Hereditary angioedema (HAE) is a rare, life-threatening disease. The knowledge about
the molecular pathogenesis of HAE has derived mainly from investigating blood samples.
However, limited data are available on the role of the molecular mechanisms in the
affected tissues during HAE attack.The aim of our study was to explore the histological
changes occurring in HAE attacks.Post mortem macro-, microscopic and immunohistological
assessment of upper airway tissues of a patient with HAE due to C1 inhibitor deficiency
(C1-INH-HAE) type 2 who died from laryngeal HAE attack was compared with a non-HAE
patient who died from other condition without any signs of angioedema.Compared to
the control patient, we demonstrated stronger T cell/monocyte infiltration and a more
intense C1-INH staining in the C1-INH-HAE patient. The expression of both bradykinin
receptors (B1/B2) was observed with a slightly lower level in the C1-INH-HAE patient
than in the control patient. PAR1 expression was strongly reduced in the C1-INH-HAE
patient suggesting overactivation of this hyperpermeability inducing receptor.Our
unique case and novel results correspond to the knowledge about C1-INH and BDKRs observed
in plasma; however, it revealed new information about the pathomechanism of HAE attack
focusing on the potential involvement of PAR1 in edema formation. This observation,
if it is verified by subcutaneous biopsy studies, may designate a new therapeutic
target in HAE.
