A four-month-old boy was admitted with vomiting, diarrhoea and severe weight and body weight delay. He presented hypotonia, bilateral convergent strabismus and inverted nipples. Healthy, non-consanguineous parents, normal pregnancy and delivery. Since the age of one month she has had poor intake, growth failure and vomiting, with normal abdominal and transfontanelar ultrasound, chest X-ray, blood tests and urine culture.

On admission, rotavirus was detected in stool. After resolution of the acute process, nutritional support was started with artificial protein hydrolysate formula; later, the patient was switched to elemental formula as he continued to show poor weight gain. The study performed detected hypertransaminemia, hypoalbuminemia, decreased transferrin and ceruloplasmin, with normal hepatotropic virus serology and echocardiography. Given the suspicion of a possible inborn error of metabolism (IEM), a metabolic study was requested, while the patient required admission to the Intensive Care Unit due to the onset of symptoms compatible with sepsis (fever, hypoglycaemia, poor general condition and poor colouring). A cranial MRI scan was performed, which showed cerebellar hypoplasia. The result of the metabolic study confirms a congenital protein glycosylation defect (CGD) type Ia.