On Oct. 13, 2013, 12-year-old Landon Jones was eating pizza and ice cream. Since a lung infection on Oct. 14, 2013, Landon's parents have to repeat instructions like a mantra for Landon to remind him to eat and drink. Landon's weight has dropped from 104 lbs. to 68 lbs., according to The Des Moines Register, and he can't play, participate in school or function like a normal child his age. He sometimes must be force fed.

Landon never feels hunger or thirst, despite having normal senses of smell and taste. He has undergone a spinal tap, brain scans, abdominal imaging, encephalograms, psychiatric evaluations, nutritional consultations and doctor's appointments in five cities, but doctors have not been able to diagnose the issue, according to LiveScience.

Dr. Marc Patterson, a pediatric neurologist at the Mayo Clinic in Minnesota with 33-years of experience, has been treating Landon. He told The Des Moines Register that he has never seen another case like Landon's and that Landon may be the only person in the world with this misfortune.

The problem could be due to a malfunctioning hypothalamus, a pea-size region at the base of the brain that controls vital functions like hunger, thirst, body temperature, blood pressure and sleep. The hypothalamus is allied with the pituitary gland, which regulates stress response. Hypothalamic breakdown can be caused by infection, malnutrition, genetic disorders, head injury or tumors, according to CBS News. "The challenge of understanding brain function out of the tool kit we have ... is still quite inadequate," Patterson told The Des Moines Register.

Possibly the bacteria that infected Landon's lung crossed the blood-brain barrier and damaged his hypothalamus with an infection of lesion, according to LiveScience. "It makes sense that the two go hand in hand, because hunger and thirst are both controlled by the hypothalamus," said Dr. Caroline Messer, an endocrinologist at Lenox Hill Hospital in New York City.

Another possibility is hormone resistance. If Landon has developed a resistance to the hormone ghrelin, which fuels hunger, or now has an overproduction of the hormone leptin, which causes feelings of fullness, it would explain his lack of hunger, Messer told LiveScience. The lack of thirst would not be accounted for in this theory.

Landon's family has now turned to the National Institutes of Health, according to CBS News. The program sees only 50 to 100 patients with rare, undiagnosed diseases at its Maryland campus each year. Landon's family hopes he will be invited.

A "faint lead" suggested by The Des Moines Register is the drug Depakote Landon took three years ago for absence seizures. His pediatrician asked the NIH to review the possibility.

"One would hope he'll outgrow this," Mehta told LiveScience. "But for now, [Landon's family] will have to keep a close eye on calorie intake."