Computed Tomographic Imaging in Connective Tissue Diseases

Joseph Barnett, FRCR; Anand Devaraj, MD, MRCP, FRCR

Disclosures

Semin Respir Crit Care Med. 2019;40(2):159-172. 

In This Article

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory arthritis affecting ~1% of the population. It is often associated with systemic autoimmune disease, and pulmonary involvement is common. While the cause is unknown, a combination of genetic and environmental risk factors has been established. Fascinatingly, the lungs and oral mucosa have been implicated in the initial phases of disease.[1]

Within the lungs, RA can affect all compartments, namely, the airways, interstitium, pleura, and pulmonary vasculature.

Epidemiology

In recent times, national level cohort studies on patients with RA have provided valuable data on the epidemiology of pulmonary disease. The presence of interstitial lung disease (ILD) in patients with RA is around 5%.[2,3] The prevalence of bronchiectasis in RA independent of interstitial fibrosis (bronchiectasis rheumatoid overlap syndrome) is less certain, as population level imaging is not available and few studies distinguish freestanding from traction bronchiectasis. In small cohorts of patients examined retrospectively, the rate of freestanding bronchiectasis is reported at around 20%,[4,5] and it should, however, be noted that the rates of symptomatic bronchiectasis in patients with RA is far lower, at around 3%.[6]

While small amounts of pleural disease in RA are common on autopsy studies,[7] symptomatic pleurisy is less, and radiographic pleural effusion is uncommon, described in 6% of patients in one early study.[8]

HRCT Appearances

Airways Disease. Laryngeal involvement of RA may be visible on high-resolution computed tomographic (HRCT) scan, manifesting as erosion of periarticular cartilage, joint narrowing, or fusion of the cricothyroid and cricoarytenoid joints.[9,10]

On HRCT, freestanding bronchiectasis (as opposed to traction bronchiectasis secondary to fibrosis) tends to be of a cylindrical morphology,[5] localized as opposed to pan lobar,[5] predominates in the lower lobes,[4] and is often associated with bronchial wall thickening on HRCT.

Small airways disease corresponds to airways beneath the resolution of HRCT when not diseased,[11] and can be broadly classified into obliterative and exudative pathologies, both of which can be encountered in patients with RA.

On HRCT, obliterative bronchiolitis manifests as mosaic attenuation, with regions of relatively black lung containing constricted vessels[12] on inspiratory imaging, and air trapping on expiration. Ancillary findings include abnormalities of the proximal large airways, including freestanding bronchiectasis and airways thickening.[13] Mosaic attenuation represents the manifestation of pathological narrowing and obliteration of respiratory bronchioles by fibrosis and inflammation.

Two distinct clinical entities of obliterative bronchiolitis exist in patients with RA. Bronchiolitis obliterans is a rare complication of RA, characterized with a progressive and often fatal clinical course, with widespread obliterative bronchiolitis on CT. D-penicillamine has been associated with bronchiolitis obliterans, although the role of D-penicillamine as the sole etiological agent is uncertain, given the rarity of bronchiolitis obliterans in patients receiving the drug for Wilson's disease.[14]

While the clinical syndrome of bronchiolitis obliterans is rare in patients with RA, CT features of obliterative bronchiolitis are relatively common and are often subclinical.[15] Areas of decreased attenuation on HRCT are present in two-thirds of patients with newly diagnosed RA in one study, in 18% of cases of more than 20% extent.[15] Air trapping on expiratory CT has also been shown to be present in the majority of cases in patients with RA-ILD.[16] HRCT features of obliterative bronchiolitis also appear to be more extensive in patients demonstrating anticyclic citrullinated peptide antibody (ACCPA).[17]

Follicular bronchiolitis is an exudative small airways disease characterized pathologically by bronchiolar lymphoid hyperplasia. On HRCT, this is characterized by centrilobular or tree-in-bud nodularity, the majority of patients also demonstrate ground-glass opacity.[18]

Parenchymal Disease. RA is associated with fibrotic ILD, which in a minority of patients may be antecedent to the development of joint disease.[19] Risk factors for ILD in RA include male sex, older age, smoking history, presence of rheumatoid factor,[19] and ACCPA.[20]

