High functioning autism and childhood disintegrative disorder in half brothers

Childhood Disintegrative Disorder (CDD) is grouped with autism as a subtype of Pervasive Developmental Disorder (PDD) in ICD-10 and DSM-IV. This is th e first report of autism and CDD cosegregating within a sibship. J. P. and M. P. are half-brothers with the same mother. J. P. is an 18-year-old with impairments in communication, social reciprocity, and stereotypies and was diagnosed with autism. M. P. is a 7-year-old who developed normally to 2 ye ars 4 months. He then underwent a profound regression, becoming nonverbal a nd socially withdrawn, and lost adaptive skills. Investigations did not rev eal any neurodegenerative process. M. P. was diagnosed with CDD. The rarity of the two conditions suggests a shared transmissible mechanism. The impli cations for autism/PDD genetic studies are discussed.