First case report of Mammomonogamus (Syngamus) laryngeus human infection in Colombia Parasitic nematodes of the genus Mammomonogamus affect the respiratory tract of domestic mammals. The male and female of M. laryngeus remain in permanent copula so that the pair appears as a "Y'. To date, a few more than 100 cases of human infections by this parasite have been reported in the biomedical literature. This report describes the first infected patient in Colombia. He had a persistent and productive cough and after an episode of coughing a pair of worms were expelled in sputum with total clinical recovery. Since there is scant clinical information about this parasite, this report includes a description of the adult worms, a summary of the epidemiology and the clinical manifestations in humans. Photographs are presented to facilitate future identification by morphological characteristics.