The majority of patients with RA-ILD exhibit a usual interstitial pneumonia (UIP) morphology,[21] characterized on HRCT by basal predominant subpleural reticulation, with or without honeycombing (Figure 1). Using idiopathic pulmonary fibrosis (IPF) diagnostic criteria, many patients with RA and UIP pattern fibrosis indistinguishable from patients with IPF on HRCT alone.[22] However, several HRCT features can suggest RA-ILD as opposed to IPF in addition to a clinical history of RA. Honeycomb cysts located in the mid or upper lungs are an uncommon finding in IPF but are described in a proportion of patients with RA-ILD.[23] The presence of bronchocentric fibrosis in the context of a UIP morphology has also been described in a minority of patients with RA-ILD.[24] HRCT features of airways disease may also point the radiologist to a diagnosis of RA-ILD, with expiratory air trapping significantly more prevalent than in IPF.[16]

Figure 1.

HRCT in a 74-year-old female patient with RA and ILD. The CT appearances are of UIP, with peripheral honeycombing at the lung bases (top panel), and significant upper and mid-lung involvement (middle and top panels). A left upper lobe pulmonary nodules represent biopsy proven adenocarcinoma, a recognized complication in patients with RA-ILD. CT, computed tomography; HRCT, high-resolution computed tomography; ILD, interstitial lung disease; RA, rheumatoid arthritis; UIP, usual interstitial pneumonia.

Of patients with RA and non-UIP ILD, a nonspecific interstitial pneumonia (NSIP) or unclassifiable HRCT morphologies are the next most common phenotypes, being present in around 10 to 15% of patients.[21,25,26] Fibrotic organizing pneumonias (OPs), lymphocytic interstitial pneumonias, and desquamative interstitial pneumonias (DIPs) are rare.[25]

Rheumatoid pneumoconiosis (Caplan's syndrome) represents a characteristic HRCT morphology of fibrosis which occurs in the context of RA and occupational dust-related pneumoconiosis.[27] It is characterized by pulmonary nodules, which may have basal and peripheral distribution.[28] This nodularity can progress to progressive massive fibrosis, characterized on HRCT by perihilar consolidative fibrosis, causing volume loss.

The entity of diffuse alveolar damage (DAD) has long been recognized to be associated with RA,[29] where it can represent the first presentation of an RA-associated ILD[30] or, more frequently, as an acute exacerbation of a fibrotic ILD.[30] Rates of exacerbation among patients with UIP-RAILD may be similar to those in IPF,[31] and acute exacerbations may be encountered in non-UIP RAILD.[32] On HRCT, DAD/acute exacerbation is characterized by ground-glass infiltration, which may be diffuse, peripheral, or multifocal in distribution,[33] findings which are often indistinguishable from pulmonary infection.

Smoking rates in patients with RAILD vary between 38 and 75%,[20,26] and rates of emphysema coexisting with RAILD are correspondingly high, of up to 21% in some cohorts.[34] Fascinatingly, emphysema has been identified in patients with RAILD, but no smoking history seen in 27% of never smokers in one large study.[35] The rupture of emphysematous bullae or subpleural blebs may result in pneumothorax.

Patients with RA are predisposed to pulmonary nodules, both rheumatoid nodules per se and lung malignancy. Compared with malignancy, rheumatoid nodules are more likely to be multiplicious, have a smooth border, cavitate, contact the pleura, have a subpleural rind of soft tissue, and demonstrate satellite nodules.[36] Complications of rheumatoid nodules include pneumothorax,[37] bronchopleural fistula,[37] secondary infections,[38] and pleural effusion.

Pleural Disease. In addition to the above causes of pleural disease secondary to parenchymal disease, primary involvement of the pleura can also occur in RA with pleural inflammation manifesting on HRCT as pleural effusions or thickening. If chronic, pleural inflammation can mature into pleural fibrosis, which can cause restriction of the lung, a clinical entity described as "trapped lung." On HRCT, trapped lung appears as diffuse pleural thickening with ipsilateral reduction in lung volume.

