D89.4Mast cell activation syndrome and related disorders

D89.4 is the ICD-10-CM diagnosis code for mast cell activation syndrome and related disorders. It belongs to category D89 (other disorders involving the immune mechanism, not elsewhere classified), block D80-D89 (certain disorders involving the immune mechanism) and chapter 3 (diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

Within D89 (other disorders involving the immune mechanism, not elsewhere classified), D89.4 is specifically for mast cell activation syndrome and related disorders. Related codes cover Polyclonal hypergammaglobulinemia (D89.0), Cryoglobulinemia (D89.1), hypergammaglobulinemia, unspecified (D89.2), immune reconstitution syndrome (D89.3), other specified disorders involving the immune mechanism, not elsewhere classified (D89.8) and disorder involving the immune mechanism, unspecified (D89.9).

To report this condition, pick the subcode that matches the documentation: D89.40 (unspecified), D89.41 (syndrome), D89.42 (syndrome), D89.43 (activation), D89.44 (tryptasemia) and D89.49 (disorder).

Don't report D89.4 together with the conditions in its Excludes1 note: aggressive systemic mastocytosis (C96.21), congenital cutaneous mastocytosis (Q82.2), (non-congenital) cutaneous mastocytosis (D47.01), (indolent) systemic mastocytosis (D47.02) and 7 more.

It was added in FY2017, effective October 1, 2016.