Table 1.

Reported Clinical Differences in Genetic Subtypes of Prader-Willi Syndrome

Genetic defect	Characteristics
Typical 15q11-q13 deletion	Hypopigmentation and more homogenous clinical findings including a typical facial appearance; more self-injurious behavior (skin picking); higher pain threshold; greater jigsaw puzzle skills than seen in maternal disomy
Type I deletion	Increased maladaptive and compulsive behavior relative to Type II deletion and maternal disomy; poorer academic performance relative to Type II deletion and maternal disomy
Type II deletion	Better adaptive behavior and social skills relative to Type I or maternal disomy
Maternal disomy 15	Higher verbal IQ scores; greater numeric calculation skills, superior visual memory, poorer object assembly and visual perceptual skills; increased psychosis relative to typical deletion