Pathologic similarities and differences between asthma and chronic obstructive pulmonary disease.

PURPOSE OF REVIEW: Classically, asthma and chronic obstructive pulmonary disease present distinct clinical, physiologic and pathologic features. However, not infrequently, patients may present with overlapping clinical symptoms and physiological abnormalities: patients with severe asthma may present with fixed airway obstruction and patients with chronic obstructive pulmonary disease may have hyperresponsiveness and eosinophilia. At pathological level, inflammatory and structural similarities also occur and may be related to the phenotypic overlaps.

RECENT FINDINGS: In patients with asthma overlaps at inflammatory level exist with chronic obstructive pulmonary disease, such as increased neutrophilia in patients with severe asthma or an association of CD8+ T cells and lung-function decline. In chronic obstructive pulmonary disease, minimizing eosinophilia may be important to reduce exacerbations. Structural alterations occur in both diseases, but involving airway compartments differently. Airway epithelial changes, extracellular matrix deposition and mucus gland hypertrophy occur in both diseases. Asthmatics have thicker reticular basement membrane and more prominent smooth-muscle abnormalities, whereas emphysema is a distinct feature of chronic obstructive pulmonary disease.

SUMMARY: Recognizing the differences and similarities at pathological level in both diseases may lead to a better understanding of the overlapping clinical and physiological phenotypes, thereby helping to better plan specific treatment and long-term management.