Allergy to Cow’s Milk Proteins and Other Allergens—An Unrecognized Co-Factor of Idiopathic Nephrotic Syndrome in Children or a Factor Interfering with the Treatment of This Disease? A Case Report

Idiopathic nephrotic syndrome (INS) is one of the chronic kidney diseases that occurs in childhood. Starting from a few case reports in the 1950s–1970s and up to the present, the relationship between idiopathic nephrotic syndrome (INS) and the occurrence of atopic disorders in these patients has been discussed in many medical publications. These publications show that in certain patients, mainly children and adolescents, but also in adults with INS, various clinical symptoms and laboratory indicators of an atopic allergic process may be present. This process has been shown to involve Th2 lymphocytes, to have an excessive production of interleukins (IL-4, IL-5, IL-13), and to have an increased serum level of immunoglobulin E (IgE). This leads to the development of a systemic allergic inflammatory process, of which the kidneys can also become the effector organ. The coexistence of an allergic process which may adversely affect the course of nephrotic syndrome may be confirmed by the increased serum IgE level and the hypersensitivity reaction of the patient’s body to various environmental allergens (through the presence of allergen-specific IgE /asIgE/ antibodies to food, pollen, mould, dust, or other allergens in the blood serum). High concentrations of IL-13 and other plasma mediators of this inflammation (e.g., histamine, bradykinin) structurally and functionally damage the renal filtration barrier, and in particular, the function of podocytes in the glomeruli. Podocyte dysfunction disturbs the physiological process of plasma filtration in the glomeruli, leading to excessive protein loss in the urine. These disorders initiate the development of idiopathic nephrotic syndrome in these patients. This publication presents the coexistence of an allergic process caused by allergy to cow’s milk proteins and hypersensitivity to other allergens in a child with idiopathic nephrotic syndrome. This publication also assesses whether treatment of the allergic process coexisting with INS with an elimination diet (milk-free, hypoallergenic) and anti-allergic drugs affected the course and treatment of INS in this child.