Nesidioblastosis in a simmental calf.

A 2-day-old Simmental calf with arthrogryposis and astasia was subjected to necropsy examination. The calf was normoglycaemic and normoinsulinaemic. Microscopically, pancreatic tissue was hyperplastic with an irregular lobular arrangement of pancreatic islets. Newly-formed islet cells budded from intralobular or intercalated ducts (so-called ductulo-insular complexes) and there were prominent blood vessels with telangiectatic features surrounded by rows of cuboidal-columnar islet cells. The newly-formed islets expressed insulin antigen immunohistochemically. The lesion was diagnosed as nesidioblastosis, an uncommon abnormality previously associated with the double muscling trait in cattle.