Blastocystis hominis infection inducing gut microbiome dysbiosis and aggravating Parkinson's disease symptoms: a case report.

backgroundBlastocystis hominis infection in patients with Parkinson's disease may exacerbate gut microbiota dysbiosis, potentially worsening neurological symptoms; however, such associations remain speculative without microbiome data. Targeted interventions to restore gut microbial balance could mitigate disease progression and improve patient outcomes. CASE PRESENTATION: An 86-year-old Caucasian male presented to the emergency department with severe watery diarrhea, up to six episodes per day, of 1 month duration. The patient's diarrhea was nonbloody and nonmucoid. He denied fever, nausea, vomiting, abdominal pain, bloating, loss of appetite, or anal itching. There was no history of weight loss, fatigue, or systemic symptoms. A stool sample was examined microscopically using normal saline, revealing Blastocystis hominis cysts (the burden was not quantified) and a rare white blood cell count. The sample was concentrated using acetylacetate and ether. Additional tests, including Clostridioides difficile and other common infectious pathogens, were ruled out in our patient to address alternative infectious etiologies.The patient was started on intravenous ciprofloxacin and metronidazole, resulting in an improvement in diarrhea consistency and frequency until the resolution of symptoms within 4 days of initiating intravenous therapy. The patient also reported mild improvement in his Parkinson's disease symptoms by the end of hospitalization, though objective neurologic post-treatment scoring (eg. Unified Parkinson's Disease Rating Scale) was not performed.

conclusionThis case highlights the need to consider parasitic infections in patients with Parkinson's disease presenting with chronic diarrhea. While we hypothesize that B. hominis infection may transiently worsen Parkinson's disease symptoms through inflammatory or microbiota-mediated pathways, this remains speculative in the absence of microbiome sequencing or objective neurologic evaluation. Further studies integrating clinical, microbiological, and microbiome analyses are warranted.