List the odd one out among the following: (A) Trisomy 18 (Noonan syndrome), (B) Trisomy 21 (Downs syndrome), (C) Trisomy 18 (Edwards synd.), (D) Trisomy 13 (Patau synd.)
Answer is A. Trisomy 18 is Edward syndrome & not Noonan syndrome. Noonan syndrome occurs in both males and females with a normal karyotype(46,XX and 46,XY). Refer to the image below.