In this article, neutron activation analysis was used to identify 22 microelements in the hair of children suffering from nephrotic syndrome with observed changes in the gastrointestinal tract. The results obtained from 62 children in the exacerbation phase of atrophic gastroduodenitis and 32 children in remission were analyzed. At the onset phase of the disease, a decrease in the levels of essential microelements such as copper, iron, and selenium was detected, along with an increase in "toxic" microelements such as arsenic and manganese, indicating disturbances in the form of polymicroelementosis.