Lung disease is a major cause of morbidity and mortality in patients with sickle cell disease. Acute chest syndrome caused by lung infections, infarction or fat embolism occurs in nearly one half of patients with sickle cell disease. The presence of airway hyperreactivity may be a silent comorbid factor for pulmonary disease in patients with sickle cell disease. Leong and colleagues conducted a study to determine the presence of airway hyperreactivity in children with sickle cell disease and to assess if airway hyperreactivity can exist in these children even without clinical symptoms.

Forty asymptomatic children with sickle cell disease, ranging from six to 19 years of age, were included in the study. Thirty patients had homozygous SS disease, seven patients had sickle-C disease and three patients had sickle-beta⁺-thalassemia, as diagnosed by hemoglobin electrophoresis. The patients were divided into two groups. Eighteen patients had a history consistent with reactive airway disease, characterized as recurrent wheezing that improved with bronchodilator therapy. Twenty-two patients had no symptoms consistent with reactive airway disease. Ten healthy children were also included in the study as a control group. Baseline pulmonary function tests were performed on all participants. If the baseline forced expiratory volume in one second (FEV₁) was less than 70 percent and there was at least a 12 percent increase following bronchodilator therapy, the child was said to have airway hyperreactivity. If the baseline FEV₁ was greater than 70 percent, airway hyperreactivity was determined by cold-air challenge. Children who had a decrease in FEV₁ from baseline of greater than 10 percent were said to have airway hyperreactivity.

Eighty-three percent of patients in the group with a history consistent with reactive airway disease and 64 percent of patients in the group without symptoms of reactive airway disease had evidence of airway hyperreactivity, for an overall prevalence rate of 73 percent. This is much higher than the estimated 6 percent prevalence rate found in the general population. Airway hyperreactivity frequently leads to ventilation-perfusion mismatch and, consequently, to hypoxia or acidosis. This could result in vaso-occlusive painful episodes.

The authors conclude that there is a high prevalence of airway hyperreactivity in patients with sickle cell disease, in patients both with and without a history of reactive airway disease. Greater effort should be made to recognize and appropriately treat reactive airway disease in this population.