Discussion

This case illustrates several important diagnostic challenges in the outpatient evaluation of progressive muscle weakness in a patient receiving statin therapy. The patient’s initial symptoms were nonspecific and could easily have been attributed to hypothyroidism, chronic fatigue, viral illness, diabetic complications, or musculoskeletal disorders. However, the presence of progressive functional decline, difficulty rising from bed, impaired ambulation, diffuse myalgia, and proximal muscle weakness warranted the measurement of serum creatine kinase (CK), leading to the early recognition of severe muscle injury [1,2,6,7].

The degree of CK elevation was markedly abnormal and far exceeded the range expected for uncomplicated statin-associated myalgia. In the setting of ongoing rosuvastatin therapy, this raised concern for severe statin-associated myopathy. The CK level subsequently increased from 8,586 U/L to 9,239 U/L by day 22 and remained markedly elevated at 3,550 U/L on day 54 despite statin withdrawal. Persistent hyperCKemia after statin discontinuation raises concern for anti-HMGCR antibody-associated IMNM, although a progressive decline in CK may also occur during recovery from severe toxic statin myopathy [3-5]. In this patient, the persistent elevation increased concern for immune-mediated disease and justified specialist evaluation, but the downward CK trend alone could not establish that diagnosis. Results of anti-HMGCR antibody testing, electromyography, muscle magnetic resonance imaging, and muscle biopsy were not available in the records accessible to the author, and it was unknown whether these investigations were subsequently performed within the public hospital system. Accordingly, this case is most appropriately described as severe rosuvastatin-associated myopathy with concern for an underlying immune-mediated inflammatory myopathy rather than confirmed IMNM [3-5].

Another important teaching point is the interpretation of aminotransferase elevation. Although AST and ALT were substantially elevated, bilirubin, alkaline phosphatase, gamma-glutamyl transferase (GGT), coagulation studies, and renal function remained preserved. In the context of severe hyperCKemia and progressive muscle weakness, the transaminitis was most likely attributable, at least in part, to skeletal muscle injury rather than primary hepatic disease. Recognizing this biochemical pattern is important because misattributing elevated aminotransferases solely to liver pathology may delay the diagnosis of severe statin-associated muscle injury [1,2,6,7].

This case also demonstrates why inflammatory markers should be interpreted within the broader clinical context. Although the initial elevation in CRP and ESR supported an inflammatory process, the subsequent marked increase coincided with a culture-confirmed Escherichia coli urinary tract infection. Therefore, the later inflammatory marker elevation cannot be confidently attributed to ongoing myositis activity alone.

Limitations of this case include the availability of only two direct outpatient evaluations and the absence of access to hospitalization and subsequent specialist consultation records. Although laboratory results through day 54 remained accessible because tests ordered by other treating physicians were performed by the laboratory associated with the author’s clinic, the patient’s subsequent treatment, recovery of muscle strength, final specialist diagnosis, and long-term clinical outcome could not be verified. Autoimmune testing was recommended at the second outpatient visit, but it could not be confirmed whether the requested tests were completed. It was also unknown whether anti-HMGCR antibody testing, electromyography, muscle magnetic resonance imaging, or muscle biopsy was subsequently performed. These limitations precluded definitive etiologic classification. Long-term clinical and laboratory follow-up is important to document recovery and exclude persistent immune-mediated disease.

Despite these limitations, this case reinforces the importance of maintaining a high index of suspicion for severe statin-associated myopathy in patients presenting with progressive proximal muscle weakness while receiving statin therapy. Early CK measurement, the prompt discontinuation of the offending medication, and appropriate specialist referral are essential to reduce morbidity and facilitate the timely diagnosis of potentially life-threatening muscle disease [1-7].