We all know how infants can act up during their terrible twos, but when these behaviors are accompanied by developmental setbacks, they could point to something more serious.

Researchers are currently learning more about regressive autistic spectrum disorder (RASD), which describes children who have been diagnosed with autism who demonstrate a history of a regression. The regression refers to a marked loss of previously acquired developmental skills such as language or social ability.

"Often children with regression aren't being seen by professionals at the time of the loss of skills. The parents are aware of a problem, but not sure what it is so they don't seek medical or psychological help until the symptoms persist for over a year," said Gerry A. Stefanatos, D.Phil., an associate professor in the department of Communication Sciences and Disorders at Temple University.

Stefanatos writes about RASD and the growing research into this disorder in the December issue of Neuropsychology Review. He estimates RASD comprises about 25 to 30 percent of the population of children eventually diagnosed with an autistic disorder.

Children with RASD seem to develop normally until about 18-24 months. At that point they have acquired small vocabulary and act social, but then over the course of weeks or months, they lose their speech and no longer use words they had previously learned. They have problems comprehending speech they used to understand and no longer follow commands.

"One of the more obvious cues for parents is if the child no longer responds to his or her own name. Often times this is accompanied by deterioration in behavior. They child can become irritable, prone to tantrums," Stefanatos said.

Information about regression is commonly obtained retrospectively many months to years after the symptoms began. Due to the unclear onset time and prolonged time course that characterizes the regression in many cases, it's difficult for parents to remember when their child was no longer using words previously elicited frequently with meaning at an earlier stage of development.

"If you have suspicions, go and see a pediatrician and explain what you're seeing in your child. If there is in fact a regression, it helps to have another set of eyes to confirm suspicions. You may also want to seek out a specialist in autism to assist with diagnoses," Stefanatos said. "When continuously living with a child, it's often difficult to see the subtle changes over time."

When Stefanatos works with parents, he frequently asks them to provide video of the child at various points in development (birthdays, holidays) to determine the history of the potential disorder. The videos can show the child engaged with people and yet a year later, show that same child with serious withdrawal.

Among the many potential causes of regression, Stefanatos said health care providers or autism specialists who suspect RASD should look for evidence of an electroencephalographic (EEG) abnormality, which might suggest an epileptic or seizure disorder. An EEG measures electrical activity produced by the brain and is recorded from electrodes placed on the scalp. 

Seizure-related brain activity can act like "electrical noise" and interfere with the function of areas of the brain responsible for different areas of development. This noise can potentially be disruptive to the wiring of connections between brain cells developing at that stage. In these cases, medications may reduce disruptive electrical discharges so they don't have a negative influence on neurological development. 

"When it's treated, either behaviorally or medically, there can be a significant improvement in behavior and development. This is one reason why it's important to identify RASD as early as possible," he said.

More research is required to explore the similarities and differences between RASD and ASD. In the meantime, it's important for parents and health care providers to pay attention to any lost developmental milestones. 

"Be very attentive to that aspect of child's history and act accordingly; take it very seriously. It (regression) can be a red light that something is amiss with a child's development and the issue needs to be looked at in more detail," Stefanatos said.