Metabolic etiologies of cyclic or recurrent vomiting

Treatable metabolic diseases are infrequently considered in the differential diagnosis of a child with cyclic or recurrent vomiting. Helpful clues in a complete medical history can heighten a clinician's suspicion about a metabolic etiology, as can the presence of certain symptom complexes or biochemical features. A rational approach to investigation is discussed using routine laboratory tests as a first-line screen. More definitive testing is indicated when screening results are abnormal or when the patient's history is particularly suggestive. Until test results become available, patients in whom a metabolic etiology cannot be ruled out should be treated as if they have an inborn error, in parallel with other conventional therapies, to avoid complications that are often preventable.