hello shalina Primary causes of nephrotic syndrome are usually described by the histology, i.e. minimal change disease (MCD) like minimal change nephropathy which is the most common cause of nephrotic syndrome in children it is common in preschool children. the nephrotic syndrome is mainly due to the loss of proteins from the kidney causing fluid to acumuate in the interstitial space. Call your health care provider if symptoms which may indicate nephrotic syndrome occur. i would advise you to consult a pediatrician and get a regular follow up done with regular appropriate blood investigations Call your health care provider if nephrotic syndrome persists or if new symptoms develop, including severe headache, fever, sores on the skin, cough, discomfort with urination, or decreased urine output. Go to the emergency room or call the local emergency number i hope i have answered your question, take care and wishing your son a speedy recovery