When they are moved to a nurturing environment, they grow rapidly and their abnormal behavior improves.
Psychosocial dwarfism has been well-documented since the 1960s, but it is so uncommon that even leading child-abuse experts rarely see a case.
"I've seen only a handful of cases in over 15 years," said Cindy Christian, a pediatrician who directs the Center for Child Protection and Health at Children's Hospital of Philadelphia.
Now, as experts read media reports about the Jackson family, they cannot help wondering whether this obscure disorder could be a piece of the puzzle.
The four Jackson boys, ages 9 to 19, all extremely undersized for their ages, were removed Oct. 10 from the Collingswood home of their adoptive parents, Raymond and Vanessa Jackson. The Camden County couple, accused of starving the boys, have been charged with child endangerment. But friends, a pastor and relatives - including the couple's four biological children - insist that the Camden County couple are loving, devoted parents who took in the boys despite their histories of abuse, neglect and behavioral problems.
The couple have said that Bruce, 19, who came to them as a sexually abused 7-year-old foster child, gorged and vomited, stole and hoarded food, regurgitated and reswallowed food, and ate out of garbage bins. He was eating out of a garbage can when a neighbor called police last month. The neighbor guessed that the high-voiced teenager, 4 feet tall and 45 pounds, was 9 years old.
Now under medical supervision, all four boys have gained significant amounts of weight, but Bruce's progress has been the most dramatic. His weight has jumped to 66 pounds, and he has grown at least an inch in height, state officials say.
Kevin Ryan, New Jersey's independent child advocate, said Friday that the evidence pointed to starvation as the reason the boys' growth was stunted. However, he said, he would not dismiss other possibilities, including psychosocial dwarfism.
"I'm not ruling it out," Ryan said.
Ryan said that in an effort to understand better what has happened, his office has subpoenaed the boys' medical records and is continuing discussions with clinicians treating them.
Many chronic diseases and congenital abnormalities can inhibit growth and cause short stature, including dwarfism, hypothyroidism, pituitary tumors, anorexia, cystic fibrosis, diabetes and Turner's syndrome.
But if diagnostic tests and examinations rule out these causes, a doctor has to consider social and psychological stresses, said Angelo Giardino, a St. Christopher's Hospital pediatrician who, like other doctors interviewed, has no direct knowledge of the Jackson case.
Giardino drew an analogy between the chronic mental and emotional stresses that can lead to a heart attack, and the chronic emotional deprivation that can suppress growth hormones.
"Psychological stress can have physiological effects," he said.
New Jersey officials have said they plan to gather full psychological profiles on all four brothers in the coming weeks.
Robert Blizzard, an emeritus professor of pediatrics at the University of Virginia, was among the first to document psychosocial dwarfism, in the 1960s and 1970s. Unfortunately, he said, "social workers and judges may not understand this disorder."
At the core of this complex illness is a disturbed relationship between a child and the parent or caretaker. There may be outright abuse, rejection or abandonment of the child. Or, a caring parent may be unable to bond adequately with the child because of substance abuse, depression, or his or her own emotional problems.
In the 1960s, new technology enabled researchers to prove, by measuring hormone levels in the blood, that the mind could influence growth through hormone imbalances. They found that severe, sustained emotional deprivation could suppress the primary growth hormone, disrupt thyroid function, and make target cells less sensitive to growth hormones.
Still, diagnosis of psychosocial dwarfism is tricky, because some of these children also are malnourished, a condition that by itself inhibits growth.
How can observers tell what's really going on?
Diagnosis is confirmed by moving the child to a safe, nurturing environment and watching for sudden "catch-up" growth, said Andrew P. Sirotnak, a pediatrician and child-abuse expert at the University of Colorado Health Sciences Center in Denver.
In a medical textbook, Blizzard cites numerous cases, including these:
A girl, age 15, was referred to psychiatrists because she had not begun puberty, was the size of a 10-year-old, habitually drank from a toilet bowl, ate dog food, and was academically delayed. Her home was "emotionally unstable," and she hated her father so much that she would not talk to male doctors. One month after being hospitalized, she grew an inch and began sexual maturation.
A malnourished 9-year-old boy - born of the sexual liaison between a mildly retarded teenager and her brother - was taken to doctors after three difficult years with foster parents whom authorities considered to be religious, conscientious, caring people. The boy was the size of a 5-year-old. The foster parents said he ate dog food, garbage and feces, had violent tantrums, and banged his head against walls. During a month of hospitalization, he became more outgoing, ate ravenously, and gained 18 pounds. He said his foster parents had punished his behavior by withholding food and drink and locking him in his bedroom at night to keep him from eating.
In the Jacksons' case, the parents said they had put an alarm on the kitchen door to prevent Bruce from sneaking in, then gorging and vomiting. Vanessa Jackson told authorities she had not taken the boys to a doctor for four or five years.
Experts say that children who suffer from psychosocial dwarfism tend to be emotionally and psychologically unstable when they grow up, particularly if the disorder is diagnosed late in childhood.
That, experts agree, is why parents should seek help - and why they cannot understand how the Jacksons got into such a deep crisis.
"Functional families ask for help," said Giardino of St. Christopher's Hospital. "When did the pattern not make sense in terms of the boys' growth? . . . When was someone going to pull the rip cord on the parachute?"
Contact staff writer Marie McCullough at 215-854-2720 or firstname.lastname@example.org.
Staff writers John Shiffman and Mitch Lipka contributed to this article.