A 58‐year‐old woman presented to our emergency room with low back pain and malaise to the point of being unable to perform activities of daily living for 1 week. She has a medical history significant for nephrolithiasis and carnitine palmitoyltransferase II (CPT II) deficiency, causing one documented episode of rhabdomyolysis 16 years prior to presentation. She described experiencing progressive, nonradiating back, hip, and shoulder pain along with dysuria, subjective fevers, and malodorous dark brown urine for 1 week. On arrival, she was febrile at 38.6°C and tachycardic to 95 bpm, with diffuse tenderness bilaterally in her upper and lower extremities. She also displayed significant costovertebral angle tenderness and moderate pain on palpation along the posterior superior iliac spine. Laboratory findings were significant for a urinalysis positive for leukocyte esterase, nitrites, large amounts of blood with 10 RBCs/HPF. Creatine phosphokinase peaked at 162,177 IU/L and her serum creatinine peaked at 299.68 μmol/L. Urine Cultures were positive for E. coli. CT scan of the abdomen without contrast was performed to rule out nephrolithiasis and showed chronically scarred and atrophic bilateral supernumerary kidneys with nonobstructive renal calculi in the native and supernumerary kidneys. In addition, fat stranding was noted adjacent to the right native and supernumerary kidney, indicative of pyelonephritis. Rhabdomyolysis with acute kidney injury in the setting of CPT II deficiency was successfully treated with the standard protocol of high‐rate IV fluid resuscitation and a 14‐day course of antibiotics for the pyelonephritis.
CPT II is an enzyme found along the inner membrane of the mitochondrial matrix and is essential for long chain fatty acid oxidation. Adult onset CPT II deficiency is an autosomal recessive disorder that affects skeletal muscle. Therefore, patients commonly present with intermittent myalgias and myoglobinuria secondary to stress. Bilateral supernumerary kidneys, an extraordinarily rare anatomic finding of which only three cases have been reported in the literature, arise due to ureteric buds interacting with additional metanephric blastemal masses during nephrogenesis. It is postulated abnormal ureter formation predisposed this individual to an increased risk of nephrolithiasis and pyelonephritis that subsequently led to severe rhabdomyolysis secondary to CPT II deficiency.
Because of the limited nature of supernumerary kidneys in the population, there are no clear recommendations regarding long‐term surveillance; however, in the setting of CPT II deficiency, the role of prophylactic supernumerary nephrectomy to prevent major renal sequelae of recurrent rhabdomyolysis should be considered.