Arthralgia, dry mouth and gritty eyes
Q: A 48-year-old woman presents with arthralgia, dry mouth and gritty eyes. Her rheumatoid factor (RF) is positive and antinuclear antibody (ANA) titre is 1:640, speckled pattern. What further tests might assist with diagnosis?
A: This case suggests primary Sjögren’s syndrome (SS), an autoimmune disorder characterised by lymphocytic infiltration and destruction of salivary and lacrimal glands. The positive RF and arthralgias can cause diagnostic confusion with rheumatoid arthritis.
Keratoconjunctivitis sicca can be confirmed by a Schirmer’s test of tear production or corneal rose-bengal staining.
A blood count may show mild lymphopenia and elevated ESR. Tests to confirm a systemic autoimmune disorder include serum immunoglobulins (increased IgG concentration); serum electrophoresis (polyclonal increase in immunoglobulins); and complements (low C4).
The most specific test for primary SS is extractable nuclear antigen (ENA), performed in conjunction with ANA, that detects autoantibodies against the Ro/SSA and La/SSB nuclear proteins. Patients with true autoimmune-mediated primary SS have either circulating anti-Ro/SSA alone or anti-Ro/SSA and anti-La/SSB as a linked set.
These autoantibodies are also seen in systemic lupus erythematosus (SLE), but rarely in RA with secondary SS. Patients with SLE can be distinguished serologically by the presence of anti-double stranded (ds) DNA antibodies.
The association of anti-Ro/La with symptoms of dry eyes, xerostomia, and a positive Schirmer’s test or rose-bengal staining has a sensitivity and specificity of 94% for primary SS.
The diagnosis can be confirmed in patients who lack anti-Ro/La (approximately 10% of cases) by a labial salivary gland biopsy. A lymphocyte focus score of ≥1 is considered positive for sialadenitis in SS.
A small number of patients with primary SS negative for Ro/La may have antibodies against the Ro52 protein which can be detected by new line blot assays.