[Trimethylaminuria: three different mutations in a single family]

Background: primary trimethylaminuria or fish odor syndrome is a genetic metabolopathy characterized by the accumulation of trimethylamine, a very volatile compound in body secretions. Case report: we present the case of a healthy 8-month-old patient who, after the introduction of fish in the diet, starts a bad body odor that does not disappear with bathing. The mother visits the pediatrician repeatedly but no disorder is identified. The diagnosis is delayed until the patient is three years old. Due to maternal insistence, the patient is referred to our hospital unit, where genetic diagnostic tests are performed, enabling the paternal diagnosis that had gone unnoticed for 35 years and detecting three different mutations in the family. Discussion: primary trimethylaminuria is a genetic disease with specific symptomatology of bad body odor that can go unnoticed for many years. An adequate clinical suspicion and the request of adequate complementary tests allow its diagnosis and facilitate its clinical management.