Severe Resistance to Weight Gain, Lack of Stored Triglycerides in Adipose Tissue, Hypoglycaemia, and Increased Energy Expenditure: A Novel Disorder of Energy Homeostasis

Background: Growth during childhood is a consequence of the equilibrium of energy balance. Obesity results from a shift of the equilibrium towards increased energy intake over expenditure. A clinical description of extreme leanness and failure to thrive secondary to a shift of the equilibrium towards increased energy expenditure over energy intake has not been previously described in the medical literature. Subjects and Methods: We report the case of a female child born premature with a birth weight of 1.1 kg who presented with extreme failure to thrive, persistent hypoglycaemia, paucity of fat in the adipose tissue with increased brown fat and increased resting energy expenditure. Results: Complete cessation of weight and height was noted between 3 months to 3.5 years of age. Hypoglycaemia was secondary to depleted energy stores and increased insulin sensitivity. Increased resting energy expenditure was demonstrated on indirect calorimetric assessment. Biopsy of adipose tissue demonstrated paucity of stored fat with increase in brown fat. No gain in weight and height was demonstrated despite high calorie intake of enteral and parenteral feeds. Conclusion: We describe a unique case of extreme failure to thrive with increased energy expenditure and severe hypoglycaemia. Unravelling the molecular basis of this novel disorder has the potential to provide insights into the prevention of obesity.