Clinical Significance of CT in RA Lung Disease

A large United Kingdom-based prospective cohort of patients with early RA found pulmonary disease the second largest cause of mortality in patients with RA.[39] Patients with RA are at greater risk of death secondary to pulmonary fibrosis (defined radiologically) and infection than the age-matched population[39,40] and also relative to patients with RA without fibrosis.[3]

HRCT patterns of pulmonary fibrosis have been shown to correlate well with histopathological morphologies,[41] providing prognostic information and largely mitigating the need for surgical biopsy in patients with RA-ILD. In RA-ILD, a UIP disease morphology[42] and fibrosis extent have been shown to predict mortality.[20,23] Indeed, patients with a UIP pattern may have similar survival to patients with IPF.[23,24,42]

The observation, in one cohort study, that patients with RA-ILD had high risk of death within 30 days of diagnosis of RA-ILD may reflect acute exacerbations of pulmonary fibrosis as a particular risk factor.[43,44] Indeed, acute exacerbation has been shown to be an independent prognostic factor in patients with RA-ILD.[31] Rates of exacerbation among patients with RA-UIP may be similar to those in IPF.[31]

Severe bronchiectasis is a relative contraindication to tumor necrosis factor (TNF)-α inhibitor therapy for RA joint disease, and indeed, the presence of CT features of small and large airways disease has been shown to correlate with increased risk of infection in RA patients treated with long-term biological therapies.[45]

Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a protean autoimmune condition, which can affect any organ. The reported prevalence is 50 cases per 100,000 in the United States, being more common in women.[46] Clinical manifestations include constitutional symptoms, nonerosive arthritis, skin lesions, and vascular anomalies including Raynaud's phenomenon and thromboembolic disease. Within the chest, SLE can affect the pulmonary parenchyma, airways, pleura, chest wall, and heart. Despite this prevalence, few prospective studies have been performed with regard to thoracic disease. Pleurisy is likely to be the most common thoracic symptom, reported in around one-third of patients. ILD is rare, probably present in around 1% of patients.[47,48]

Pleural Disease. The presence of a pleural effusion in a patient with SLE can represent primary involvement of the pleura, or be secondary to the complications of other organ involvement, including pulmonary thromboembolism, infection, cardiac, or renal disease. In primary involvement, effusions are generally small, and following resolution can cause persistent pleural thickening.[49] SLE can also cause "shrinking lung syndrome," characterized by progressive lung volume loss without obvious parenchymal or pleural cause, which is often symptomatic. The pathogenesis of this condition is uncertain.

Parenchymal. Patients with SLE are at risk of parenchymal lung disease of several etiologies, many of which have similar clinical presentations (including dyspnea, fever, and cough) and similar radiological appearances.

Acute lupus pneumonitis is an uncommon manifestation of SLE, characterized clinically by an abrupt onset of respiratory distress and pathologically by an acute lung injury. The few data available specifically regarding the HRCT features of acute lupus pneumonitis suggest that it has similar appearances to acute interstitial pneumonia of any cause, of diffuse or patchy ground-glass opacity (Figure 2).[50] One small case series described 50% of cases of acute pneumonitis representing the first manifestation of SLE.[51] Incidences of acute lupus pneumonitis can be associated with flares of SLE in other organs.

Figure 2.

Patient with systemic lupus erythematosus and interstitial lung disease. The fibrosis is mid-lung predominant (middle panel) and has a ground-glass component. At the lung bases (top panel), there is honeycomb cyst formation, on the left demonstrating a bronchocentric distribution. The patient was subsequently admitted with acute respiratory distress (bottom panel), and the HRCT features are of a diffuse ground-glass infiltrate. The final clinical diagnosis was of acute lupus pneumonitis. HRCT, high-resolution computed tomography.

Pulmonary hemorrhage is a rare complication of SLE, which manifests clinically as respiratory distress, fever, and hemoptysis, although the latter may be lacking.[52] Similar to acute lupus pneumonia, flares of SLE in other organs have been associated with pulmonary alveolar hemorrhage.[52] On HRCT, while the imaging features of pulmonary hemorrhage can be broadly said to constitute ground-glass opacity, the presence of 1 to 3 mm centrilobular ground-glass nodules, of uniform size, is a feature more specific to pulmonary hemorrhage.[53] In the subacute phase of pulmonary hemorrhage, smooth interlobular septal thickening is sometimes present.[53] Pulmonary effusions are rarely seen in pulmonary hemorrhage, in some cases permitting radiological differentiation of this condition from pulmonary edema, to which patients with SLE are also susceptible.

Patients with SLE are also at risk of opportunistic infection, which may be due to immunological dysregulation innate to the disease or alternatively secondary to immunosuppressive therapy. The radiological appearances are, in many cases, nonspecific and show overlap with other SLE-related parenchymal diseases.

