E31.21 Multiple endocrine neoplasia [MEN] type I

Billable ICD-10-CM code, FY2026.

Applicable to

• Wermer's syndrome

Applies from E31 Polyglandular dysfunction

Excludes1 (never code together)

• ataxia telangiectasia [Louis-Bar] (G11.3)
• dystrophia myotonica [Steinert] (G71.11)
• pseudohypoparathyroidism (E20.1)

Applies from E31.2 Multiple endocrine neoplasia [MEN] syndromes

Applicable to

• Multiple endocrine adenomatosis

Code also

• any associated malignancies and other conditions associated with the syndromes

Risk adjustment (HCC)

• CMS-HCC V28: HCC 51 — Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders
• CMS-HCC V22: HCC 23 — Other Significant Endocrine and Metabolic Disorders
• RxHCC V08: HCC 43 — Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders
• ESRD V24: HCC 23

MS-DRG index

Defines the logic of DRG(s) 643-645 in MDC 10.

Approximate ICD-9-CM (GEMs)

• 258.01 Multiple endocrine neoplasia [MEN] type I

Code annotations containing back-references to E31.21

Back-references to E31.2

• Code Also: C7A Malignant neuroendocrine tumors ("any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-)")
• Code Also: D3A Benign neuroendocrine tumors ("any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-)")
• Type 1 Excludes: D44 Neoplasm of uncertain behavior of endocrine glands ("multiple endocrine adenomatosis (E31.2-)")
• Type 1 Excludes: D44 Neoplasm of uncertain behavior of endocrine glands ("multiple endocrine neoplasia (E31.2-)")
• Type 1 Excludes: E31.1 Polyglandular hyperfunction ("multiple endocrine adenomatosis (E31.2-)")
• Type 1 Excludes: E31.1 Polyglandular hyperfunction ("multiple endocrine neoplasia (E31.2-)")
• Type 1 Excludes: Z15.81 Genetic susceptibility to multiple endocrine neoplasia [MEN] ("multiple endocrine neoplasia [MEN] syndromes (E31.2-)")

Back-references to E31

• Code First: G63 Polyneuropathy in diseases classified elsewhere ("endocrine disease, except diabetes (E00-E07, E15-E16, E20-E34)")

Diagnosis Index entries for E31.21

• Disease, diseased › Wermer's
• Neoplasia › endocrine, multiple (MEN) › type I
• Syndrome › Wermer's
• Wermer's disease or syndrome

Nearby codes

• E31 Polyglandular dysfunction
• E31.0 Autoimmune polyglandular failure
• E31.1 Polyglandular hyperfunction
• E31.2 Multiple endocrine neoplasia [MEN] syndromes
• E31.20 Multiple endocrine neoplasia [MEN] syndrome, unspecified
• E31.21 Multiple endocrine neoplasia [MEN] type I (this code)
• E31.22 Multiple endocrine neoplasia [MEN] type IIA
• E31.23 Multiple endocrine neoplasia [MEN] type IIB
• E31.8 Other polyglandular dysfunction
• E31.9 Polyglandular dysfunction, unspecified