Diaphragm strength in acute systemic lupus erythematosus in a patient withparadoxical abdominal motion and reduced lung volumes

Diaphragmatic weakness is reported as a common feature of the shrinking lun g syndrome of systemic lupus erythematosus (SLE). However, in chronic stabl e SLE it has been shown that, despite poor performance of voluntary tests o f diaphragm strength, twitch pressures obtained by stimulating the phrenic nerves are normal. We present a patient with acute SLE and pulmonary involv ement who, despite having paradoxical abdominal motion and low maximal insp iratory pressures during voluntary manoeuvres, had normal diaphragm strengt h when assessed with magnetic stimulation of the phrenic nerves. Following immunosuppressive therapy symptoms and lung function improved, yet diaphrag m contractility remained normal and unchanged. We suggest that this case su pports the view that reduced diaphragm muscle contractility per se does not explain the small volume lungs and respiratory symptoms in patients with a cute SLE.