Partial loss of TYK2 function is associated with reduced risk for several autoimmune disorders such as RA and psoriatic disease, conditions treated with immunosuppressive therapy.13,29–32 Humans with complete TYK2 loss of function have clinically significant immunodeficiency with increased susceptibility to mycobacterial and viral infections.28,33 In line with the TYK2 findings is enhanced steroid responsiveness among patients with asthma carrying the CRHR1 variant34. This evidence concerns the gene TYK2 and immunodeficiency disease.