Letter to the Editor: Blastocystis hominis in Acute Pancreatitis: Innocent Bystander or Pathogen?

To the Editor:

B lastocystis hominis is a protozoan commonly found in the human gastrointestinal tract. Blastocystis hominis colonizes many individuals, but pathogenicity is determined by the interaction between its virulence and host immune response. Blastocystis hominis infection can cause abdominal symptoms and cutaneous disorders [1]. However, there is an ongoing controversy about how Blastocystis hominis should be treated in symptomatic patients, if at all, because symptoms could be caused by other pathology. We report a patient with infected pancreatic necrosis (IPN) and Blastocystis hominis infection. We decided to treat Blastocystis hominis infection because of the possibility of immune compromise from IPN.

A 38-year-old male was admitted with one day of generalized abdominal pain associated with vomiting. He had no past medical history and did not drink alcohol. Serum investigations revealed a normal lipid profile, normal calcium, deranged liver function test, and elevated amylase. A clinical diagnosis of acute gallstone pancreatitis was made. Abdominal imaging on the fifth day confirmed necrotizing pancreatitis. Because of hemodynamic instability and suspected IPN, percutaneous retroperitoneal drainage was performed. Fluid grew Klebsiella pneumoniae, sensitive to amoxicillin-clavulanate. The patient developed watery diarrhea that was attributed to being a side effect of amoxicillin-clavulanate. However, because of IPN, a stool sample was taken. Blastocystis hominis was detected in stool samples. Amoxicillin-clavulanate was continued, and metronidazole was added. The patient improved, and the percutaneous drain was removed after few weeks.

Blastocystis hominis is an anaerobic parasite that is considered both a commensal as well as a pathobiont. It is detected more commonly in fecal samples of patients residing in hot and humid climates and of lower socioeconomic stratus [1]. Amin et al. [2] reported that Blastocystis hominis accounted for 23% of intestinal parasitic infestations. Our patient was a migrant worker from a developing country. Blastocystis hominis, when symptomatic, presents with typical gastrointestinal symptoms, including abdominal pain and diarrhea, followed by non-specific symptoms of nausea, anorexia, bloating, and flatulence [1]. Occasionally, Blastocystis hominis can cause urticaria [1]. Many authors report that the presence of Blastocystis hominis in stool samples from patients showing gastrointestinal symptoms does not necessarily imply that symptoms are caused by this organism, and other infective and non-infective causes should be investigated. A retrospective study by Kuo et al. [3] that included 100 patients with positive Blastocystis hominis cultures found that all had other conditions that could explain their presenting complaints, and all patients improved without treatment for Blastocystis hominis. Our patient developed diarrhea after starting antibiotic therapy, and thus our primary consideration was antibiotic-associated diarrhea. However, it is also reported that in immunocompromised patients, Blastocystis hominis infection could be pathogenic, and thus eradication therapy should be considered. Blastocystis hominis infection is reported in patients with acquired immune deficiency syndrome [4]. A double-blind, randomized controlled trial by Rossignol et al. [5] including 84 patients found that in 86% of patients with culture-positive Blastocystis hominis symptoms resolved after four days of nitazoxanide therapy.

In conclusion, Blastocystis hominis infection is common. In most patients, Blastocystis hominis is an “innocent bystander” rather than a pathogen. However, in patients with possible immunocompromise, eradication treatment may be prudent.