Introduction
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative virus of coronavirus disease (COVID-19), which was discovered in China in December 2019 (1). To date, there is no end in sight to the disease. The recognized acute phase symptoms of COVID-19 are fever, dyspnea, cough, dysgeusia, and anosmia. Recent attention has focused on COVID-19 sequelae called “long COVID” or post-COVID-19 syndrome (2). After recovery from COVID-19, approximately 50% of patients reportedly experience sleep disturbance and chronic fatigue (3), and approximately 25% meet the diagnostic criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) (4). ME/CFS causes various symptoms such as morbid fatigue, pain, and mental disorders that worsen after exertion; however, its pathogenesis and treatment remain unclear (5). Thus, as many as 80% of patients struggle to receive a diagnosis of ME/CFS, and, in some cases, are forced to consult several specialists and medical facilities for a diagnosis (6).
Currently, there are no blood tests or imaging studies that provide a definitive diagnosis of ME/CFS, although such procedures may serve to rule out alternative competing diagnoses. However, of the clinical symptoms and laboratory tests commonly regarded as suggestive of ME/CFS, two are especially noteworthy and therefore, warrant additional attention: post-exertional malaise (PEM) (7) and serum acylcarnitine level (8). In this report, we present a review of the literature concerning these two features and describe the case of a patient for whom we were able to correctly diagnose ME/CFS based on accurate history-taking and clinical examination.