Splenic Silicosis Accompanying Chronic Complicated Silicosis: A Rare Systemic Manifestation of Silica Exposure – A Case Report

Abstract

Silicosis is an occupational pulmonary disease caused by prolonged inhalation of crystalline silica particles. Although it predominantly affects thoracic structures, extrapulmonary or systemic manifestations are rare. We report a 60-year-old male who worked as a grinder in a quartz mill for 7 years and presented with advanced dyspnea and chronic cough. Imaging revealed bilateral progressive massive fibrosis and radiodense nodules in the spleen. Splenic involvement, also known as splenic silicosis, is an exceptionally rare entity and was detected incidentally during radiological evaluation. This case highlights the potential for systemic dissemination of silica particles and contributes to the limited literature on extrapulmonary silicosis.

INTRODUCTION

Silicosis is an incurable but preventable occupational lung disease that leads to irreversible, progressive fibrosis and causes significant morbidity and mortality.[1] Since 1995, the World Health Organization has been promoting global efforts to eliminate silicosis by 2030; however, the disease remains a prevalent occupational health issue, especially in low- and middle-income countries. According to the 2016 Global Burden of Disease Study, silicosis accounts for approximately 10,400 deaths and 210,000 years of life lost annually.[2]

While calcified silicotic nodules in the lungs and eggshell calcifications of the hilar lymph nodes are well-recognized, involvement of extrathoracic organs is rare.[3] Inhaled silica particles can disseminate to extrapulmonary tissues—such as the liver, kidneys, spleen, and extrathoracic lymph nodes—via lymphohematogenous routes.[4] Crystalline silica exposure has also been implicated in the development of autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, and glomerulonephritis.[1]

Splenic lesions detected on computed tomography (CT) are generally benign; most calcified splenic lesions are considered sequelae of prior granulomatous infections. Notably, silica particles can form a multinodular pattern in organs like the spleen, resembling that seen in the lung parenchyma.[5] Therefore, it is important to perform a differential diagnosis to distinguish granulomatous diseases such as tuberculosis, histoplasmosis, and sarcoidosis, which can present with similar radiologic findings.[3]

In this report, we present a rare case of splenic silicosis, indicating splenic involvement in silicosis, detected radiologically in a patient with chronic complicated silicosis. Reporting such rare cases contributes to a better understanding of the disease spectrum and aids in accurate diagnosis and management.

CASE REPORT

A 60-year-old male patient presented to the emergency department with progressive exertional dyspnea and a dry cough over the past few months. He denied fever, weight loss, chest pain, or hemoptysis. He had been hospitalized twice within the previous year for similar respiratory complaints.

A detailed occupational history revealed that he worked as a manual laborer in a quartz mill from 1983 to 1990. His duties included shoveling stone fragments—previously broken down by a compressor—into a grinding machine and transferring the resulting sand-like material to a filtration unit. Crystalline sand and fine dust were collected in separate sacks. He worked in an enclosed, unventilated environment without respiratory protection.

He was a former smoker with a 15-pack-year history. On examination, his respiratory rate was 22 breaths/min, blood pressure 110/70 mmHg, heart rate 92 bpm with regular rhythm, and oxygen saturation 88% on room air. Auscultation revealed bilateral inspiratory crackles without pleural effusion. Laboratory tests showed normal liver and kidney function, with an elevated C-reactive protein of 59 mg/L; other parameters were within normal limits.

Posteroanterior chest radiography demonstrated opacities consistent with progressive massive fibrosis (PMF), a micronodular pattern, and splenic microcalcifications [Figure 1A]. High-resolution CT revealed extensive fibrotic changes, traction bronchiectasis, and PMF in both upper lobes. Hilar and mediastinal lymph nodes exhibited “eggshell” calcifications. Micronodular infiltrates were observed in the upper lung zones. Abdominal sections of the same scan showed numerous, diffusely distributed calcified nodules (1–2 mm) within the spleen, along with calcified abdominal lymph nodes [Figure 1B–F]. Review of previous CT scans revealed that pulmonary and splenic findings had remained stable over the years. A positron emission tomography-CT conducted 3 years earlier showed mildly increased SUVmax, consistent with chronic inflammation, and splenic calcifications were already present. A follow-up abdominal ultrasound from one year prior showed a similar diffuse calcification pattern.

