A Pilot Analysis of Bioparameters in Patients with Dyspepsia Accompanied by Abdominal Hardness: An Exploration of Damjeok Syndrome Rooted in Traditional Medicine

<b>Background</b>: A subset of patients with chronic dyspepsia exhibits palpable upper abdominal hardness and systemic symptoms like headache, chest discomfort, neck/shoulder stiffness, fatigue, and depression. In traditional Korean medicine (TKM), this symptom complex is referred to as <i>Damjeok</i> syndrome (, DJS). Although DJS is frequently observed in TKM practice, it lacks a clear case definition and biological mechanism, limiting its integration in gastroenterology research and evidence-based practice. Clarifying its clinical and biological features is essential to understand its pathophysiology and clinical significance. <b>Methods</b>: This case-control study aimed to characterize DJS by comparing 16 female patients diagnosed with DJS and 15 age-matched healthy females as controls. A female-only cohort was selected to reflect the higher prevalence of chronic dyspepsia in women and reduce biological variability. Clinical characteristics and potential DJS-specific biomarkers were evaluated through complete blood count (CBC), serum biochemical tests, heart rate variability (HRV) for autonomic function, and plasma 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite linked to gastrointestinal motility and autonomic regulation. <b>Results</b>: The DJS group had a mean disease duration of 58.0 ± 46.2 months, with epigastric fullness and underlying abdominal hardness as primary complaints. Postprandial distress syndrome (PDS) was the most common (43.8%) dyspepsia subtype, often combined with epigastric pain syndrome (EPS). Extra-gastrointestinal symptoms such as headache/fatigue (87.5%) and anxiety/depression (81.3%) were highly prevalent. Neutrophil counts were significantly lower in the DJS group (<i>p</i> = 0.01), while other hematological or biochemical markers showed no differences (<i>p</i> > 0.1). HRV analysis revealed decreased parasympathetic activity (RMSSD and HF, <i>p</i> < 0.1), and plasma 5-HIAA levels were significantly elevated compared to healthy controls (<i>p</i> = 0.01). <b>Conclusions</b>: DJS aligns with functional gastrointestinal disorders (FGIDs), sharing psychosomatic symptoms and reduced parasympathetic activity, suggesting gut-brain axis dysregulation. However, distinct features like palpable upper abdominal hardness and elevated plasma 5-HIAA levels indicate that DJS may represent a unique subtype within the category of FGIDs. These findings highlight the need for larger, well-designed studies to further elucidate the pathophysiology of DJS.