Familial factors influence level of functioning in pervasive developmental disorder.
OBJECTIVE
To determine whether siblings with pervasive developmental disorders (PDD) tend to have the same type and number of PDD symptoms or a similar level of functioning.


METHODS
The familial correlations for PDD subtype, symptom totals, adaptive behaviors, and nonverbal IQ were calculated for 94 children with PDD from 46 families.


RESULTS
On variables measuring PDD symptoms, only impairments in nonverbal communication and verbal/nonverbal status tended to run true within families. There was no familial aggregation of PDD subtype. In contrast, measures of nonverbal IQ and adaptive behaviors in socialization and communication showed a moderate degree of familial resemblance. The degree of familial resemblance did not change if the analysis was restricted only to those families in which both affected children met criteria for autism.


CONCLUSIONS
Insofar as the familial resemblance seen in PDD is due to genetic factors, these data provide some evidence that higher- and lower-functioning PDD children may arise from separate genetic mechanisms. Current gene-mapping studies of PDD may need to take this evidence of genetic heterogeneity into account.
MacLean
J E
JE
Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada.
Szatmari
P
P
Jones
M B
MB
Bryson
S E
SE
Mahoney
W J
WJ
Bartolucci
G
G
Tuff
L
L
D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001526:Behavioral Symptoms / Q000145:classification / Q000209:etiology; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000145:classification / Q000209:etiology; D002675:Child, Preschool; D004198:Disease Susceptibility / Q000209:etiology; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D016555:Matched-Pair Analysis; D009679:Nuclear Family; D012720:Severity of Illness Index