Screening for inborn errors of metabolism among newborns with metabolic disturbance and/or neurological manifestations without determined cause.

CONTEXT: Inborn Errors of Metabolism are hereditary affections resulting from incompetence in enzymatic reactions of intermediary metabolism. At present, several hundred hereditary metabolic disturbances are known, many of which correspond to severe life-threatening disorders.
OBJECTIVE: The early detection of carriers has motivated the screening for these disturbances among newborns at the Neonatal Unit of Hospital São Paulo, in an attempt to initiate support treatment, when available, before clinical manifestations become evident.
DESIGN: Prospective study of risk patients.
SETTING: Laboratory for Inborn Errors of Metabolism at the Center for Medical Genetics of the Departments of Pediatrics and Morphology of Universidade Federal de São Paulo/Escola Paulista de Medicina. Newborn care unit at a tertiary care hospital. PARTICIPANTS: 101 children admitted into the Neonatal Unit were included in this study by presenting hypoglycemia, metabolic acidosis, jaundice, difficulty in gaining weight, diarrhea, vomiting, hepato- and/or splenomegaly, cataracts, apnea, convulsions, hypo- or hypertonia. DIAGNOSTIC TESTS: Tests routinely utilized, performed for qualitative research of abnormal substances excreted in the urine in situations of metabolic disorder.
RESULTS: Children were included in the study mainly because of presenting hypoglycemia, jaundice and metabolic acidosis. Sixty-four newborns presented at least one positive test result. Most of the positivity was due to transitory metabolic alterations of the newborn, such as the case of Transitory Neonatal Tyrosinemia, presented by 29 patients. Nine infants were referred to the Center for Medical Genetics of Universidade Federal de São Paulo for continuation of the diagnostic investigation. For three of them, the tests applied permitted us to formulate a diagnostic hypothesis of mucopolysaccharidosis, tyrosinemia type I and non-ketotic hyperglycinemia, respectively.
CONCLUSIONS: The high positivity observed in the tests reflects the newborn's own metabolic immaturity. The selection of 9% of the studied cases for outpatient follow-up confirms that Inborn Errors of Metabolism must be suspected whenever a patient presents metabolic disturbances or neurological manifestations without a determined cause. They should be researched in parallel with the other diagnostic possibilities and not just taken to be exceptional diagnoses.