Not every elevating enzyme tells the same story: unpacking creatine kinase and anti-Jo-1 positivity beyond inflammatory myositis

Abstract

Gitelman syndrome (GS) is an autosomal recessive familial disorder characterized by hypokalemia and metabolic alkalosis. Rhabdomyolysis due to hypokalemia is extremely rare. The presentation of GS leading to rhabdomyolysis is extremely rare as well. This case report describes a situation in which GS mimicked inflammatory myositis. A 30-year-old woman presented to the rheumatology outpatient clinic with an inability to walk and severe muscle weakness. Her creatine kinase level was elevated at 9900 U/L and her potassium level was low at 2.6 mmol/L. A myositis panel was ordered on suspicion of inflammatory myositis, and the results showed a positive anti-Jo-1. A muscle biopsy, performed with a presumptive diagnosis of inflammatory myositis, yielded pathology results inconsistent with myositis. Despite persistent low potassium levels during follow-up, potassium replacement was administered. The patient’s clinical condition improved significantly with potassium replacement, leading to a reduction in muscle weakness.