Oue, Yuri, Saiki, Ryosuke, Murata, Tomohiro et al. · Reports (MDPI) · 2026 · DOI
This case report describes a 60-year-old woman who was initially misdiagnosed with chronic fatigue syndrome when she actually had sarcoidosis (an inflammatory disease) affecting her kidneys. Doctors discovered this by finding very high levels of a protein called β2-microglobulin in her urine, which led to a kidney biopsy that confirmed the diagnosis. After treatment with a steroid medication, her kidney function improved and her fatigue completely resolved.
This study is relevant to ME/CFS research because it illustrates how systemic inflammatory conditions like sarcoidosis can mimic or be confused with ME/CFS, potentially leading to diagnostic errors. The case demonstrates the importance of targeted screening for treatable underlying conditions in patients presenting with fatigue and systemic symptoms, highlighting the need for differential diagnosis protocols in ME/CFS clinical practice.
This single case report does not establish how commonly renal sarcoidosis is misdiagnosed as ME/CFS, nor does it prove that urinary β2-microglobulin screening should be routine in all fatigue patients. The dramatic treatment response in one patient does not indicate that similar outcomes would occur in other sarcoidosis cases or that this biomarker is specific or sensitive for detecting renal sarcoidosis broadly.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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