Growing Eye Mass Leads to a Rare Diagnosis

What caused a healthy 28-year-old woman to develop a gradually expanding mass in the inside corner of her left eye? That’s what Grégoire Van Acker, MD, of Cliniques Universitaires Saint-Luc in Brussels, and colleagues needed to figure out when she presented for care.

The patient explained that she had been on a humanitarian mission in the Democratic Republic of Congo. The lump had appeared 2 years ago and gradually increased in size since then, they reported in JAMA Ophthalmology.

On taking the patient’s history, clinicians learned that she had never had an eye injury nor had experienced any other symptoms.

She denied ever eating or having contact with snakes. However, she regularly ate crocodile meat as part of her regular diet.

A physical examination revealed a subconjunctival foreign body in the inner canthus of the eye. It was not fixed in place but did not show spontaneous movement. There was no evidence of inflammation present in the anterior chamber. Findings of the rest of the physical were unsurprising, they noted.

The team performed a conjunctival incision, which revealed a 10-mm C-shaped larva, with several annulations. They extracted the larva and the specimen remained immobilized following its removal.

The larva, along with its surrounding exuvia (transparent cuticle), was placed in 70% ethanol solution and shipped to the National Reference Center of Tropical Pathogens in Germany for testing. The lab used polymerase chain reaction (PCR) primers targeting the nuclear 18S RNA gene of the pentastomid. After sequencing, the specimen was identified as Armillifer grandis.

Discussion

“Pentastomiasis is a rare zoonotic disease caused by the larval stages of pentastomid parasites,” noted Van Acker and co-authors. In humans, the infection generally occurs in those living or travelling in the tropics and subtropics.

Pentastomiasis infection affecting the eye is particularly rare, and this patient’s case may be the first such report published in an ophthalmologic journal, according to the case authors.

Among the pentastomids that can infect humans, characteristics such as species and hosts vary by geographical location.

“In Africa and Asia, the disease is often caused by Armillifer species, which have snakes as their final host, whereas Linguatula infections are cosmopolitan, with dogs as final hosts,” Van Acker and colleagues explained.

Pentastomiasis infections frequently involve the viscera and often remain undiagnosed, since most people with the disease remain asymptomatic. However, “symptoms may develop when the larvae grow, migrate, perforate organs, or die, causing a strong immune reaction,” they noted.

In the rare instances when pentastomiasis affects the eye, it tends to cause significant symptoms, although there are very few descriptions of eyelid, subconjunctival, or intraocular infections. However, ocular infections due to Armillifer grandis have been described in the Democratic Republic of Congo, specifically in the Sankuru district, the authors noted.

This patient’s case may be the first reported occurrence of Armillifer ocular infection associated with consumption of crocodile meat. Crocodiles can be infected by pentastomids, or the meat could have been contaminated by contact with infected snake meat in a market stall.

Van Acker and co-authors said that of the various possible treatments that clinicians may consider, surgical removal of the larvae is the treatment of choice. Use of antiparasitic medication is not ideal, because “the dying larvae may release an antigen capable of inducing a strong immune response,” they explained.

Prevention involves mainly hygienic measures. In particular, the following factors often associated with Armillifer infections should be avoided:

Close contact with parasitized snake hostsConsumption of undercooked reptile meatIngestion of food or water potentially contaminated with snake feces or pentastomid eggs

Currently, there is no serological test available, and morphological criteria and/or histopathology findings are used to make the final diagnosis. “PCR tests targeting the parasite’s 18S rRNA gene and mitochondrial cytochrome oxidase subunit genes are reliable diagnostic methods,” the authors said. However, in rural endemic regions with few high-resource laboratories, these are often difficult to access.

Despite the rarity of ocular pentastomiasis, Van Acker’s group said that “ophthalmologists should consider the diagnosis in patients coming from endemic countries. Higher awareness for this rare but sometimes heavily symptomatic disease seems warranted.”