MCHR1, a plasma membrane protein that inhibits cAMP accretion and induces intracellular calcium flux, was exclusively downregulated in AA-SScL fibroblasts, a finding that contrasts with the upregulation of MCHR1 observed in IPF [107], which has pathologic features overlapping with SSc-PF. The gene discussed is MCHR1; the disease is pemphigus foliaceus.