child improved clinically on a course of albendazole. Liver is a prime target for many parasites, which may either reside in the organ, transit through it during their lifecycle, or be transported to it, resulting in hepatic damage.1 Hyper-eosinophilia may signal an underlying parasitic infection especially Capillaria hepatica, Fasciola hepatica, or Trichuris. Capillaria hepatica is a nematode primarily affecting the liver of wild rodents. After ingestion of embryonated eggs, larvae hatch in the intestine and reach the liver where they mature into adults. Females lay unembryonated eggs which become encapsulated, and these further reach the environment through the decay of the host's carcass after death or through the shedding of eggs in the faeces leading to 'Spurious infection' (AQ1). Ingestion of embryonated eggs through contaminated food in humans or because of geophagia results in secondary infection in humans.2 Once inside the host, the larvae migrate to the liver, causing significant hepatic damage and leading to eosinophilia. Gold standard for diagnosis is liver biopsy which shows eggs of C. hepatica, which are barrel-shaped, bioperculated and measure approximately 55–65 μm in length and 29–33 μm in width.3 The eggs have a thick, double-layered shell with polar plugs at both ends, which is a distinctive feature. The outer shell is often striated or ridged (AQ2). Inside the egg, a single cell or developing embryo can be seen, depending on the stage of development.4 The eggs of C. hepatica are similar in size to eggs of Trichuris trichiura (whipworm), which are 50–55 μm in length, 22–23 μm in width (AQ3), barrel-shaped and have a prominent bipolar appearance. However, eggs of Fasciola hepatica are larger and oval, measuring about 130–150 micrometres in length and 60–90 micrometres in width (AQ4). FNAC of hepatic lesions plays a pivotal role in identifying rare parasitic infections. Properly triaging the aspirate is crucial to enable ancillary techniques like PCR, ensuring a timely diagnosis and management. AP, RA and AA: Data collection and interpretation, Initial draft of the manuscript and approval of the final version of the manuscript. NG: Conceptualization, data interpretation, formal analysis, supervision, validation, visualization, writing, review and approval of the final version of the manuscript. SK: Data interpretation, formal analysis, visualization, review, editing and approval of the final version of the manuscript. AG, AS: Data collection, data interpretation, clinical patient management, manuscript review, editing and approval of the final version of the manuscript. None. None. Not available.