We present the case of a male patient suffering from a primary amyloidosis and a nephrotic syndrome who came to dietotherapy clinic. In the first visit we made a nutritional record including an anthropometric evaluation, body composition, biochemistry, and food intake. The patient had an excess of body water, proteinuria, low plasma protein, albumin, prealbumin and HDL cholesterol levels, and high concentrations of total cholesterol, LDL and triglycerides. The consumption of protein and sodium was higher than the recommendation. An individualized diet was made. Six months later, his weight and the excess of body water decreased, but the fat free mass remained unchanged. The levels of albumin and prealbumin increased, the proteinuria decreased. Total cholesterol, LDL and triglycerides decreased until normal levels. Dietetary treatment in nephrotic syndrome is effective to decrease proteinuria, improve cholesterol and triglycerides levels, and to prevent malnutrition.