A 33-year-old woman presented with an 8-month history of dry cough and progressive dyspnoea. Two months later, she developed dry eyes and mouth, petechial rash over both feet, left jaw pain and weight loss. She had no significant medical, medication, smoking or occupational history. Her father had Raynaud’s disease and paternal uncle had systemic lupus erythematosus.

Her physical examination revealed oxygen saturations of 94%, mild painful swelling of the left parotid gland and a petechial rash over the feet. Respiratory examination revealed bilateral inspiratory crackles and squawks up to mid-zones.

Routine blood investigations revealed normal full blood count, routine biochemistry and a raised plasma viscosity 2.43 mPa.s (1.50–1.72). Total serum protein was raised at 98 (60–80) g/L with a polyclonal response with elevated immunoglobulin IgG 59 g/L (6–16) and IgM 4.54 g/L (0.5–1.9) levels. There were no serum or urine monoclonal proteins. Autoantibody examination was positive for antinuclear antibody, subtyped as anti-Ro (SS-A) and anti-La (SS-B) antibodies. Rheumatoid factor was negative. Serum …