A 17 year old female sustained a head injury last summer, then problems began to surface during the fall which led to her diagnosis of type 1 diabetes, but she has no family history of diabetes. The doctor was surprised at her diagnosis, considering the family history and her own good health history. Could a misdiagnosis occur between diabetes insipidus and diabetes mellitus? Could there be a connection between the head injury and the diagnosis?

I don’t think there was a misdiagnosis. At 17 years of age, diabetes mellitus is mostly due to insulin deficiency. She probably has either type 1A (autoimmune) or type 1B diabetes mellitus. Type !A is the most common and is usually caused by a process in which the immune system mistakenly attacks and destroys the beta cells. It’s an autoimmune process that can have with no symptoms (apparently good health) and occur suddenly at a very late stage just prior clinical onset. In 90% of the cases, there is no family history of diabetes.

Diabetes insipidus is characterized by hypotonic polyuria, but there is no sugar in the urine as is true for diabetes mellitus. It is due to the absence of vasopressin (hypothalamic, or central, diabetes insipidus) or lack of kidney response to vasopressin (nephrogenic diabetes insipidus). Trauma may be implicated in the etiology of central diabetes insipidus but not type 1 diabetes.

MS