Lower respiratory tract infections are one of the leading causes of mortality worldwide. Among these, one of the most prominent is pneumonia, a term used to define any lung infection.^[3] The clinical presentation may be acute, characterized by symptoms such as fever, cough, shortness of breath, and a decline in general health, or chronic, with a more prolonged course.^[4]

Thus, the present study aimed to analyze the morphological patterns of types of lung infections in autopsy cases within the death verification service (DVS) and establish associations between clinical conditions, comorbidities, and risk factors that patients presented with at the time of death.

Material and Methods

Cases were included in the study when autopsies revealed evidence of lung infections in the necroscopic examination. The clinical and laboratory results were evaluated using autopsy records. All histological slides of necroscopic cases selected for material suitability were reviewed.

Data regarding age, sex, clinical course (diabetes, hypertension, dyslipidemia, obesity, smoking, alcoholism, cachexia, allergies, autoimmune diseases, and other lung pathologies, such as pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), clinical history of immobility/bed restriction, hospitalization, institutionalization, oncological history, previous surgeries, immunodeficiencies, and vaccination).

Autopsy samples of lung infections were examined under an optical microscope, and pulmonary findings are described in Table 1. The collected data were separated into categorical variables by epidemiological profiles and histopathological patterns found in the microscopic analyses of the sample.

Statistical analyses were performed using Statistical Package for Social Sciences (SPSS) version 21 (IBM Corp., Armonk, NY, USA). Qualitative data are presented as frequencies and percentages. Independent t-tests were performed to compare continuous variables between groups, and the results are presented as measures of central tendency (average ± standard deviation and median). The Chi-square test was used to compare categorical variables. Statistical significance was defined as P< 0.05. Histological findings were represented as categorical variables, and bivariate associations were estimated using simple linear regressions with Poisson responses for outcomes and binary or normal responses for numeric outcomes. The variables that presented an association with p < 0.20 were taken to adjust a multiple regression with Poisson or normal response. Statistical significance was defined as P < 0.05.

The study was reviewed and approved by the ethics committee (CAAE:71548923.2.0000.5411).

Results

A total of 165 autopsy reports of patients who died of pneumonia between 2010 and 2023 were analyzed.

Regarding the epidemiological information on the number of autopsy cases studied, we extracted the following profile extracted from the necropsy reports (data from deceased patients): male patients 61.81%, female patients 38.18 %, white ethnicity 36.70%, brown ethnicity 7.78%, black ethnicity 2.22%, ethnicity not reported in the reports 53.3%, occupational exposure in 2.22% with an average age of 60.5 years, smoking in 20% of cases with an average age of 61.38 years, alcoholism in 23.33% of cases with an average age of 52.19 years.

Presence of comorbidities such as diabetes mellitus in 14.44% of cases, with a mean age of 61.38 years, systemic arterial hypertension 35.56% with a mean age of 66.65 years, dyslipidemia in 6.67% of cases with a mean age of 73.33 years, obesity in 8.89% of cases with a mean age of 50.12 years.

Non-pulmonary neoplasms were identified in 15.56% of cases with a mean age of 68.28 years, cachexia in 24.44% of cases with a mean age of 52.64 years, immunodeficiencies not related to the HIV were observed in 5.56% of cases with a mean age of 43.80 years, autoimmune diseases observed in 4.44% of cases with a mean age of 42.75 years, patients seropositive for human immunodeficiency virus in 7.78% of cases with a mean age of 42.71 years.

Patients with pneumonia who also had diseases at a primary pulmonary site: presence of chronic obstructive pulmonary disease (COPD) in 8.89% of cases with a mean age of 69.50 years, idiopathic pulmonary fibrosis in 1.11% with a mean age of 94.0 years, pulmonary hypertension in 12.22% of cases with a mean age of 56.97 years, and some type of lung carcinoma in 5.56% of cases with a mean age of 61.40 years.

Patients who were selected for this case series and still presented complications such as: acute kidney injury in 14.44% of cases with a mean age of 33.14 years, chronic kidney disease in 3.33% of cases with a mean age of 77.66 years, acute respiratory distress syndrome in 5.56% of cases with a mean age of 44.00 years, pulmonary thromboembolism in 10.00% of cases with a mean age of 63.77 years, sepsis in 41.11% of cases with a mean age of 42.49 years, use of supplemental oxygen in 7.78% of cases with a mean age of 57.57 years and with care in an intensive care unit (ICU) in 20.00% of cases with a mean age of 32.37 years.

Patients who were confined to bed in the postoperative period, with a late surgical history, or institutionalized, totaled 31.11% with a mean age of 57.45 years. Prematurity was observed in 3.33% of cases, and congenital malformations in 2.22% of cases.

All histological criteria studied in the necropsy cases are listed in Table 1, with the number and percentage of cases, respectively, for the 165 autopsies studied.

