M04.8 ICD-10-CM Code: Other autoinflammatory syndromes
M04.8 maps to CMS-HCC V28 94. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Autoinflammatory syndromes (M04)
M04.8
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther autoinflammatory syndromes
Other rare genetic conditions characterized by abnormal immune system activation that causes recurrent inflammation and fever not classified elsewhere.
Buddy Insight
This represents other autoinflammatory syndromes not elsewhere classified, including rare genetic conditions characterized by abnormal activation of the innate immune system.
CMS-HCC V28
MappedHCC 94
Coefficient HCC 94: 0.268 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 057
Code-level coefficient reference
ESRD/PACE
MappedHCC 40
Code-level coefficient reference
RXHCC
MappedHCC 83
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Blau syndrome
- Deficiency of interleukin 1 receptor antagonist [DIRA]
- Majeed syndrome
- Periodic fever, aphthous stomatitis, pharyngitis, and adenopathy syndrome [PFAPA]
- Pyogenic arthritis, pyoderma gangrenosum, and acne syndrome [PAPA]
Excludes 2
Official- arthropathic psoriasis (L40.5-)Inherited from M00-M99, M04
- certain conditions originating in the perinatal period (P04-P96)Inherited from M00-M99, M04
- certain infectious and parasitic diseases (A00-B99)Inherited from M00-M99, M04
- compartment syndrome (traumatic) (T79.A-)Inherited from M00-M99, M04
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from M00-M99, M04
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from M00-M99, M04
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from M00-M99, M04
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from M00-M99, M04
- neoplasms (C00-D49)Inherited from M00-M99, M04
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from M00-M99, M04
- Crohn's disease (K50.-)Inherited from M00-M99, M04
Related Codes
Includes
OfficialNo Includes notes are included in this display for M04.8. Check the code and parent instructions in the Code Book.
Excludes 1
OfficialNo Excludes 1 notes are included in this display for M04.8. Check the code and parent instructions in the Code Book.
Code First
OfficialNo Code First sequencing instructions are included in this display for M04.8. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for M04.8. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for M04.8. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is M04.8 an HCC code?
Yes. M04.8 (Other autoinflammatory syndromes) maps to HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.268. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: M04.8 is billable and maps to V28 HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M04.8
- Description
- Other autoinflammatory syndromes
- HCC (V28)
- HCC 94 — Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders
- RAF reference coefficient
- 0.268
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work M04.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for M04.8
For M04.8, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
M04.8 is the ICD-10-CM diagnosis code for other autoinflammatory syndromes. Other rare genetic conditions characterized by abnormal immune system activation that causes recurrent inflammation and fever not classified elsewhere. M04.8 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering autoinflammatory syndromes (m04).
Under the CMS-HCC V28 risk adjustment model, M04.8 maps to Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders (HCC 94) with a source-labeled community, non-dual, aged reference coefficient of 0.268. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This is a catch-all code for autoinflammatory syndromes not specifically classified; document the specific syndrome name when possible. For M04.8, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for M04.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This represents other autoinflammatory syndromes not elsewhere classified, including rare genetic conditions characterized by abnormal activation of the innate immune system. These conditions require specialized diagnosis and treatment, often with immunosuppressive or biologic therapies to control inflammation and prevent complications.
Documentation Requirements
- ✓Documentation of specific autoinflammatory syndrome diagnosis
- ✓Evidence of recurrent inflammatory episodes
- ✓Genetic testing results when available and applicable
- ✓Exclusion of infectious and autoimmune causes
- ✓Documentation of characteristic clinical features
- ✓Laboratory evidence of systemic inflammation
- ✓Family history assessment for hereditary patterns
- ✓Response to specific treatments (anti-inflammatory, immunosuppressive)
Commonly Confused Codes
- •M04.1: Periodic fever syndromes (when specific syndrome doesn't fit periodic pattern)
- •M04.2: Cryopyrin-associated periodic syndromes (when not cryopyrin-related)
- •M35.9: Systemic involvement of connective tissue, unspecified (autoimmune vs autoinflammatory)
- •D89.89: Other specified disorders involving the immune mechanism
- •M79.89: Other specified soft tissue disorders