Only Child Syndrome (OCS) - a condition affecting strictly sibling-less children which is primarily characterized by an extreme self-absorbance, the inability to acknowledge the needs or wants of others, and a general disregard for all matters not concerning oneself.
While symptoms may appear to be merely annoying nuisances to observers, if left untreated, the persistent and pervasive effects of OCS symptoms can severely interfere with one's ability to mature into a functional member of society.
Those suffering with OCS often exhibit signs from an early age. They insist on vocabulary such as "my" or "mine" in conversation, show an extreme sense of possession, and demonstrate a general ignorance of social standards and expectations.
Person A: "Is anybody going to eat these last few pickles in this jar?"
OCS sufferer: "Those are mine; my mom bought them for me. Don't touch them, I might want them later."
Person A: "Hey, how was your weekend?"
OCS Sufferer: "Hey, my weekend was good. I went to my masseuse, I got my nails done, I bought a puppy who just loves me! But my boyfriend and I got in a fight. He just doesn't get me! I don't ask for much, I just want him to pay a little attention to me sometimes! Ugh, I just hate him. It's always all about him! Why can't he realize what I want is important sometimes too?!"
Person A: "Oh, rats, that sucks. What'd he do?"
OCS Sufferer: "He didn't call me on Saturday."
Person A: "What? Really, that's all? Well, my weekend was good too. Okay, bye!"