Interstitial Lung Disease. Data regarding the CT appearances of ILD in SLE are sparse, with many of the few dedicated studies[54–56] performed before the classification of NSIP as a distinct entity.[57] Retrospective interpretation of these studies, along with a recent series in 10 patients,[25] suggests an NSIP pattern to be the most prevalent morphology of fibrosis, although UIP,[58] OP,[59] lymphoid interstitial pneumonia (LIP),[60] and DIP[61] have all been described in small cohorts. Male sex,[47] older age at disease onset,[62] advancing age,[47] and history of acute lupus pneumonitis[51] have all been cited as risk factors for the development of SLE-ILD.

Airways Disease. Bronchiectasis has been described in CT studies on SLE, being present in 12% in one retrospective review of patients with SLE undergoing HRCT.[63]

Vascular Disease. PH is uncommon in SLE, being reported in around 5%[48,64] of patients. PH can be caused by chronic thromboembolic disease, and indeed, in one prospective, cross-sectional cohort study, the presence of lupus anticoagulant was significantly associated with PH.[65] Pulmonary arterial hypertension (PAH) is also well described in patients with SLE, in some cases, this may be secondary to immune-mediated vasculopathy.[66]

Clinical Significance. Patients with SLE have around a threefold increase in all-cause mortality relative to the general population.[67] Renal disease and infection have been shown to be the conditions with the highest mortality associated with SLE,[67] the presence of PH defined on echocardiography has also shown to independently predict mortality.[48,68]

Historical case studies describe very high rates of mortality associated with acute lupus[51] and pulmonary hemorrhage,[69] more recent case series demonstrate much lower mortality,[52] perhaps representing improvements in therapy or more representative patient cohorts.

The significance of ILD detected on HRCT in SLE is uncertain, although confident analysis is hampered by a lack of data. In the data that exist, no consistent relationship between HRCT findings of ILD and pulmonary function test (PFT) indices,[54] survival or symptoms[63] has been demonstrated.

The radiological diagnosis of shrinking lung syndrome is important, as while the optimal therapy for this condition has yet to be defined, several treatment regimens have been associated with improvement in symptoms and pulmonary function.[70]

Systemic Sclerosis

Systemic sclerosis (SSc) represents the combination of scleroderma with internal organ involvement and is broadly categorized into limited cutaneous SSc and diffuse cutaneous SSc, on the basis of whether dermatological abnormalities are limited to the distal extremities or are present more diffusely. A minority of patients with SSc have no cutaneous symptoms. Estimates of prevalence are hampered by a lack of data but are thought to be in the order of 28 per 100,000 population.[71] Pulmonary involvement, including ILDs and pulmonary fibrosis, is seen in the majority of patients with SSc.[72]

Parenchymal Disease. While patients with diffuse SSc have the greatest likelihood of developing an ILD, a proportion of patients with the limited cutaneous form of the disease may also develop ILD.[73]

The most frequent radiological morphology of fibrosis in SSc is NSIP,[74] broadly characterized on HRCT as ground-glass opacity admixed with fine reticulation,[74] containing traction bronchiectasis.

Several radiological signs are important when attempting to distinguish NSIP from an UIP morphology of fibrosis (Figure 3), as both manifest as peripheral, basal predominant reticulation with traction bronchiectasis.

Figure 3.

HRCT features of NSIP in three different patients with SSc-associated interstitial lung disease. Panel 1, axial image of NSIP, a ground-glass infiltrate containing fine reticulation causing traction bronchiectasis. A slim rind of subpleural lung is spared. Note the dilated esophagus. Panel 2, the straight edge sign; the upper limit of fibrosis on coronal imaging is remarkably straight, making a right angle with the pleural surface. Panel 3, bronchocentric disease this is postulated to be associated with aspiration in patients with SSc-ILD. HRCT, high-resolution computed tomography; ILD, interstitial lung disease; NSIP, nonspecific interstitial pneumonia; SSc, systemic sclerosis.

Distinction should be made whether ground-glass opacity is caused by fibrosis (namely, associated with traction bronchiectasis or volume loss) or whether the ground-glass opacity is "freestanding," suggestive of a potentially reversible inflammatory infiltrate[75] not specific to NSIP. This distinction, however, is not always clear, as patients with ground-glass opacity without overt traction bronchiectasis may still demonstrate elements of fibrosis histopathologically.

