The story is both tragic and surreal. To see your teenage daughter balloon to six hundredweight, a bloated blob of flesh so heavy she could not move from her bed, is possibly a parent's worst nightmare. The stretcher used to remove Christina's corpse broke and it took four firemen and two deputy coroners to lift her. She was unwashed and covered in bed sores and fungal growths. She had been unable even to heave herself off the sofa to get to the bathroom.
How is it possible for a person - a child - to consume so many calories? Marlene Corrigan's lawyers believe they have the answer. They are claiming that her daughter was suffering from Prader-Willi syndrome, a rare condition whose main symptoms are an uncontrollable appetite and a tendency to temper tantrums. Sufferers also commonly have weak muscles, under-developed genitals, and sometimes facial characteristics including almond eyes and a fish- shaped mouth, and a low IQ.
Rosemary Johnson, spokeswoman for the Prader-Willi Syndrome Association in the UK, said: "My first thought when I read about this case was that she could be a Prader-Willi. As well as her obesity she apparently could be quite bloody minded - that also fits in. If she was obstinate and narrow- minded, she could have made life hell for her mother."
The most difficult aspect of the syndrome, for parents and sufferers alike, is the obsession with eating. Sufferers have been known to eat 4,000 calories in two hours (a day and a half's meals for an average person). They will steal food from the kitchen and squirrel it away for snacks later. They will scavenge in rubbish bins and have been known to eat wallpaper, bedding, even polish. One died after eating large quantities of jam and salt.
What makes people eat without stopping? Christina Corrigan was already so heavy at the age of nine, when she last saw a doctor, that she had difficulty walking the short distance from her home in Martinez, California, to school. She weighed 17 stone and her doctor said she should eat less and exercise more.
Four years later her weight had almost tripled. She spent her last months in front of the television, unable to leave the family room. She could find no clothes to fit and wore either a kaftan crocheted by her mother or lay naked under a blanket.
What Prader-Willi sufferers lack is the sense of fullness that the rest of us get after eating a good meal. They only feel full when there is, literally, no more room. For most people the sense of fullness comes long before, through a complex mechanism of chemical messengers travelling between gut and brain. Investigation of the breakdown of this mechanism in Prader-Willi patients could one day yield clues to the western world's great obsession: the control of eating.
Prader-Willi syndrome was first spotted in the UK 35 years ago by Dr Bernard Laurance (my father, as it happens) but is named after the two Swiss doctors who had earlier described it in a German medical journal. It is caused by a defect on chromosome 15 which is now detectable in almost all cases by a blood test. The defect is believed to occur at or near conception, but because those affected do not develop sexually, they cannot pass it on.
Between 3,000 and 5,000 people are thought to have the syndrome in the UK and there is no cure. Although it is now better understood, it remains a grim diagnosis. Parents must rely on tough management which often means locking kitchen cupboards and the fridge and exerting tight control over diet. Early diagnosis so that the strict dietary regime can be imposed from the start, before weight begins to rise, improves the long-term prospects.
Christina Corrigan was an apparently normal 7lbs 11oz baby but by the time she was three her weight had soared off the charts to 60lbs and at five it was up to eight stone. Hospital tests for diabetes and thyroid function failed to disclose any problem and from the age of eight she apparently gave up on dieting, refusing to follow her mother's strictures or to join her on cabbage soup diets.
From the age of 11 she refused to go to school because of taunts about her weight. Eventually she refused to leave the house. Mrs Corrigan said: "How could I get her out of the house? I couldn't pick her up and carry her. Everything was because of her weight."
The desperate circumstances of Christina Corrigan's short life and early death demonstrate how the loss of appetite control can kill. In Britain in the mid-1980s, a 25- year-old man with Prader-Willi syndrome died weighing 46 stone. The Sun reported that a JCB digger was required at his funeral to lift the coffin.
Mrs Johnson, whose 17-year-old son, Matthew, is a sufferer, said: "At that time, we all thought that is how our children would end up. Now we know it isn't so and it is important not to be too depressing for parents whose children are newly diagnosed. There is reason to assume they may not stay delicately thin but there is no reason why they should become grossly bloated and obese, with proper management."
Matthew, who was diagnosed at six months, is a normal weight for his height of 5ft but this has only been achieved as a result of the iron discipline imposed by his mother. "He has no choices. What he gets is what he eats," she says.
He is now away at college but the canteen is under strict instructions to take his order the day before and serve him fixed portions. He is not free to pick and choose as the other students are.
"It is much more difficult when they grow up and leave home. Living independently is not a safe option for Prader- Willi sufferers because of the emotional and control issues."
A simple blood test could have established whether Christina Corrigan was a Prader-Willi sufferer but for the last four years of her life she had no medical attention. Mrs Johnson said: "There may have been other causes for her condition. But I cannot understand why her mother didn't involve someone else. Where were the teachers and social workers? Why didn't someone step in and help?"
The Prader-Willi Syndrome Association (UK) can be contacted at 2, Wheatsheaf Close, Horsell, Woking, Surrey GU21 4BP. Tel: 01483 724784