PROXIMAL 15q DELETION IN A FATHER AND SON WITH ISOLATED OBESITY

The Prader Willi Syndrome (PWS) has been described clinically as: obesity, hypotonia, acromicria, and mental retardation. The eating disorder is currently thought to have a hypothalamic basis. Recent reports have associated PWS with a deletion between bands q11 and q13 on chromosome 15. Studies of PWS patients with interstitial deletion frequently show the origin of the deleted chromosome to be paternal, although parental chromosomes have been normal. We are reporting an 8 year old boy with isolated obesity and the karyotype: mos46XY, 46XYdel(15)(q11.1 q11.2). History revealed normal developmental milestones. Height was 90%ile, weight >95%ile, and head circumference 90%ile. No dysmorphic features were noted. Hand length was at the 75%ile. He had normal tone and normal genitalia. The patient's father reported obesity in adolescence with a maximum weight of 102kg (>95%ile); height was 170cm (10%ile). His obesity resolved with strict dietary management starting at 22 years of age. He has normal intelligence, no dysmorphic features, and is the father of two children. His karyotype: mos46XY, 46XYdel(15)(q11.1 q11.2). Both father and son had approximately 60% normal cells and 40% deleted cells (lymphocyte culture). Neither father nor son has features of PWS other than obesity. We raise the possibility that the hypothalamic control of obesity is mediated at the q11.1-q11.2 region of the 15 chromosome. This deletion can be associated with isolated obesity as well as PWS.