An 11-year-old male patient suffering mixed connective tissue disease with life-threatening pulmonary arterial hypertension, progressive heart failure (New York Heart Association class III-IV), skin ulcers, Raynaud's phenomenon and arthritis, showing no improvement after intensive immunosuppressive therapy or high dose steroids, was treated with immunoadsorption onto protein A. With a combined therapy of low-dose cortisone and bosentan and 22 sessions of immunoadsorption, his condition improved significantly and he continues in clinical remission. At the time of writing no further immunosuppressive therapy or immunoadsorption had been necessary. The patient is now 15 years old and healthy with an age-based constitution comparable to the normal population.