Pulse methylprednisolone in allergic bronchopulmonary aspergillosis exacerbations.

and the penetrance is highly variable. It has been suggested that a ‘‘second hit’’ is required to precipitate the phenotype and could cause further deregulation of BMPR2/Smad signalling, leading to PAH [9, 10]. Although the significance of gremlin levels in PAH has yet to be determined, in a mutation carrier developing IPF, hypoxia or increased gremlin levels may account for a second insult, leading to the manifestation of PAH.