- PAH - Connective Tissue Disease (PAH-CTD): These patients have a confirmed diagnosis of PAH as well as firm evidence to support a diagnosis of a connective tissue disease. In the REVEAL registry, scleroderma-associated PAH accounted for 60% of PAH-CTD . All PAH-CTD cases will be referred by or evaluated by a rheumatologist to ensure a firm diagnosis. While all CTDs can be complicated by PAH, the most common associations are described below.