Splenic silicosis, a rare extrapulmonary manifestation of occupational silica exposure: A case report

Silicosis remains among the oldest recognised occupational lung diseases, resulting from crystalline silica inhalation during industrial activities including mining, quarrying, sandblasting, and construction work [ 1 ]. The established pathophysiology involves alveolar macrophage activation by inhaled silica crystals, triggering inflammatory cascades that progress to pulmonary fibrosis and respiratory impairment [ 2 , 3 ]. However, silica particles can disseminate systemically via lymphohematogenous routes, affecting extrapulmonary organs rich in reticuloendothelial cells, potentially causing extrapulmonary silicosis [ 4 – 6 ]. Although extrapulmonary involvement has been recognised, it remains rare and probably underreported in the literature [ 5 , 7 ]. Splenic silicosis represents a particularly rare extrapulmonary manifestation, with documented cases remaining uncommon despite the spleen’s theoretical susceptibility as a major reticuloendothelial component [ 8 , 9 ]. When present, splenic involvement typically manifests as splenomegaly, calcified nodules, or progressive fibrosis detected during imaging studies [ 5 , 8 – 11 ]. Characteristic radiological findings include multiple micronodular calcifications, with some reports describing a subcapsular sparing pattern [ 12 ]. Each documented case of splenic silicosis contributes essential insights into systemic silica-related disease manifestations and establishes recognition patterns for clinical practice [ 13 ]. Herein, we report a case of complicated silicosis with splenic involvement in a sand sifting machine operator. Although traditional high-risk occupations such as sandblasting are well established, sand processing work has received limited attention in the literature. This case raises awareness of potential silica exposure risks in sand sifting operations and underscores the importance of timely health surveillance and comprehensive prevention strategies for workers in this industry.

A 46-year-old female with a history of occupational silica exposure presented for evaluation. She had worked as a sand sifting machine operator at a sand classification and packing factory from 1999 to 2005, totalling six years of exposure. The sand processed at the facility was used for industrial and construction purposes. Her duties involved sitting next to the sand sifting machine and manually clearing residual sand from the grill. She reported visible dust clouds during sifting operations. The working environment lacked adequate dust control measures: only one local exhaust ventilation unit was installed per machine, positioned far from the operator’s breathing zone, rendering it largely ineffective. There were no partitions between workstations on the open-plan factory floor, and dust spread extensively across her body and the surrounding work area. She worked without proper personal protective equipment, using only a piece of loincloth as an improvised mask, for eight to twelve hours daily, six days per week. To her knowledge, no industrial hygiene assessment or occupational surveillance was conducted at the workplace during her period of employment. In 2005, the patient developed a chronic dry cough and fatigue, symptoms that had persisted for approximately one year. No splenic or lymph node abnormalities were noted at that time. Chest radiography revealed diffuse nodular opacities in both lungs. Despite negative sputum smear microscopy, she was empirically treated for pulmonary tuberculosis with antituberculous drugs for nine months. Specifically, the patient was treated with 2 months of isoniazid, rifampicin, and ethambutol, followed by 7 months of isoniazid and rifampicin. Concerned that seven co-workers performing identical tasks had developed severe lung diseases, she decided to transition to non-silica-related employment. Importantly, based on available medical records, one developed complicated silicosis with recurrent pneumothorax requiring talc pleurodesis, while the others had chronic simple silicosis. Her symptoms gradually stabilised over the following three years, after which she was lost to follow-up. In October 2024, approximately 19 years after initial presentation, the patient presented to a hospital with upper respiratory tract symptoms and disclosed her history of previous lung disease. Apart from a known history of adenomyosis, she denied any history of autoimmune disease, other infections during the intervening period, or smoking. Her only persistent symptom attributable to her underlying lung condition was