TABLE 1

Studies of structural epithelial alterations in mild, moderate, severe and fatal asthma

MethodsPopulationFindings[Ref.]
Post mortem specimen: large and small airways (not defined)Fatal asthma (n=20)Occluding (mucus) plugs were seen in all small bronchi
Epithelial cell shedding was observed in medium-sized bronchi#
[16]
Post mortem specimen: segmental and lobar bronchi (Pbm 10>18 mm); subsegmental bronchi (4–10 mm); small and large membranous bronchioles (Pbm <2–4 mm)Fatal asthma (n=11)
Nonfatal asthma (n=13)
Control (n=11)
Greater mucus gland area in airways (4–10 mm) in fatal asthma compared to controls
No difference in percentage of basement membrane covered with normal, damaged or desquamated epithelium between fatal asthma, nonfatal asthma and controls
[21]
Case report on lung biopsy samples and post mortem specimen: large and small airways (not defined)Paediatric fatal asthma (n=2)
Paediatric asthma in remission (n=2)
In airways >1 mm from patients with asthma in remission mucus plugging, goblet cell hyperplasia and basement membrane thickening was observed; detachment of the epithelial lining was not observed
In airways <1 mm from patients with asthma in remission occasional mucus plugs were observed but no goblet cell hyperplasia
In the post mortem specimens from patients with fatal asthma similar alterations were observed but more prominent
[22]
Post mortem specimen: large airways (presence of cartilage) and small airways (no presence of cartilage)Asthma (n=8), of which three were fatal asthma
Chronic bronchitis (n=6)
Control (n=4)
Significantly more mucus in asthma and chronic bronchitis group than in control group
Hypertrophy/hyperplasia of mucous glands and goblet cells in both asthma and chronic bronchitis, with marked hyperplasia of goblet cells in the airways from fatal asthma patients
More goblet cells in asthma and chronic bronchitis than in control group but not significant
[32]
Post mortem specimen: large and small airways (not defined)Fatal asthma (n=93)
Control (n=6)
Airways of patients with fatal asthma were more frequently occluded by mucus and cells
A greater proportion of cells was present in exudate in the small airways than in larger airways of patients with fatal asthma
[33]
Post mortem specimen: large airways (presence of cartilage) and small airways (no presence of cartilage and <0.4 mm diameter)Fatal asthma (n=12)
Control (n=8)
Increased amount of mucus in fatal asthma in comparison to controls
Reticular basement membrane significantly increased in fatal asthma cases compared with controls
Median outer luminal diameter was 2mm of large airways and <0.3 mm in small airways
[34]
Post mortem specimen: large airways (presence of cartilage) and small airways (no presence of cartilage)Fatal asthma (n=3)
Nonfatal asthma (n=5)
Control (n=4)
Increased amount of mucus in fatal asthma compared to nonfatal asthma and controls
Increased amount of mucus in nonfatal asthma compared to controls
Increased amount of goblet cells in fatal asthma compared to nonfatal asthma and controls
Epithelial thickness in fatal asthma group was higher than in the nonfatal asthma and control group
[36]
Lung biopsy specimen obtained through VATS: large and small airways (not defined)Severe asthma clinically, with diagnosis of asthmatic granulomatosis (n=10) after histologic evaluationPapillary epithelial hyperplasia, basal cell hyperplasia and goblet cell metaplasia was observed in all cases
Mucus plugging was observed in eight out of 10 cases
Subepithelial basement membrane thickening was seen in all cases
[37]
Lung biopsy specimen obtained through VATS: small airways (airways ≤2 mm in size and no presence of cartilage)Severe asthma (n=29) subdivided into four groups: 1) severe asthma; 2) severe asthma with autoimmune disease; 3) severe asthma with asthmatic granulomatosis; and 4) severe asthma with asthmatic granulomatosis and autoimmune diseaseMucus plugging and goblet cell metaplasia was observed in 20 cases, in cases of severe asthma with asthmatic granulomatosis and autoimmune disease this was observed less frequently than in the other subgroups[38]
Post mortem specimen: small airways (<2 mm in size and no presence of cartilage)Fatal asthma (n=6)
Control (n=6)
Degree of lumen occlusion observed in all subjects with fatal asthma was significantly higher than controls[40]

Findings for small airways are presented. Pbm: basement membrane perimeter; VATS: video-assisted thoracoscopy. #: it is unclear whether this is observed in small or large airways.