G.P.317: Renal dysfunction in patients with Fukuyama congenital muscular dystrophy

Abstract

Fukuyama congenital muscular dystrophy (FCMD), characterized by intellectual deficits and epilepsy with cortical migration defects, is the most common congenital muscular dystrophy in Japan. Most patients die of congestive heart failure or respiratory dysfunction, as in Duchenne muscular dystrophy (DMD), in the second decade of life. Recent studies have found that renal dysfunction is a common complication of advanced DMD and is the third leading cause of death in these patients. Circulatory instability caused by cardiac dysfunction is thought to result in renal dysfunction, especially prerenal failure. We retrospectively evaluated renal function in 37 genetically diagnosed FCMD patients (1.3–32.9 years, mean age 13.7 ± 6.9 years) using Cystatin C. We examined possible relationships of Cystatin with the levels of blood natriuretic peptide and creatinine, as well as the cardiac echo results. Twenty-four patients were treated for cardiac dysfunction, but elevated Cystatin C was detected in only two. These two patients also showed proteinuria, glycosuria, hematuria and extremely high levels of β2-microglobulin on urine tests and were thus diagnosed as having kidney tubule cell damage. Since both patients were treated for intractable epilepsy with many types of antiepileptic drugs, including valproic acid (VPA), and had low serum carnitine levels, kidney tubule cell damage was thought to be an adverse effect of VPA. One patient improved in response to a reduced VPA dose, but the other developed Fanconi syndrome. Unlike DMD patients, none of our FCMD patients progressed to prerenal failure. Though FCMD patients also have cardiac dysfunction, careful fluid management is instituted early because dysphagia emerges in the early stage. In DMD patients, inadequate fluid management may also cause circulatory instability, which can progress to prerenal failure. On the other hand, kidney tubule cell damage should be noted in FCMD patients especially with VPA treatment for epilepsy.