an occasional dry cough. She denied abdominal discomfort, pain, or distension, as well as constitutional symptoms such as fever and unintentional weight loss. Physical examination was unremarkable overall, with oxygen saturation of 99% on room air. However, abdominal examination revealed mild splenomegaly without associated tenderness, with the spleen palpated 2 cm below the left costal margin. There was no cervical lymphadenopathy on examination. Chest radiography demonstrated multiple calcified and non-calcified nodular opacities scattered throughout both lungs, with additional calcified opacities noted in the spleen ( Figure 1 ). According to the 2022 International Labour Organization Classification of Radiographs of Pneumoconioses, the chest radiograph was classified as silicosis q/q, 3/3, with category B large opacities [ 14 ]. Calcification was present in small pneumoconiotic opacities, accompanied by eggshell calcification of lymph nodes in bilateral paratracheal areas. The radiographic interpretation was confirmed by two National Institute for Occupational Safety and Health (NIOSH)-certified B readers. Computed tomography (CT) of the chest and abdomen was subsequently performed to further characterise these findings. Axial CT images of the chest demonstrated multiple calcified and non-calcified solid pulmonary nodules with centrilobular and perilymphatic distribution in both lungs ( Figure 2 ). Multiple calcified lymph nodes with eggshell appearances were observed in the mediastinum, bilateral internal mammary chains, and superior diaphragmatic regions. Bilateral conglomerate masses with internal calcification involving the superior segments of both lower lobes were identified, consistent with progressive massive fibrosis ( Figure 3 ). Axial CT images of the abdomen demonstrated multiple subcentimetre calcified nodules diffusely distributed throughout the splenic parenchyma, with calcified splenic hilar, hepatoduodenal, and retroperitoneal lymph nodes ( Figure 4 ). Posteroanterior upright chest radiograph demonstrating silicosis with extrapulmonary involvement. Diffuse calcified nodules are present in the spleen (asterisk), indicating systemic silica deposition. Diffuse bilateral calcified and non-calcified pulmonary nodules with conglomerate masses in the middle and lower lung fields (arrows), together with eggshell calcification of bilateral paratracheal lymph nodes (arrowheads), are demonstrated. Spirometry showed a forced expiratory volume in 1 second (FEV 1 ) of 51.0% predicted, forced vital capacity (FVC) of 60.0% predicted, and an FEV 1 /FVC ratio of 70.7%, suggestive of a restrictive ventilatory pattern. The diffusing capacity of the lung for carbon monoxide (DL CO ), the 6-minute walk test, and arterial blood gas analysis were not performed. Complete blood count showed microcytic anaemia (Hb 9.1 g/dL, Hct 30%, MCV 70.5 fL), consistent with known iron deficiency anaemia secondary to adenomyosis. The platelet count (149 × 10 9 /L) and white cell count (4.55 × 10 9 /L, with a normal differential) were unremarkable. Based on the characteristic radiological findings, occupational exposure history, and clinical presentation, the diagnosis of complicated silicosis with extrapulmonary splenic involvement was established. No disease-modifying treatment was initiated; management consisted of supportive measures, including patient education, appropriate vaccinations, avoidance of further silica exposure, and ongoing monitoring. Axial CT of the chest demonstrating diffuse pulmonary nodules and mediastinal lymphadenopathy. Lung window settings reveal multiple calcified pulmonary nodules distributed throughout both lungs. Eggshell calcification of mediastinal lymph nodes is present in the paratracheal, para-aortic, and internal mammary regions (arrows), a characteristic finding of silicosis. Abbreviations: CT, computed tomography. Axial CT of the chest demonstrating complicated silicosis. Lung window settings show bilateral conglomerate masses with internal calcification involving the superior segments of both lower lobes (arrows), consistent with progressive massive fibrosis secondary to silicosis. Abbreviations: CT, computed tomography. Axial CT of the abdomen demonstrating splenic and lymph node involvement. Soft tissue window settings reveal multiple calcified micronodules diffusely distributed throughout the splenic parenchyma with subcapsular sparing (asterisk). Calcified splenic hilar, hepatoduodenal, and retroperitoneal lymph nodes with eggshell appearances are also evident (arrows), indicating extrapulmonary silica deposition. Abbreviations: CT, computed tomography.