Table 1: Description of the spectrum of histological changes in pulmonary infections from reviewed autopsy cases

After all the clinical and morphological criteria were reviewed, the data were submitted for statistical analysis. The morphological data were grouped and named with letters in a sequential pattern, forming morphological groups.

Composition of group A: Tracheitis, bronchitis, luminal and lamina propria lymphocytic bronchiolitis, bronchiectasis, and bronchiolectasis. Results for group A: Chronic obstructive pulmonary disease (COPD) was significantly associated with an increase in the number of events (p = 0.017). Diabetes Mellitus was significantly associated with a reduction in the number of events in Group A (p = 0.031). Systemic arterial hypertension was significantly associated with a reduction in the number of events in Group A (p = 0.039).

Composition of group B: Type I and type II pneumocyte hyperplasia, alveolitis, perialveolar capillaritis, and alveolar thickening. Results for group B: Linear regression showed that smoking was significantly associated with a reduction in the number of events in group B (p = 0.009). Chronic obstructive pulmonary disease (COPD) was significantly associated with a reduction in the number of events in group B (p = 0.015).

Composition of group C: Condensation, congestion, and pulmonary edema. Results for group C: In the linear regression, male sex was significantly associated with an increase in the number of events in group C (p = 0.041). Obesity was significantly associated with an increase in the number of events in Group C (p = 0.043). Sepsis and septic shock were significantly associated with an increase in the number of events in Group C (p = 0.027).

Group D: Neutrophilic and lymphomononuclear inflammatory patterns with interstitial and alveolar distribution, interstitial and alveolar xanthomatous cells, bronchopneumonia, and lobar pneumonia. Results for group D: In linear regression analysis, chronic obstructive pulmonary disease (COPD) was significantly associated with a reduction in the number of events in group D (p = 0.017).

Group E: Atelectasis, granuloma, cavitation, abscess, pulmonary infarction, pulmonary necrosis, caseous necrosis, and scar area. Results for group E: Smoking was significantly associated with an increased number of events in group E (p = 0.035). Chronic obstructive pulmonary disease (COPD) was significantly associated with an increased number of events in group E (P= 0.007). Pulmonary hypertension was significantly associated with an increased number of events in group E (p = 0.049).

Group G included pleural effusion, empyema, acute suppurative pleuritis, fibrinous pleuritis, chronic pleuritis, pleural adhesion, pleural thickening, and cisuritis. Results for group G: In linear regression analysis, diabetes mellitus was significantly associated with an increase in the number of events in group G (p = 0.048). Acute kidney injury was significantly associated with an increase in the number of events in group G (p = 0.006).

Composition of group K: Alveolar emphysema and blisters. Results for group K: Systemic arterial hypertension was significantly associated with an increased occurrence in group K (p = 0.036).

Group L: Alveolar bronchiolization, lymphoid clusters in the lamina propria, mediastinal or peribronchial lymph node enlargement, and metaplasia. Results for group L: There were no associations between variables in linear or multiple regression for outcome group L.

Composition of group M: Lung neoplasia and metastases. Results for group M: Linear regression showed that smoking was significantly associated with an increased occurrence in group M (p = 0.001). Systemic arterial hypertension was significantly associated with an increased occurrence in group M (p = 0.040).

Composition of group N: Presence of food debris. Results for group N: In linear regression, bronchial asthma was significantly associated with an increased occurrence in group N (RP = 5.09; p = 0.026). Cachexia was significantly associated with an increased occurrence in group N (p = 0.001).

Composition of group P: anthracosis, alveolar and interstitial xanthomatous macrophages, and alveolar emphysema, as represented in Figure 1.

Figure 1: Histological group “P”. 1A: Pulmonary anthracosis (arrow) (H&E: 400X magnification), 1B: alveolar xanthomatous macrophages (arrow) (H&E: 400X magnification), 1C: alveolar emphx’ysema (arrow) (H&E: 400X magnification) and 1D: interstitial xanthomatous macrophages (H&E: 400X magnification).

Results for group P: In the linear regression, the 1-year difference between ages was significantly associated with an increased number of events in group P (p < 0.001) (Table 2). Male sex was significantly associated with an increased number of events in the P group (p = 0.018) (Table 2). Diabetes mellitus was significantly associated with an increase in the number of events in group P (P = 0.032) (Table 2).

Table 2: Study of frequency associations between the histopathological group “P” (pulmonary anthracosis, interstitial xanthomatous macrophages, alveolar xanthomatous macrophages and alveolar emphysema) and risk factors for Pneumonia.

*p was set at p< 0.05.

Composition of groups: F (blisters, interstitial and alveolar fibrosis), H (diffuse alveolar damage, fibrin in the airways, thrombi, or emboli), I (pulmonary hemorrhage and blood in the airways), J (hemosiderin pigments and anthracosis), O (bacterial colonies, viral nuclear inclusions, fungal elements, and staining for acid-fast bacilli). There were no associations between variables in the linear or multiple regression for the outcomes of these groups.