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

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).

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.

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, FEF(25-75): -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).

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.