Mine-itis is a Grouch disease which causes infected individuals to exhibit high levels of egoism and selfishness. The disease gives individuals a sense of entitlement to other's belongings; in some cases, individuals exhibit paranoid hoarding of various possessions.
The symptoms of Mine-itis come in stages: first, the infected individual will feel itchy. Soon after, they will start to hop like a kangaroo, followed by a bout of uncontrollable spinning. During the final stage the infected individual will display intense greed and selfishness. Those infected with Mine-itis will often mindlessly wander chanting "mine, mine" while clinging to others' belongings and displaying a uncontrollable hunger for possessing more and more.
Mine-itis is cured by having a Grouch show civility and kindness by sharing something of theirs with an infected individual.
In 2008 a Mine-itis epidemic broke out on Sesame Street in New York, NY. Fourteen individuals were known to contract the disease on the street -- Bert, Grover, Cookie Monster, Big Bird, Mr. Snuffleupagus, Alan, Bob, a chicken, Luis, Maria, Gabi, Gina, Gordon and Brian Williams. The events of the epidemic were seen in Sesame Street episode 4181 when Brian Williams of Sesame Street Nightly News reported on the outbreak as it unfolded. Two individuals, Leela and Elmo, were unaffected by the outbreak despite prolonged contact with infected individuals. The residents of Sesame Street were ultimately cured by the reluctant kindness of none other than Sesame Street's local Grouch, Oscar.
Mine-itis comes from the possessive pronoun Mine plus the suffix -itis (which refers to inflammation, but in colloquial speech is often used to simply mean illness).