[Biochemical analysis of an uncommon monoclonal peak on urine protein electrophoresis: a case report].

Urine protein electrophoresis is often required for diagnosis and monitoring of urological or renal diseases and lymphoid hemopathies. We here report an uncommon urine protein electrophoresis result. The test was performed using agarose gel electrophoresis and capillary electrophoresis. It was a monoclonal peak of unknown significance migrating with gammaglobulins. Scientific literature and the tests performed demonstrated that it was myoglobin. In fact, myoglobin (17 kDa) is freely filtered by the glomerulus and normally reabsorbed by the tubules. If tubule capacity for reabsorption is exceeded, its presence results in overcharging proteinuria. Myoglobinuria helped diagnose rhabdomyolysis in our patient. Thus, the analysis of unknown peaks, can provide information on symptoms but also underlying pathologies, which may be of clinical interest.