The forced vital capacity of an 8-year-old child is significantly below the predicted normal value. There is no change following administration of albuterol via MDI. This would be most consistent with which of the following disorders?

• A. Asthma
• B. Bronchitis
• C. Cystic fibrosis
• D. Skeletal deformity

Answer: (D)

When you see a markedly reduced forced vital capacity that does not improve after a bronchodilator, think about a restrictive process rather than an obstructive one. The forced vital capacity measures the total amount of air you can exhale after a full inhale, so in restrictive conditions the lungs or chest wall can’t expand properly, leading to a lower FVC. A bronchodilator like albuterol works by relaxing airway smooth muscle and opening up narrowed airways, which typically helps in obstructive diseases such as asthma. In asthma, you’d expect at least some improvement in expiratory flow or volume after bronchodilation because the problem is reversible airway constriction. In contrast, conditions like skeletal deformity limit chest wall movement and reduce lung volumes directly; bronchodilators won’t restore those volumes because the limitation is mechanical, not due to airway caliber. Therefore, a significantly reduced FVC with no response to albuterol points to a restrictive issue such as skeletal deformity.