The patient reported in the foregoing letter is of particular interest in view of the recent observations on patients with tnisomy 21 and cystic fibrosis. The multiple possibilities that could explain the clinical presentation have no doubt been considered by the authors. However, the description of "hypoplastic thrombocytopenia" and later pancytopenia in this patient, associated with pancreatic insufficiency, leads to the serious consideration of Shwachman's syndrome (pancreatic insufficiency and bone marrow dysfunction). The wide discrepancy between the sodium and chloride concentrations in the sweat reported in their letter indicates that evaporation of water may have occurred from the sweat sample, leading to an apparently higher sodium and chloride concentration.