In patients with UIP-IPF, fibrotic ground-glass opacity is not uncommonly encountered, but tends to be associated with coarser reticulation than in NSIP,[74] and is rarely seen to predominate over the extent of reticulation.[22]

On axial distribution, sparing of the immediate subpleural lung is a finding in NSIP, but one not commonly seen in IPF or fibrotic hypersensitivity pneumonitis,[76] and therefore, can be considered supportive of a diagnosis of NSIP in combination with other features.

The presence of traction bronchioloectasis,[77] as opposed to traction bronchiectasis, may differentiate NSIP from UIP-IPF, although the utility of this finding has not been consistently shown.[76]

The craniocaudal distribution of fibrosis may also be useful in the radiological differentiation of NSIP from UIP. NSIP tends to spare the upper lobes relative to IPF, even after accounting for disease extent.[78] On coronal imaging, the presence of a sharply defined upper margin of fibrosis with a straight edge is very specific, and moderately sensitive for NSIP as opposed to UIP on histology.[79]

The "four corners sign," comprising "distribution focally or disproportionately involving the posterosuperior lower lobes and anterolateral mid-upper lobes"[80] is infrequently present in SSc-ILD, but is very specific for this diagnosis, as opposed to IPF. It must be noted, however, that this sign is demonstrated in few patients with CT-UIP morphology,[80] potentially limiting its utility.

While etiology of an NSIP pattern is primarily a clinical question, the presence of esophageal dilatation and lymph node enlargement are more frequent findings in SSc-ILD than in other CTDs associated with ILD.[25]

On HRCT, bronchocentric disease, including ground-glass opacities and consolidation can also be seen, which has been postulated to represent aspiration, particularly in the context of esophageal dilatation.[81]

Vascular Disease. PH occurs in both forms of SSc, four classes of PH are well recognized: PAH, chronic thromboembolic disease, secondary to ILD, and secondary to left ventricular dysfunction.

Manifestations of PH in SSc include the general HRCT features of PH, pericardial effusion and thickening,[82] and increased pulmonary artery diameter.[83] Indeed, in the context of an ILD, pericardial thickening may suggest SSc even in the absence of cutaneous disease.[84]

Additionally, pulmonary ground-glass opacities are well described. In many patients with severe disease, a mosaic attenuation is present, distinguished from the findings of obliterative small airways disease by the lack of air trapping on expiratory CT.[85] In the context of PH, areas of decreased attenuation containing constricted vessels represent the sequelae of decreased perfusion, whereas increased density represents vascular hyperemia.

A second morphology of ground-glass opacity is also described in PH, that is, centrilobular ground-glass nodules. A central distribution of such ground-glass opacities have been shown to be more frequently present in SSc-PH than in other causes of PH.[86]

Clinical Significance. Respiratory disease is a principle cause of mortality in patients with SSc,[87] and HRCT plays a central role in both its identification and prognostication, outperforming PFTs and plain radiograph as a screening tool.[88]

Treatment with immunosuppressive therapy has been shown to be of benefit in patients with SSc-related pulmonary disease,[89] indeed, a small cohort of patients can experience regression of disease on HRCT following treatment.[75] However, judicious application of potent immunosuppressive therapies is necessary, due to the risks of iatrogenic infection, myelosuppression, and infertility. Conversely, patients with limited extent disease on HRCT, and no evidence of PH on echocardiography, may be more amenable to a "watchful waiting" treatment strategy.[90]

A widely used[91] algorithm to predict risk of death related to ILD in SSc, and to therefore guide treatment, is based on disease extent, with limited disease defined as a fibrosis extent of <10% and extensive disease >30% fibrosis. In intermediate cases, a forced vital capacity measurement (with threshold of 70%) is used to stratify patients.[92]

Identification of radiological disease morphology in SSc-ILD may also have utility, a UIP morphology has been shown to predict disease progression on HRCT. The presence of emphysema,[93] UIP disease morphology,[94] and pleuropulmonary fibroelastosis[95] on HRCT have also been linked to decreased survival in SSc-ILD. Furthermore, the recognition of emphysema on HRCT is important in interpretation of PFTs which can be confounded by emphysema,[96] which has important implications for screening and monitoring of patients.

Detection of an enlarged pulmonary artery on HRCT is able to predict PH on right heart catheter, and transplant free survival[97] in patients with SSc, and therefore, should actively be sought on HRCT.

