CST3 and kidney disorder: It was possible that he had subclinical renal insufficiency due to his underlying MMA even though his glomerular filtration rate (GFR) was not reduced without significant elevations of creatinine and cystatin C. It was suggested that a nephrotoxic immunosuppressant, tacrolimus is likely to have triggered worsening kidney injury in the face of preexisting subclinical kidney disease from MMA.