Figure 1.

PA chest radiograph and HRCT images show (a) bilateral pulmonary opacities and punctate splenic calcifications (red and black arrows), (b) consolidated areas in posterior upper lobes (yellow arrows), (c) diffuse micronodular infiltrates (light blue arrows), (d) multiple calcified splenic nodules (black arrow), (e) calcified mediastinal lymph nodes (yellow-orange arrows), and (f) multiple calcified splenic nodules on axial mediastinal HRCT (green arrow). HRCT = high-resolution computed tomography, PA = posteroanterior

Microbiological evaluation—including sputum culture, three serial acid-fast bacilli smears, and interferon-gamma release assay—was negative. Serologic testing for human immunodeficiency virus, histoplasmosis, brucellosis, and fungal infections was unremarkable. Arterial blood gas analysis showed pH 7.42, pCO₂ 42.6 mmHg, pO₂ 56.8 mmHg, and oxygen saturation 88%.

Supportive therapy was initiated with nasal oxygen, intravenous corticosteroids, empirical broad-spectrum antibiotics, and bronchodilators. Pulmonary function tests revealed a forced expiratory volume in 1 second (FEV₁) of 31% predicted, forced vital capacity (FVC) of 57% predicted, FEV₁/FVC ratio of 76%, and diffusion capacity of the lungs for carbon monoxide of 41% predicted.

Echocardiography demonstrated normal right and left heart chambers. Left ventricular hypertrophy was present, the ascending aorta was dilated (4.1 cm), ejection fraction was 55%, and systolic pulmonary artery pressure was 30 mmHg.

The case was reviewed by a multidisciplinary team including pulmonology, occupational medicine, radiology, and pathology specialists. Based on clinical presentation, detailed occupational history, laboratory and imaging findings, the diagnosis of complicated silicosis with extrapulmonary involvement—specifically splenic silicosis—was confirmed. The patient had previously received an occupational disease report and was granted permanent disability benefits.

Upon discharge, he was prescribed long-term oxygen therapy and long-acting bronchodilators. Annual influenza and pneumococcal vaccinations were recommended, and he was referred to a pulmonary rehabilitation program.

DISCUSSION

Silicosis is an irreversible fibrotic lung disease caused by prolonged inhalation of respirable crystalline silica, primarily in occupational settings. It remains the most common form of pneumoconiosis worldwide, accounting for approximately 90% of cases.[6] The disease is especially prevalent in high-risk industries such as mining, construction, sandblasting, and ceramic manufacturing.[2] Although its global prevalence has slightly declined—from 33.13 per 100,000 in 1990 to 31.60 in 2019—silicosis continues to represent a major public health issue, particularly in low- and middle-income countries.[7]

The pathogenesis of silica-induced lung injury involves a complex interplay of mechanisms. Inhaled silica particles are phagocytosed by pulmonary macrophages, but their cytotoxicity leads to cell damage and death. Additionally, silica stimulates the generation of reactive oxygen species, initiating inflammatory cascades and resulting in fibrosis. Lysosomal rupture activates NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasomes, promoting the release of proinflammatory cytokines such as interleukin (IL)-1β, IL-18, and IL-17. Furthermore, silica exposure provokes complex immune responses that contribute to chronic inflammation, extracellular matrix deposition, and formation of silicotic nodules.[8]

A literature review on splenic silicosis was conducted via PubMed and Google Scholar using keywords including “splenic,” “spleen,” “silicosis,” “splenic calcification,” “splenic involvement,” and “splenic nodules.” Approximately 12 case reports were identified [Table 1].[3,9,10,11,12,13,14,15,16,17,18,19] Although full texts were not accessible for all cases, those available revealed that patients with splenic involvement consistently exhibited pulmonary silicosis and hilar/mediastinal lymph node calcifications.[3,10,12,13,15] PMF was frequently noted.[3,11,12,13,15,18,19] A similar radiologic pattern was observed in our case, supporting the notion that splenic silicosis tends to occur in individuals with substantial silica exposure and advanced-stage pulmonary disease. When our case is considered in the context of existing literature, we suggest that extrapulmonary calcifications should not be dismissed as incidental or clinically irrelevant. Instead, they may serve as indicators of systemic silica burden. In contrast to our case, some reports also described calcified nodules in the liver.[9,11,12,14,15,16] In nearly all cases, including ours, the radiologic appearance of splenic silicosis was characterized by multiple small, well-defined, rounded calcified micronodules—morphologically similar to those found in lung parenchyma.

