Energy metabolism in cystic fibrosis.

Cystic fibrosis (CF) remains a major cause of refractory malnutrition in clinical practice. It is clinically and genetically a heterogeneous disorder, and energy metabolism, as with other manifestations of the disease, is subject to wide variability. Differences in metabolic needs are related to the specific CF genotype, and are the result of a complex interaction of physiological, environmental and genetic variables. Based on the recognition of malnutrition as a major prognostic factor adversely affecting survival, the achievement and maintenance of energy balance in CF is one of the central aims of management. Despite advances in pancreatic supplements and aggressive nutritional support, however, growth retardation of affected children and wasting of CF adults remains a major clinical problem, evidence of our incomplete understanding of the mechanisms and management of metabolism in the disease. The prevalence of CF, approximately 5000 in 1985 (British Paediatric Association Working Party on Cystic Fibrosis, 1988), is increasing every year, the increased numbers almost entirely being accounted for by patients over 15 years old. The evolving natural course of CF as it becomes a condition of adulthood, provides a further source of variation in defining and meeting the metabolic needs of CF patients. This enlarging population includes an increasing number of adults, a proportion of whom have undergone heart-lung transplant and in whom regulation of metabolism may be related to survival, and also includes presymptomatic infants identified by newborn screening, in whom the importance of adequate nutrition is apparent from the deficits in body composition.