Autoimmune polyglandular syndrome (APS) is a combination of different autoimmune diseases. The close relationship between immune-mediated disorders makes it mandatory to perform serological screening periodically in order to avoid delayed diagnosis of additional autoimmune diseases. We studied a patient with type 1 diabetes (T1D) who later developed an autoimmune thyroid disease (ATD) and was referred to our hospital with a serious condition of his clinical status. The patient was suffering from an advance stage of celiac disease (CD), the delay in its diagnosis and in the establishment of a gluten-free dietled the patient to a severe proteincalorie malnutrition. Later, the patient developed an autoimmune hepatitis (AIH). We consider that clinical deterioration in patients with APS should alert physicians about the possible presence of other immune-mediated diseases. Periodic screening for autoantibodies would help to prevent delayed diagnosis and would improve patient's quality of life.