Incidental radiological finding of pentastomiasis

Description

A man in his 50s presented to the emergency department with melaena and syncope. There was a medical history of psychosis, treated with olanzapine, but no other comorbidity. He was a former smoker and did not drink alcohol. He was born in Central Africa, moving to the UK as a young adult.

On examination, there was no abdominal mass or peritonism. Blood pressure was 116/58 mm Hg and pulse 88 beats per minute. Haemoglobin was 102 g/L and urea 12.2 mmol/L. Acute upper gastrointestinal haemorrhage was suspected.

At gastroscopy, a 20-mm acute gastric antral ulcer was identified with a visible vessel in the base. Rapid urease test was positive for Helicobacter pylori. The ulcer was injected with 10 mL 1:100 000 epinephrine and the vessel clipped endoscopically.

Erect chest X-ray (CXR) was obtained prior to gastroscopy to look for evidence of pneumoperitoneum. CXR showed distension of the stomach, prompting an abdominal X-ray (AXR) to rule out bowel obstruction, which disclosed the incidental finding of numerous small dense curvilinear lesions projected over the abdomen (figure 1).

Figure 1.

Abdominal X-ray.

CT scanning of the abdomen and pelvis was arranged to characterise AXR findings, demonstrating small calcific foci throughout the mesentery and liver with no muscle deposits (figure 2). Subsequent CT thorax and brain showed no further lesions.

Figure 2.

Coronal CT image of the abdomen and pelvis.

The distribution of curvilinear calcified foci within the mesentery and liver is characteristic of pentastomiasis.^{1 2} Absence of deposits in muscle, thorax or brain makes the differential diagnosis of cysticercosis unlikely.³

Pentastomiasis is a parasitic disease caused by arthropods of Armillifer species, found in the respiratory system of the snake.¹ Most cases occur in people from West Africa and Central Africa who consume snakes as part of their diet.³ Parasite load is usually low and subjects are generally asymptomatic with no specific treatment required. Encapsulated larvae typically die within 2 years and become calcified: pentastomiasis is most often identified when these lesions are incidentally encountered at laparotomy or on radiological examination, and may be detected many years after the initial infection.^{2 4}

The life cycle of Armillifer species is explained in figure 3. Mature adult Armillifer pentastomes mainly reside in the respiratory system of the final host (large snakes) which may infect humans who consume uncooked snake meat as part of their diet.⁵

Figure 3.

Life cycle of Armillifer species. (Figure created by Danielle Tang.)

In light of imaging results, further history from the patient was obtained. He had regularly killed and eaten snakes while resident in Central Africa, confirming the risk factor for historical infection with Armillifer.

The patient made a good recovery from peptic ulcer disease with H. pylori eradication and acid suppression. Follow-up gastroscopy at 6 weeks confirmed ulcer healing. He was reassured that no further action was required regarding the diagnosis of pentastomiasis.

Learning points.

• Differential diagnoses of curvilinear calcific deposits on abdominal X-ray in a patient with relevant travel or residential history include cysticercosis and pentastomiasis.

• Radiological distribution of calcific deposits facilitates discrimination between these possibilities: cysticercosis is characteristically present in the muscle, thorax and brain, while pentastomiasis is usually confined to the mesentry and liver.

• Individuals who include snakes in their diet should be advised to cook the meat thoroughly prior to consumption to reduce the risk of pentastomiasis.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).