This case demonstrates splenic involvement in silicosis, a rare extrapulmonary manifestation of occupational silica exposure. The characteristic imaging pattern of multiple micronodular calcifications with subcapsular sparing observed in our patient aligns with previously reported cases [ 8 , 12 ]. This adds several novelties to the literature. First, the occupational setting of sand sifting/screening has probably received less attention than sandblasting. Second, the cluster of affected workers highlights an occupational hazard that might be overlooked. Finally, the radiological findings demonstrate worsening fibrotic and lymphadenopathic changes years after exposure had ceased. The morphological features of extrapulmonary silicotic lesions suggest that silica particles reach the spleen via lymphohaematogenous dissemination [ 4 , 5 ]. Splenic lesions range from loose histiocytic aggregates to characteristic sclerohyaline nodules, although the latter occur less frequently than in pulmonary involvement. Silicosis with splenic involvement is believed to be secondary to haematogenous, retrograde lymphatic spread, or a combination thereof, representing possible pathophysiological mechanisms [ 7 , 9 , 11 ]. The differential diagnosis of punctate splenic calcifications is extensive and includes tuberculosis, histoplasmosis, healed Pneumocystis carinii infection, acquired immunodeficiency syndrome, collagen vascular diseases, amyloidosis, and Gamna–Gandy bodies [ 8 , 11 , 13 ]. Silicosis and systemic lupus erythematosus should also be considered in patients presenting with calcified splenic lesions [ 12 ]. In this case, prior tuberculosis was the main differential diagnosis to consider, as she had received empirical antituberculous therapy in 2005. However, the diagnosis of tuberculosis was never confirmed microbiologically, and the imaging findings could be better explained as silicosis. Splenic involvement in tuberculosis is rare and typically occurs in disseminated disease and/or in people living with human immunodeficiency virus [ 15 , 16 ]. It is usually accompanied by fever or abdominal pain, neither of which was reported in this patient. For these reasons, together with an occupational history and characteristic radiological findings, microbiological re-assessment was not pursued in 2024. In addition, tissue confirmation was not performed, given the patient’s stable clinical course and the invasiveness of biopsy, which would not have altered management. Case reports describing silicosis with hepatosplenic calcifications remain scarce in the literature. Typically, splenic involvement shows an imaging pattern of numerous punctate calcified micronodules distributed throughout the spleen, sometimes with relative subcapsular sparing [ 12 ]. However, one case report depicted an irregular, coarsely calcified lesion in the mid-pole of the spleen in a patient with complicated silicosis [ 11 ]. Most documented cases involve abdominal calcifications in the peripancreatic lymph nodes, including the splenic hilar lymph nodes and along the splenic artery, often with a notable eggshell appearance [ 8 – 10 ]. Radiographically detectable calcified miliary silicotic nodules within the liver and spleen are even less frequently reported. Accelerated silicosis with bone marrow, hepatic, and splenic involvement has also been documented, demonstrating the systemic nature of severe silica-related disease [ 5 ]. The proposed pathophysiology involves retrograde lymphatic spread of silica particles or silica-laden macrophages from the chest to the abdomen. This probably results from lymphatic obstruction caused by progressive fibrosis of intrathoracic lymphatic channels and lymph nodes [ 8 ]. This mechanism may partly explain the association between splenic involvement, progressive massive fibrosis, and eggshell calcifications of intrathoracic lymph nodes. Table 1 summarises the characteristics of splenic silicosis cases reported in the literature. The present case initially presented in 2005 with diffuse nodular opacities consistent with simple silicosis. Over the subsequent 19 years, documented at two distinct time points ( Figure 5 ), the disease progressed to complicated silicosis with the development of progressive massive fibrosis, as demonstrated on recent imaging. The disease classification for this patient is somewhat unusual. Conventionally, chronic silicosis develops after 10–30 years of low-concentration silica exposure and progresses slowly, whereas the hallmark of accelerated silicosis is rapid disease progression, typically within less than 10 years from initial exposure [ 17 ]. The patient developed radiographic abnormalities after approximately six years of exposure, which therefore does not fit entirely into either disease type. However, the indolent clinical course and slow radiographic progression from simple to complicated silicosis may favour a chronic rather than accelerated form. A similar observation has been documented previously: one case report described chronic silicosis in a mining worker following only five months of high-intensity silica exposure [ 18 ]. This supports the notion that intensive exposure may result in earlier disease onset while maintaining the