Lung function and somatic growth in patients with hemoglobin SC sickle cell disease

Objective: To investigate the changes in lung function and somatic growth that occur over time in children with hemoglobin SC (Hb-SC) sickle cell disease (SCD). Methods: Measurements of lung function and somatic growth were performed in patients with Hb-SC twice with an interval of 50.2 +/- 26.0 months. Comparisons were made with a group of patients with hemoglobin SS (Hb-SS) SCD, matched by age, race, and gender who underwent similar testing and served as controls. Results: Indices of lung function in patients with Hb-SC were and remained within the normal range in the two testing periods and they were significantly higher than those measured among patients with Hb-SS. However, there was significant and similar decline (as percentage from baseline) over time in both groups (forced vital capacity, FVC: -3.7 +/- 9.4 vs. -3.8 +/- 14.2; forced expiratory volume in the first second, FEV1: -7.4 +/- 9.3 vs. -6.8 +/- 15.2; forced expiratory flow at 25-75% of FVC, FEF25-75: -13.7 +/- 20.6 vs. -12.1 +/- 24.7 for Hb-SC and Hb-SS respectively). The body mass index (BMI, percentile) was significantly (P<0.05) higher among patients with Hb-SC (49 +/- 36 vs. 26 +/- 18) and increased over time in both groups (50 +/- 33 vs. 32 +/- 31). Conclusion: Lung function is generally normal among children with Hb-SC, but it declines over time in a fashion similar to that observed among patients with Hb-SS SCD. The decline is slow and it is not associated with changes in somatic growth. Our findings suggest that patients with Hb-SC should probably have the same close follow-up as patients with Hb-SS.