We describe a 10 month old boy with alpha-mannosidosis who presented with recurrent bronchopneumonia and diarrhea. Facial coarsening, deafness, hepatosplenomegaly, umbilical hernia, pectus carinatum and widespread Mongolian spots were distinguishing features. He also had mild skeletal deformities grouped together as 'dysostosis multiplex', and vacuolated lymphocytes on peripheral blood smear. These findings coupled with an abnormal urinary oligosaccharide pattern led to the suspicion of a lysosomal storage disease in the patient which proved to be alpha-mannosidosis. An exceptionally low level of alpha-mannosidase activity was subsequently found in serum and cultured skin fibroblasts. The patient's brother, who had died at the age of 10 months, had similar features. To the best of our knowledge, this is the first case reported from Turkey.