Confirmed beta16 Arg/Arg polymorphism in a patient with uncontrolled asthma

To report a case of confirmed beta(16) Arg/Arg polymorphism (Arg/Arg) in a patient with uncontrolled asthma.

A 49-year-old black female presented to the emergency department with acute shortness of breath with subsequent intubation. After extubation, she reported multiple hospitalizations for asthma with one prior intubation, adherence to asthma medications, and very frequent use of her short-acting beta(2)-agonist (SABA). Because of her asthma history, self-reported adherence, and race, she was tested for beta(2)-adrenoreceptor genotype, which revealed Arg/Arg. Based on these findings, beta(2)-agonists were discontinued and tiotropium (maintenance) and ipratropium (primary rescue) were initiated as part of her asthma regimen. Application of the Naranjo probability scale revealed probable causality between uncontrolled asthma in our patient and SABA use. The patient is followed in our outpatient pulmonary clinic and, at time of writing, had not been admitted to our hospital for asthma-related events.

Approximately 15% of Americans with asthma are Arg/Arg, with an increased prevalence in black and Asian populations. It is hypothesized that changes in the degree of sensitivity or desensitization to the bronchodilator effect of beta(2)-agonists may occur in these individuals. Data exist, although they are conflicting, suggesting that inhaled beta(2)-agonists may worsen clinical outcomes. Trials have reported declines in peak expiratory flow rates plus increases in asthma symptoms and exacerbations when SABAs have been used regularly in patients with Arg/Arg. Studies evaluating long-acting beta(2)-agonists (LABAs) have inconsistent results. Preliminary data suggest that anticholinergics may serve as a beneficial primary rescue medication instead of beta(2)-agonists in patients with Arg/Arg.

Clinicians should be aware of factors (eg, race and polymorphisms) that may predict unfavorable outcomes with regular SABA and possibly LABA use. Patients with poor asthma control despite adherence to asthma therapy may benefit from beta(2)-adrenoreceptor genotyping and, possibly, from anticholinergics.