Four families with hyperproinsulinemia found in Japan were described.
The details of the first case, who was investigated by Kanazawa et al.
, were reported and the similarity of the first case to the following
cases was shown. Arginine 65 of the proinsulin molecule might be a hot
spot of the insulin gene. A possible abnormality of insulin release i
n affected individuals was disclosed by investigation of the family me
mbers of the first case.