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The Overlap Between Respiratory Bronchiolitis and Desquamative Interstitial Pneumonia: Results Summary of the Two Index Cases

Correlations between the extent of RB/DIP-like changes (0 to 100% involvement of biopsy) and total pack-years smoked was performed using linear regression analysis and the Pearson correlation coefficient. Similarly, correlations between the extent of RB/DIP-like changes and pulmonary function variables total lung capacity [TLC], FEV1, and diffusion capacity of the lung for carbon monoxide [Dlco] was performed by linear regression and the Pearson correlation coefficient. Statistical analysis was performed using JMP software, version 4 (SAS Institute, Cary, NC) with p values < 0.05 considered statistically significant.
The first patient was a 52-year-old white woman (patient 1 in Tables 1, 2) with a 70 -pack-year smoking history referred for evaluation of dyspnea and cough. review
The pulmonary examination revealed bilateral end-inspiratory basal crackles. Pulmonary function testing revealed restriction, with a plethys-mographically measured TLC of 70% predicted and a Dlco of 48% predicted (Table 1). Chest HRCT demonstrated extensive areas of ground-glass attenuation bilaterally, most marked in the middle and upper lungs (Fig 1, top). Tiny nodules were appreciated in the middle and upper lung zones. The provisional clinical diagnoses were of hypersensitivity pneumonitis, RB-ILD, or DIP. A videothoracoscopic biopsy of the right lower lobe demonstrated typical lesions of PLCH (detection of Langerhans cells confirmed by S-100 and CD1a immunostain-ing) associated with a marked DIP-like reaction in the surrounding lung parenchyma (Fig 1, center and bottom). In spite of repeated attempts at smoking cessation, the patient was unable to quit, and did not appreciate any benefit from a trial of oral prednisone. In spite of continued smoking, her lung function stabilized and the patient declined any further specific therapy for her lung disease.
Fig1
Figure 1. Top: HRCT of the first index patient showing bilateral areas of ground-glass attenuation with scattered nodules. Center: Scanning power microscopy shows diffuse moderate airspace filling by macrophages with patchy mild interstitial widening without definite nodules (hematoxylin-eosin). Bottom: Higher-power detail shows marked airspace filling by macrophages that have a faint tan pigmentation typical of smokers. The alveolar septa are widened with somewhat hyalinized eosinophilic-appearing fibrous tissue (hematoxylin-eosin).
Table 1—Summary of Smoking Histories, Histopathologic Findings, and Pulmonary Function Testing

Patient No./ Gender* SmokingHistory,

Pack-yr

Currentvs Former Smokers f rb/dipExtent, % Alveolar Septal Fibrosis Extent, % Cystic Change, 0 to 3 Score Emphysema % Tissue Involved Pulmonary Function Test{
1/female 70 Current 80 60 0 10 Restrictive
2/male 30 Former 70 10 0 10 Restrictive
3/female 15 Current 70 10 1 60 Normal
4/male NA Current 70 90 1 80 Restrictive
5/female 60 Current 60 50 0 50 Obstructive
6/male 25 Current 60 0 0 40 Obstructive
7/female 25 Current 50 0 1 20 Normal
8/female 20 Current 30 10 1 20 Normal
9/male 30 Current 30 10 0 10 Restrictive
10/male 15 Former 20 10 1 10 Restrictive
11/female 15 Former 20 10 3 60 Obstructive
12/female 37 Former 20 50 1 30 Restrictive
13/female 1 Former 10 0 0 0 Restrictive
14/male 2 Former 10 0 2 30 Obstructive

Table 2—HRCT Findings

Patient No./ Gender* Nodules, 0 to 3 Score Cysts, 0 to 3 Score Adenopathyf Ground-Glass Attenuation f Emphysemaf Impression of Original Reader{
1/female 1 0 + + 0 HP
2/male 1 0 + + 0 HP
3/female 2 2 0 0 0 PLCH
4/male 0 3 + 0 0 PLCH
5/female 1 3 0 0 0 PLCH
6/male 2 0 0 0 + Nonspecific
7/female 1 1 0 0 0 PLCH
8/female 1 0 0 0 0 BOOP
9/male 1 2 0 0 0 PLCH
10/male 1 0 0 + 0 Nonspecific
11/female 2 0 0 0 0 PLCH
12/female 0 3 0 0 0 Nonspecific
13/female 1 2 0 0 + PLCH
14/male 0 1 0 0 0 PLCH