2025 ICD-10-CM Diagnosis Code C88.21

Clinical Information

• Heavy Chain Disease

  a disorder of immunoglobulin synthesis in which large quantities of abnormal heavy chains are excreted in the urine. the amino acid sequences of the n-(amino-) terminal regions of these chains are normal, but they have a deletion extending from part of the variable domain through the first domain of the constant region, so that they cannot form cross-links to the light chains. the defect arises through faulty coupling of the variable (v) and constant (c) region genes.

• Immunoproliferative Small Intestinal Disease

  a condition that is caused by hyperplasia of lymphocytes in the small intestine (intestine, small) and the mesenteric lymph nodes. these lymphocytes produce an anomalous alpha heavy chain protein. generally, these ipsid patients have either concurrent lymphoma or develop lymphoma within a few years. the disease was first described in the mediterranean region and is characterized by malabsorption; weight loss; diarrhea; and steatorrhea.

New 2025 ICD-10-CM Code

C88.21 is new to ICD-10-CM code set for the FY 2025, effective October 1, 2024. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2024. This is a new and revised code for the FY 2025 (October 1, 2024 - September 30, 2025).

C88.21 is grouped with Diagnostic Related Groups - MS-DRG Mapping

Diagnosis-Related Groups (DRGs) are used to classify hospital cases for billing and healthcare management. They help standardize how hospitals and other providers are reimbursed for inpatient care. Patients are grouped based on their principal diagnosis into broader categories called Major Diagnostic Categories (MDCs).

Once assigned to a DRG, the hospital receives a set payment for the patient’s care, regardless of the actual services provided. This fixed rate is intended to cover the typical cost of treating patients within that group. The payment amount depends on the DRG's relative weight, which reflects the expected complexity and cost of care based on the severity of the patient’s condition.

Diagnostic related groups encourage healthcare providers to focus on quality and efficiency in patient care while managing costs effectively. The diagnosis code is present in the following groups for version MS-DRG V42.0 applicable from 10/01/2024 through 09/30/2025.

Replacement Code

C8821 replaces the following previously assigned ICD-10-CM code(s):

• Z85.79 - Prsnl hx of malig neoplm of lymphoid, hematpoetc & rel tiss

Code History