Craigavon Area Hospital, Lurgan Road, Portadown BT63 5QQ, UK
SIR, Sjögren's syndrome (SS) is the second commonest autoimmune disease and is characterized by keratoconjunctivitis sicca and xerostomia. Some patients with SS also suffer from extraglandular disorders, including lung disease. The overall involvement of the respiratory system is more common in secondary SS (sSS) than in primary SS (pSS), but patients with pSS are more prone to interstitial lung disease, although it tends to be more severe in sSS [1, 2].
We evaluated retrospectively the medical notes of 10 patients with a diagnosis of probable or possible pSS using Fox's criteria, for evidence of pulmonary involvement. Nine patients were female and the mean age was 61 yr. Only four patients complained of symptoms directly related to the respiratory system. Eight patients had a full pulmonary function assessment performed, and all assessments were abnormal. Two patients had only spirometry performed, but as the technique was poor these results were not included. Five had evidence of a restrictive defect only [mean FEV1/FVC (forced expiratory volume in 1 s/forced vital capacity) 103% of predicted value], four of these patients having a significantly reduced transfer coefficient (mean KCO=56). The five patients with the restrictive defect underwent high-resolution CT scanning of the chest. This showed varying changes typical of the condition, all five having interstitial fibrosis, one having extensive lymphadenopathy and two having concomitant bronchiectasis.
The exact frequency of respiratory disease in pSS is not known. One report cites a frequency of 75% [2]. Our findings support this, eight out of 10 patients who underwent full pulmonary function testing having abnormal results despite the majority being asymptomatic. The CT scanning was useful in the diagnosis and differentiation of the pulmonary subtypes, and previous reports have shown interstitial changes on CT scanning despite normal chest X-rays [3]. A common histological pattern in patients with pSS is diffuse lymphocytic interstitial pneumonitis (LIP). LIP may progress to pseudolymphoma, a non-malignant extraglandular lesion, but this may progress to frank malignancy [4].
We recommend that all patients with SS should have full pulmonary physiology assessment even if asymptomatic from their respiratory system, and high-resolution CT scanning if the KCO is reduced, with regular reassessment of pulmonary involvement. One study suggests, however, that pulmonary involvement occurs early and that most patients do not develop progressive lung disease [5].
Notes
Correspondence to: S. A. Wright, Rheumatology Department, Musgrave Park Hospital, Stockman's Lane, Belfast BT9 7JB, UK. E-mail: stephen{at}wright866.fsnet.co.uk
References
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