Two siblings poisoned with diphenhydramine: a case of factitious disorder by proxy.

We report a case of factitious disorder by proxy (FDBP), formerly known as Munchausen syndrome by proxy, in which 2 siblings were poisoned with diphenhydramine. Although diphenhydramine is a readily available medication, no report of its use as the sole agent in an FDBP case was found in a literature search. Although sibling involvement in FDBP is well documented, this is the first case report of 2 siblings hospitalized simultaneously because of intentional poisoning with the same substance. Finally, the use of physostigmine to definitively diagnose anticholinergic poisoning in a case of FDBP has not previously been described.