- Idiopathic low molecular weight proteinuria associated with hypercalciuric nephrocalcinosis in Japanese children is due to mutations of the renal chloride channel (CLCN5). Lloyd, S.E., Pearce, S.H., Günther, W., Kawaguchi, H., Igarashi, T., Jentsch, T.J., Thakker, R.V. J. Clin. Invest. (1997)