Appears to be genetic, passed down from the fraternal side and is possibly related to being introverted.
PMS is not fatal, however spouses/partners may experience strong feelings of malcontent towards those afflicted with the syndrome.
Symptoms (this is not a complete list, symptoms may vary):
A reluctance to participant in family occasions, especially around holidays or birthdays, is common.
May grunt and/or have gruff responses to routine questions such as, "What would you like for dinner?"
May indulge in excessive reading, TV watching, or puttering in the garage.
May experience a temporary paralysis of their sense of humor.
May have selective hearing.
May appear to have a sleep disorder.
May leave the house without telling anyone where they are going.
May refuse to talk on phone to other family members.
May appear perfectly normal, even jovial, when others outside the family are around. Reverts to silence when outsiders have departed.
There is no known cure at this time.
Often symptoms disappear on their own when holidays are over.