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Chapters ENES DE

04Diseases of the immune system

4A20 category

Acquired immunodeficiencies

5 subordinate codes

4A20.0Adult-onset immunodeficiency
4A20.1Acquired immunodeficiency due to loss of immunoglobulin
4A20.2Secondary haemophagocytic lymphohistiocytosis
4B4YOther specified diseases of the immune system
4B4ZDiseases of the immune system, unspecified

Nearby in Diseases of the immune system

4A00-4A0ZPrimary immunodeficiencies
4A40-4A4ZNonorgan specific systemic autoimmune disorders
4A60-4A6ZAutoinflammatory disorders
4A80-4A8ZAllergic or hypersensitivity conditions
4B00-4B0ZImmune system disorders involving white cell lineages
4B20-4B2YCertain disorders involving the immune system
4B40Diseases of thymus
Organ specific autoimmune disorders

Previous4A00-4A0Z — Primary immunodeficiencies Next4A40-4A4Z — Nonorgan specific systemic autoimmune disorders

Browse ICD-11

01Certain infectious or parasitic diseases
02Neoplasms
03Diseases of the blood or blood-forming organs
04Diseases of the immune system
05Endocrine, nutritional or metabolic diseases
06Mental, behavioural or neurodevelopmental disorders
07Sleep-wake disorders
08Diseases of the nervous system
09Diseases of the visual system
10Diseases of the ear or mastoid process
11Diseases of the circulatory system
12Diseases of the respiratory system
13Diseases of the digestive system
14Diseases of the skin
15Diseases of the musculoskeletal system or connective tissue
16Diseases of the genitourinary system
17Conditions related to sexual health
18Pregnancy, childbirth or the puerperium
19Certain conditions originating in the perinatal period
20Developmental anomalies
21Symptoms, signs or clinical findings, not elsewhere classified
22Injury, poisoning or certain other consequences of external causes
23External causes of morbidity or mortality
24Factors influencing health status or contact with health services
25Codes for special purposes
26Supplementary Chapter Traditional Medicine Conditions
VSupplementary section for functioning assessment
XExtension Codes
4A00-4A0ZPrimary immunodeficiencies
4A20Acquired immunodeficiencies
4A40-4A4ZNonorgan specific systemic autoimmune disorders
4A60-4A6ZAutoinflammatory disorders
4A80-4A8ZAllergic or hypersensitivity conditions
4B00-4B0ZImmune system disorders involving white cell lineages
4B20-4B2YCertain disorders involving the immune system
4B40Diseases of thymus
Organ specific autoimmune disorders
4B4YOther specified diseases of the immune system
4B4ZDiseases of the immune system, unspecified
4A20.0Adult-onset immunodeficiency
4A20.1Acquired immunodeficiency due to loss of immunoglobulin
4A20.2Secondary haemophagocytic lymphohistiocytosis
4B4YOther specified diseases of the immune system
4B4ZDiseases of the immune system, unspecified

International Classification of Diseases, Eleventh Revision (ICD-11), World Health Organization (WHO) 2019/2021, https://icd.who.int/browse11. Licensed under Creative Commons Attribution-NoDerivatives 3.0 IGO (CC BY-ND 3.0 IGO).

Release 2026-01. View this entity in the official WHO ICD-11 browser.

This page reproduces WHO classification content for reference. It is not medical advice and must not be used to diagnose or treat. For coding decisions, consult the official release and your national coding guidelines.

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