characteristic clinical and radiographic features of chronic silicosis. Demographic characteristics, occupational exposure, clinical features, and imaging findings in previously reported cases of silicosis with splenic involvement. All reported cases demonstrated pulmonary silicosis with concurrent splenic involvement. Subcapsular sparing of splenic calcifications, observed in the present case and one other report, is a characteristic radiological finding attributed to splenic blood flow patterns. Abbreviations: F, female; LN, lymph node; M, male; PMF, progressive massive fibrosis; y, years. Clinical timeline of the present case. A longitudinal study of Japanese tunnel workers demonstrated that silicosis can progress from simple to complicated stages even after cessation of silica exposure [ 19 ]. This finding aligns with the clinical course of this patient, in whom disease progression from simple to complicated silicosis occurred despite no further silica exposure. Furthermore, seven of her co-workers performing identical tasks at the same facility also developed silicosis, with one similarly progressing to complicated silicosis. This cluster of cases further supports the likelihood of high-intensity silica exposure in this workplace. To date, no high-risk host phenotype has been clearly established. Although polymorphisms in inflammatory cytokine genes have been investigated, the evidence regarding silicosis susceptibility or severity remains inconclusive [ 20 ]. Similarly, the role of smoking in silicosis is still controversial; however, it may contribute to deterioration in lung function [ 21 ]. In this regard, the present patient had no silicosis-relevant comorbidities and never smoked, consistent with the view that intense exposure alone may lead to disease in otherwise healthy individuals. Of her seven affected co-workers, only two had minor unrelated comorbidities, including peptic ulcer disease in one and hypertension in another. Sand screening and processing are recognised as high-intensity job categories for respirable crystalline silica exposure [ 22 – 24 ]. Even in regulated North American facilities equipped with engineering controls, workers performing sand screening and bagging have historically experienced respirable crystalline silica concentrations that frequently exceeded NIOSH-recommended exposure limits [ 24 ]. At the present facility, which lacked effective ventilation, workstation partitioning, and adequate respiratory protection, exposure was likely substantially higher. As retrospective quantitative measurement was not feasible, exposure was characterised semi-quantitatively using a job-exposure matrix framework: a high-intensity task performed 8–12 hours daily, six days per week, over six years of continuous employment, consistent with high cumulative respirable crystalline silica exposure. Currently, there is no effective treatment for silicosis, and disease progression continues even after exposure ceases [ 19 ]. Previously studied interventions, including corticosteroids and inhaled aluminium, have proven ineffective [ 1 ]. Given shared fibrotic pathways across interstitial lung diseases, antifibrotic agents are now being investigated, with trials of nintedanib in progressive pneumoconioses underway in Australia ( ClinicalTrials.gov NCT04161014 ) and the US [ 17 ]. Management thus remains supportive, including cessation of exposure, vaccination against infectious respiratory diseases, treatment of complications (e.g., concomitant infectious or autoimmune diseases), pulmonary rehabilitation, and lung transplantation in end-stage disease [ 25 ]. Equally important is ensuring appropriate compensation for affected workers. A limitation of this case report is that quantitative dust measurements and particle size analysis were not performed at the time of exposure, precluding precise characterisation of the exposure intensity. Additionally, the absence of histopathological confirmation represents a limitation; however, the characteristic radiological findings and occupational history are sufficient to establish the diagnosis of silicosis. In Thailand, the diagnosis of silicosis is established when at least two of three criteria are met: (i) silica exposure of at least two years; (ii) chest radiograph profusion 1/0 or greater according to the 2011 International Labour Organization Classification/International Classification of Radiographs of Pneumoconioses; and (iii) pathological or epidemiological evidence [ 26 ]. Even without biopsy, this case met all three criteria.

In conclusion, this case highlights splenic silicosis as a rare but recognisable extrapulmonary manifestation of occupational silica exposure. The diagnosis was established based on characteristic radiological findings and a detailed occupational history, without the need for invasive procedures. Importantly, intense silica exposure can lead to disease progression even in patients without comorbidities. Sand sifting operations represent an underrecognised source of silica exposure, and the occurrence of multiple cases at the same facility underscores the importance of comprehensive prevention strategies and early health surveillance for workers in sand processing industries.