Successful methylphenidate treatment of early onset extreme obesity in a child with a melanocortin-4 receptor gene mutation and attention deficit/hyperactivity disorder.

We present the case report of a 2 year old boy with early onset extreme obesity (body mass index (BMI) 34.2 kg/m²; body mass index standard deviation score (BMI-SDS) 5.4) who is heterozygous for a non-conservative functionally relevant melanocortin MC(4)receptor mutation (Glu308Lys) and who also showed severe symptoms of attention deficit/hyperactivity disorder (ADHD). Treatment with the stimulant methylphenidate led to a sharp decrease of BMI to 21.8 kg/m² (BMI-SDS 2.8) within 24 months. We discuss potential mechanisms for this unusually large weight loss and suggest a potential link between the melanocortinergic and the dopaminergic systems, and the sympathetic nervous system. The potential benefit of methylphenidate in obese melanocortin MC(4)receptor mutation carriers with and without co-morbid ADHD warrants further studies.