Singhal, Atul; (1997) Growth and metabolism in homozygous sickle cell disease. Doctoral thesis (M.D), UCL (University College London).

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Abstract

Growth impairment in homozygous sickle cell (SS) disease emerges as early as age six months but the mechanisms for this deficit are unknown. Analysis of longitudinal growth data suggested that adolescent growth and pubertal maturation of Jamaican SS children was delayed but final height was normal. This observation, delayed skeletal maturation, reduced weight for height, and lower subcutaneous fat reserves are consistent with the hypothesis that chronic childhood malnutrition retards growth in SS children. Competition from erythropoiesis may limit the availability of nutrients for growth and this hypothesis was supported by observations that high fetal haemoglobin levels, which reduce the haemolytic rate and therefore erythropoiesis, were associated with more normal growth, and that reducing erythropoiesis in SS patients with chronic hypersplenism by splenectomy was followed by an acceleration in linear growth. High erythropoietic activity may increase metabolism and the mean resting metabolic rate (RMR) relative to lean body mass of 16 post-pubertal SS adolescent boys was 22% greater than age and sex matched controls with a normal (AA) haemoglobin genotype. Adjusting for the higher visceral to somatic mass ratio of SS boys reduced the increase in RMR in SS disease to 8%. The RMR of prepubertal SS boys was also increased (relative to predicted values) but this increase did not correlate significantly with growth or serum transferrin receptor concentrations (a measure of erythropoietic activity). Faced with higher metabolic demands, SS patients have the option of increasing calorie intake or reducing energy expenditure for physical activity. The physical activity level of SS adolescent boys was 30% lower than age and sex matched AA controls suggesting that either the availability of calories or a poor appetite prevented an energy intake sufficient to maintain physical activity. It is therefore postulated that correction of suboptimal childhood nutrition could benefit the physical and mental development of children with SS disease.

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