Why does my son behave so strangely?

My 9 yr old son has always been different.  He's very oppositional, hyperactive, lies, has an IEP in school, and most importantly...he defecates and urinates in strange places.  He has done this off and on for several years.  It started in heating vents when he was 5 or so.  It then progressed to inside toy boxes, backpacks, etc.  I just caught him this morning defecating in one of my 4 yr old daughter's tea pots.  She has started to copy a lot of her older brother's  behavior by urinating in her room in the closet.  I was a pediatric nurse in the past and never came across a behavior such as this.  He shows no signs, thank God, of violence toward animals or people, but I am concerned of his, and my family's long term welfare.  He is very disruptive to our household.  We have taken him to see a family doctor which prescribed Vyvanse, a stimulant to treat ADHD.  This helped some with his schoolwork and hyperactivity, but his thinking process was most definately the same.  What disorder does this sound like to you?   Thanks so much in advance for your time.

[Jessica L Thomason Sassi, Ph.D., BCBA-D]

Diagnostic criteria for Pervasive Developmental Disorders (including Autism, Aspergers, and others) include delays in social interaction skills, communication skills, and the presence of stereotyped or restricted behavior and interests.  Based on your brief description, it’s hard to know which, if any of these, diagnosis fits, and direct evaluation by a qualified professional is necessary for any diagnosis.  If you haven’t already brought this to the attention of your pediatrician, I’d recommend doing so now. Be sure to discuss both your behavioral/developmental concerns, as well as the toileting, specifically – apparent incontinence (or voiding in inappropriate places) can signal a medical issue such as a bladder infection or chronic bowel issue.
Regardless of his diagnosis, childhood behavior problems can typically be addressed through consultation with a Board-Certified Behavior Analyst.  This professional will want to spend time directly observing your child as well as interviewing your family, so that they can provide recommendations on how to best address the issue. A local BCBA can be found at the following site: http://www.bacb.com/consum_frame.html
Best of luck to you and your family