Table 1.

Summary of splenic silicosis case reports in the literature

N/reference (Author, Year)	Number of patients/sex	Age (years)	Occupation	Duration of exposure (years)	Clinical presentation	Splenic findings	Other organ involvement
Bai et al. (2021)[3]*	1/male	50	Borewell digger	>20	PMF, eggshell calcification	Irregular, coarse calcified lesion	No
Vanhoenacker et al. (2001)[9]*	1/male	62			Chronic silicosis	Small, distinct micronodules	Liver
Shen and Chen (2013)[10]*	1/female	58	Ceramic worker	14	Chronic silicosis, eggshell calcification	Small, distinct micronodules
Ufuk (2020)[11]	1/male	48	Dental technician		PMF, SLE	Small, distinct micronodules	Liver
Carreño Hernández et al. (2019)[12]	1/male	44	Sandblaster	5	PMF, eggshell calcification	Small, distinct micronodules	Bone marrow, liver
Yatera et al. (2015)[13]	1/male	61	Glass factory worker	22	PMF, eggshell calcification	Small, distinct micronodules and conglomeration	Retroperitoneal lymph node
Oswald et al. (1995)[14]*					Chronic silicosis	Small, distinct micronodules	Liver
Langlois et al. (1977)[15]*					PMF, eggshell calcification	Small, distinct micronodules	Liver
Ortuño and Sampedro (1974)[16]*							Liver
Doglioni et al. (1957)[17]*
Belt (1939)[18]*	1/male	50	Metal grinder	15	PMF, miliary tuberculosis	Small, distinct micronodules
Polachek and Pijanowski (1960)[19]*	1/male	61	Sandblaster	5	PMF, miliary tuberculosis	Small, distinct micronodules

*The full text of the article was not accessible. PMF=progressive massive fibrosis, SLE=systemic lupus erythematosus

The differential diagnosis of punctate splenic calcifications includes tuberculosis, acquired immunodeficiency syndromes, histoplasmosis, resolved Pneumocystis jirovecii infections, collagen vascular diseases, amyloidosis, and Gamna–Gandy bodies.[3,9] For patients with a history of occupational silica exposure and/or confirmed pulmonary silicosis, this entity should be actively considered.

Splenic involvement in silicosis is usually secondary and is often referred to as “metastatic.” Dissemination of silica particles occurs via hematogenous and lymphatic routes. Hematogenous spread typically follows embolic events after the rupture of a dust-laden hilar lymph node into a pulmonary vein. Lymphatic dissemination may proceed from pulmonary lymphatics to the thoracic duct and systemic circulation, via the pulmonary ligament to abdominal pre-aortic nodes, or through retrograde flow from posterior mediastinal to peripancreatic nodes and ultimately the spleen.[3,10]

Patient perspective

The patient presented with progressive exertional dyspnea, cough, and fatigue—symptoms he had experienced for years but which had worsened recently. He was already aware of his silicosis diagnosis and thus not surprised by his respiratory condition. However, he expressed surprise upon learning that silica exposure could cause calcified nodules in the spleen. Being retired, he no longer used personal protective equipment. He expressed satisfaction with the diagnostic process and the treatment plan provided.

CONCLUSION

Calcification of the hilar and mediastinal lymph nodes, particularly in an “eggshell” pattern, is commonly observed in silicosis. Although splenic calcification is not typical, it indicates high cumulative silica exposure and advanced disease, underscoring the need for vigilance in occupational health surveillance. Recognition of splenic silicosis has important diagnostic and prognostic implications. Calcifications in extrathoracic organs, such as the spleen, are rarely observed in patients with silicosis. This finding may reflect the systemic effects of silica exposure and should be carefully considered in the differential diagnosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published, and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.