AbstractAutoantibodies to the 75-kDa and 100-kDa subunits of the PM/Scl nucleolar protein complex are associated with an overlap syndrome, manifesting with clinical features of systemic sclerosis and idiopathic inflammatory myopathy. We describe the diverse clinical features in a series of 4 cases with anti-PM/Scl-75 and/or anti-PM/Scl-100 antibodies, including severe proximal muscle weakness, oesophageal dysfunction, respiratory weakness requiring mechanical ventilation, Raynaud’s, calcinosis cutis, sclerodactyly and critical digital ischaemia. Despite the severity of striated and oesophageal muscle weakness, all patients responded very well to immune suppression, and calcinosis cutis in one case regressed substantially. We highlight the efficacy of Rituximab and intravenous immunoglobulin therapy (IVIg) in these cases, enabling return to normal muscle function within six months. Rituximab was preferentially chosen for cases with hyper-gammaglobulinemia and multiple autoantibodies in addition to anti-PM/Scl, and IVIg was utilised for cases where a rapid onset of effect was required, such as severe ventilator-dependent respiratory muscle weakness and oesophageal dysfunction.