Sjogren's Syndrome

Sjogren's syndrome (SS) is a chronic autoimmune condition which affects the lacrimal and salivary gland function, resulting in dryness of the mouth and eyes. As a primary syndrome, it can be associated with a variety of extraglandular systemic manifestations, including within the lungs. The prevalence is estimated at 43 per 100,000.[98] Results from one cross-sectional study suggest that while 20% of patients report chronic respiratory symptoms,[99] the prevalence of small airways disease is around 5%, with ILD less common still.[99]

Airways Disease

Involvement of the airways can be secondary to glandular disease in the upper aerodigestive tract or represent extraglandular disease.

Freestanding bronchiectasis in SS tends to be cylindrical and predominates in the lower lobes.[100] The characteristic small airways disease in SS is follicular bronchiolitis, although CT features of obstructive small airways disease have also been described.[101] The CT appearances of follicular bronchiolitis are identical to those described in patients with RA (as described earlier). Follicular bronchiolitis may occur in isolation, or in combination with NSIP or OP. Presentation with severe bronchiolitis, causing respiratory failure, has also been described in SS.[102]

Parenchymal Disease

A nonspecific interstitial pneumonitis is the most common ILD in SS,[25,103,104] which can overlap with OP (see "Polymyositis/Dermatomyositis" section).[104] A UIP morphology is not uncommon.[104]

Lymphocytic interstitial pneumonia is also well described in patients with SS (Figure 4) and is occasionally also encountered in other CTDs.[25] On HRCT, it is characterized by ground-glass opacity (which may be diffuse, patchy, or peripheral), poorly defined centrilobular nodules[105] and thin-walled cysts which demonstrate a random distribution.[106] Thin-walled cysts may represent the only feature in many patients. Peribronchovascular or interlobular septal thickening were additional CT findings present in a majority of patients in one case series.[105] While LIP is a disease on the lymphoproliferative spectrum, it is thought not to progress directly to pulmonary lymphoma, early case reports demonstrating such a progression most likely had incorrectly classified progenitor lesions as LIP.[107]

Figure 4.

A patient with Sjogren's syndrome and an interstitial lung disease. The combination of ground-glass opacity, solid pulmonary nodules, and thin-walled cysts is in keeping with lymphocytic interstitial pneumonia. A solid left lower lobe nodule is undergoing cavitation (bottom panel).

Pulmonary lymphoma is associated with SS in its own right, most frequently of the marginal zone lymphoma subtype, which arises in the mucosa of the pulmonary airways. This extranodal location gives rise to parenchymal lesions on HRCT (as opposed to nodal disease, characteristic of secondary pulmonary lymphoma), which may be nodular or consolidative in nature. In both forms, air bronchograms are encountered, which may be dilated.[108]

Nodular lymphoid hyperplasia, formerly referred to as "pseudolymphoma" is a benign lymphoproliferative parenchymal lesion which presents most commonly as a solitary nodule or mass, but can mimic the HRCT appearances of pulmonary lymphoma. Differentiation of these two entities requires tissue diagnosis.

Nodular amyloidosis is a rare pathology associated with SS, presenting as pulmonary nodules, often multiple, which may or may not be calcified. Such amyloid nodules are often associated with thin-walled cysts.[109] In SS, amyloid deposition may be limited to the lungs, as opposed to representing systemic amyloid disease.

Pulmonary Hypertension

PH is associated with SS, although its prevalence is uncertain, a small echocardiographic screening study reported rates of around 25%.[110] A significant minority of patients with idiopathic PAH may subsequently develops SS.[111]

Clinical Significance

In patients with SS, respiratory symptoms are common, and the utility of HRCT is in detecting pulmonary disease. A significant cause of morbidity is xerotrachea characterized by chronic cough which has no radiological or functional correlate.[99] Conversely, airways disease and parenchymal or pulmonary vascular disease are readily detected by HRCT, and may warrant specific treatment. Patients with CT defined bronchiectasis and SS, as with other conditions, are at increased risk of respiratory infections and pneumonia.[100] The link between ILD subtype and prognosis in SS has not been established, although treatment regimens and objectives may be tailored to different morphologies.

HRCT can also be used to distinguish SS from other causes of sicca symptoms, in particular sarcoidosis, which shares both pathogenic and immunogenic features with Sjogren's syndrome.

HRCT plays a cardinal role in detecting lymphoma, at which SS patients are at a 16-fold increase relative to the general population.[112] While HRCT is well placed to identify pulmonary masses and nodules, tissue is often required to distinguish the various causes of consolidation and nodules in SS, as well as subtype of lymphoproliferative disorders.

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