Systemic lupus erythematosus presenting as hyponatremia-associated rhabdomyolysis: A case report

RATIONALE: Systemic lupus erythematosus (SLE) is an autoimmune disease that involves multiple organs and causes various clinical manifestations. Cases of rhabdomyolysis as the initial presentation of SLE are rare, and there are no reported cases of SLE presenting hyponatremia-associated rhabdomyolysis as the first manifestation. Herein, we report a case of SLE with lupus nephritis in a patient with acute hyponatremia-associated rhabdomyolysis. PATIENT CONCERNS: A 44-year-old woman was admitted with complaints of altered consciousness, myalgia, and red-brownish urine that first appeared three days prior. Peripheral blood tests revealed elevated creatine kinase (19,013 IU/L) and myoglobin (5099 U/L) levels and severe hyponatremia (111 mEq/L) with no azotemia. Urinalysis showed nephritic sediments. DIAGNOSIS: Whole-body bone scintigraphy showed increased uptake of radiotracer in the both upper and lower extremities. Serological evaluation revealed the presence of anti-nuclear (speckled pattern, 1:640), anti-double stranded DNA, and anti-Smith antibodies and absence of anti-Jo-1 antibody. A kidney biopsy demonstrated mesangial proliferative (class II) lupus nephritis. INTERVENTIONS: Fluid therapy, including intravenous administration of 3% NaCl, was initiated. After three consecutive days of intravenous methylprednisolone (1 g/d), oral prednisolone (1 mg/kg/d), mycophenolate mofetil, and hydroxychloroquine were administered. OUTCOMES: On day 28, the patient was discharged with marked resolution of SLE-associated symptoms and laboratory findings. Lupus reactivation was not present during the subsequent six-month follow-up. LESSONS: Hyponatremia-associated rhabdomyolysis can be the first manifestation of SLE. Moreover, prompt fluid therapy and timely administration of immunosuppressive agents in SLE patients presenting with hyponatremia and rhabdomyolysis can significantly help alleviate disease activity and improve clinical outcomes.