PDD is sometimes called Autistic Spectrum Disorder (ASD); autism accounts for one-third of the cases, and most people with PDD have at least some autistic traits, such as difficulty with social and emotional interaction, repetitive behavior, and language dysfunction.

The news is that PDD is on the rise. In California, according to the California Department of Developmental Services, autism is up 273 percent over the last 11 years. PDD types including the category "Not Otherwise Specified" (PDD-NOS) that is the particular focus of this book have risen by nearly 2000 percent-astronomical even given the increased awareness of the disorder that probably accounts for some of the rise.

Profound personal experience often makes for the most compelling literature on a subject. At age two Waltz's son Ian communicated "with grunts and shrieks, and only occasionally sounds that resembled words...He was clumsy, constantly banging into furniture and falling, often with no sign of pain," wrote Waltz, adding the poignant words so many PDD parents have voiced: "We loved our little boy, but we knew something was not quite right."

Pervasive Developmental Disorders, however, is not a personal narrative. It is an exhaustively researched and referenced handbook for families and individuals coping with PDD. It walks us through the process of diagnosis; negotiation with health care and school systems that may not be well educated about PDD; early intervention and the various therapies; and dealing with finance and insurance. There's a "crash course in basic neurology" geared to non-technical readers, and advice born of personal experience, like her "Semi-sneaky tips" on getting around voice-mail barriers, staying calm, and using humor to get through the bureaucracy.

An appendix lists books and web resources for both adults and children with PDD, along with resources on general disability, health care and insurance, parenting, special education, and the many kinds of therapy.

"I wanted to write the book I needed when Ian was two years old," said Waltz. As such, said editor Linda Lamb, Pervasive Developmental Disorders is in the O'Reilly tradition of "people who have gone through hell trying to figure out what's going on and have then written a book about it."

Waltz is a technical editor with a degree in journalism, a background in investigative writing and research, and a lifelong interest in science and health. She is finishing a book on bi-polar disorder and researching one on obsessive compulsive disorder. She is the mother of Ian, now 8, and Carmen, 17.

New research on autism and PDD is focusing on finding biological markers for the disorders. Genetics plays a role in susceptibility, but other factors may be involved. For instance, researchers have recently linked such PDD-related behaviors as obsessive compulsive disorder and Tourette's syndrome with ordinary strep infection. "It's a reaction to strep antibodies," said Waltz, and it points to another PDD characteristic: a high frequency of autoimmune disorders, which in turn appear to be on the increase.

Symptoms of PDD-NOS are so varied that getting a correct diagnosis is a big hurdle. Furthermore, interventions that work for one child may actually hinder another's progress, pointing to the probability that PDD has a variety of genetic and environmental origins.

It's important to find the right doctor and to get a multidisciplinary evaluation, according to Waltz. Pediatricians are not equipped to recognize PDD. "It's not up their alley," said Waltz. "They're busy treating strep throat." Referrals must be made carefully. "Neurologists in particular are often not interested in or aware of PDD." Case studies abound in which patients suffered through a series of diagnostic attempts ranging through "cerebral palsy," "psychotic disorder," "borderline intellectual functioning," developmental delay," and the all-purpose "give him time, he'll grow out of it."

Waltz recommends finding knowledgeable local resources with the help of the Autism Society of America or the Autism Research Institute.

Although each person with PDD is unique, and differences from the norm can be subtle, there are some common threads. "Communication difficulties are often the first things parents notice," said Waltz. There may be physical problems such as clumsiness and unusual actions. Many PDD children are inordinately sensitive to stimuli such as sounds, smells, or the feel of stiff new clothing.

Children with PDD often find social interactions so confusing that they cope either by withdrawing or by being aggressive. But most are capable of warmth and affection.

"People have the idea that autistic kids don't have a relationship with anyone," said Waltz. However, all but the most severely autistic children are capable of relationships--especially with their parents. Parents instinctively or through diligent research tend to figure out what throws their children off track. Carefully designed behavior modification interventions and medications have been effective in widening the social and emotional world of those with PDD.

Waltz hopes for continuing research into behavior modification techniques such as applied behavior analysis, which may actually work to retrain brain circuitry, and into more precise medications and dosages for children with PDD.

What parent has not wondered if a child's problems are the result of bad parenting? The older literature laid heavy blame for autism on parents, but here there is reassurance and evidence that these disorders are not caused by poor parenting, abuse, or economic deprivation.

Meanwhile, some question whether the term "disorder" is altogether appropriate, given the unusual talents of many people with PDD. Waltz's father, for instance, was a successful engineer even though he was eventually diagnosed with Asperger syndrome, a PDD characterized by the narrow and focused analytical ability that often leads to brilliant accomplishment in computer and engineering fields.

"Many adults with autism are offended by the idea of a cure," Waltz said. She cites the work of Dr. Temple Grandin, and Jim Sinclair, author of Don't Mourn for Us. It's been proposed that Albert Einstein had autistic traits.

For anyone grappling with PDD, says Waltz, research and contact with others are essential. "There's a temptation to withdraw from the world and focus on your kid--you have to get out there and seek out other families. You quickly find out you can't do it on your own."