Hypereosinophilic syndrome [HES], unspecified

This code represents a rare, chronic, and often life-threatening disorder characterized by persistent and unexplained overproduction of eosinophils (a type of white blood cell) in the blood and/or tissues. This eosinophilia can lead to organ damage, particularly affecting the heart, skin, lungs, and nervous system. The "unspecified" designation indicates that the specific subtype or cause of HES has not been determined.

Use this code when documentation confirms a diagnosis of hypereosinophilic syndrome, but the physician has not specified a particular variant (e.g., myeloproliferative, lymphocytic, idiopathic). This code is appropriate when the diagnostic workup for HES is ongoing or when the specific etiology remains unknown. Documentation should clearly indicate persistent eosinophilia and associated organ involvement consistent with HES.

• Do not use this code if a more specific type of hypereosinophilic syndrome (e.g., myeloproliferative HES) is documented.
• Always sequence this code as a primary diagnosis when HES is the reason for the encounter.
• Ensure documentation supports the "unspecified" nature; if a specific cause or subtype is identified, a more precise code should be used.