ZnT8 antibodies in patients with cystic fibrosis: an expression of secondary beta-cell damage?

Cystic Fibrosis-Related Diabetes (CFRD) is caused by a severe insulin deficiency with associated different degrees of insulin resistance. Data concerning the potential impact of autoimmunity are conflicting. Ninety subjects with cystic fibrosis (CF) were tested for glucose tolerance and autoantibodies against insulin (IAA), glutamic acid decarboxylase (GADA), protein tyrosine phosphatase (IA2) and zinc transporter 8 (Znt8A). Eighty-three subjects showed a normal glucose tolerance (92.2%), 6 subjects (6.6%) impaired glucose tolerance and 1 subject (1.1%) newly diagnosed CFRD. Four subjects were found positive for both IAA and GADA (4.4%), one subject (1.1%) for both IA2 and GADA, and one subject (1.1%) for isolated GADA. Three subjects (3.3%) showed isolated ZnT8A positivity. ZnT8A positivity in CF patients is uncommon and not associated with other autoantibodies. ZnT8A may not represent a specific indicator of a primary autoimmune beta-cell destruction, but possibly the expression of a secondary damage of the pancreatic islets with autoantigen release.