Intestinal permeability correlated with chronic fatigue in a patient with long COVID—A case report and overview of the literature

Background Long COVID is a complex condition characterized by persistent symptoms such as chronic fatigue, cognitive impairment, and autonomic dysfunction. Emerging evidence suggests that the gut may play a role in the pathophysiology of long COVID, potentially contributing to systemic inflammation and symptom severity. Prior studies indicate intestinal permeability (IP) alteration in patients with long COVID. To date, there have been no reports on the assessment of intestinal permeability via carbohydrate absorption in individuals with long COVID. Case presentation We present a 60-year-old female with long COVID who exhibited chronic fatigue and autonomic dysfunction for more than 3 years following SARS-CoV-2 infection. IP was assessed at five time points using a carbohydrate absorption test. Results revealed significantly elevated lactulose/mannitol (L/M) ratios during episodes of symptom exacerbation, including a second SARS-CoV-2 infection. Notably, clinically observed improvement in fatigue correlated with a reduction in IP. A probiotic regimen with Bacillus coagulans and Bacillus subtilis , combined with a second intervention using medicinal clay, led to further clinical improvement. Conclusions This case report demonstrates a correlation between intestinal permeability alterations and long COVID symptom severity. Notably, to our knowledge, this is the first report assessing intestinal permeability in a long COVID patient using a carbohydrate absorption–based permeability test. It reinforces the emerging link between gut barrier integrity and long COVID pathophysiology and emphasizes the need for further studies to assess IP as a potential disease marker. Furthermore, the observed improvement with probiotic therapy highlights the need for further research into microbiome-targeted interventions for long COVID management. Larger studies are required to explore the mechanistic link between gut permeability and long COVID pathophysiology.