De Clerambault's Syndrome
De Clerambault’s syndrome is also known as erotomania which was first described by G.G. De Clerambault in 1885.
An individual with this syndrome has the delusion that someone is secretly attracted to him/her. In the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, erotomania is listed as one of the subtypes of delusional disorder. As the cases commonly involved women, it was dubbed as “Old Maid’s Insanity”. One of the most potent characteristics of this syndrome is denial as those with this condition cannot accept that the admired person is already married or not reciprocally interested.
For instance, one of de Clerambault’s patients stood outside the Buckingham palace for many hours with the unshakeable belief that the king was communicating with her by moving the curtains. Interestingly, erotomania is frequently a cause of stalking behavior.