ICD code M04.8 – Other autoinflammatory syndromes

Key takeaways

M04.8 is the billable ICD-10-CM code for other autoinflammatory syndromes, valid for FY2026 from October 1, 2025

Five conditions are named under M04.8: Blau syndrome, DIRA, Majeed syndrome, PFAPA syndrome and PAPA syndrome

Category M04 holds only four codes, M04.1, M04.2, M04.8 and M04.9. There is no M04.3 and no M04.4

TRAPS, hyperimmunoglobulin D syndrome, mevalonate kinase deficiency and familial Mediterranean fever all route to M04.1

M04 carries an Excludes2 note for Crohn’s disease (K50.-), so M04.8 and a K50 code can be reported together

ICD-10 code M04.8: definition and billable status

ICD-10 code M04.8 is the billable ICD-10-CM code for other autoinflammatory syndromes. It is one of four active codes in category M04, and it carries five named conditions of its own. Per the CDC/NCHS ICD-10-CM web tool, M04.8 is both billable and specific, so it can stand as the primary diagnosis on a professional claim.

The CMS ICD-10 codes page confirms that the FY2026 update files carry M04.8 with no change to its description or billable status. Coders should still re-check the M04 block each October, because a new subcategory would narrow what the residual “other” code is allowed to absorb.

Clinical description: what conditions does M04.8 cover?

M04.8 covers five named autoinflammatory conditions. ICD-10-CM lists them under the code directly: Blau syndrome, deficiency of interleukin 1 receptor antagonist (DIRA), Majeed syndrome, PFAPA syndrome, and PAPA syndrome. These are not leftovers. Each one is a recognized syndrome that the tabular list files under M04.8 rather than giving it a code of its own.

Autoinflammatory syndromes are disorders of the innate immune system. They produce recurrent episodes of systemic inflammation, fever, serositis, and organ-specific findings, without the autoantibodies or antigen-specific T-cell response that mark autoimmune disease. Documentation for M04.8 has to reflect that innate-immune picture, since autoimmune arthropathies are classified elsewhere in ICD-10-CM.

• Blau syndrome: NOD2-associated granulomatous arthritis, uveitis, and dermatitis, usually with onset in early childhood
• Deficiency of interleukin 1 receptor antagonist (DIRA): neonatal-onset pustulosis and sterile multifocal osteomyelitis driven by unopposed IL-1 signaling
• Majeed syndrome: chronic recurrent multifocal osteomyelitis with congenital dyserythropoietic anemia
• PFAPA syndrome: periodic fever with aphthous stomatitis, pharyngitis, and adenitis, the most common periodic fever picture in young children
• PAPA syndrome: pyogenic sterile arthritis with pyoderma gangrenosum and acne

Two further groups land on M04.8 in practice. The first is an undifferentiated systemic autoinflammatory disease, where the phenotype is documented but genetic testing has not assigned a named syndrome. The second is a newly described entity that has no code of its own yet. Both need the physician to state an autoinflammatory diagnosis in the record before the code is assigned.

Watch the routing in the other direction as well. Familial Mediterranean fever, hyperimmunoglobulin D syndrome, mevalonate kinase deficiency, and TRAPS are all inclusion terms under ICD-10 code M04.1. None of them belongs on M04.8, and the cryopyrin-associated syndromes go to M04.2.

Includes and excludes notes for M04.8

The tabular list attaches instructional notes at two levels here. M04.8 carries its own inclusion terms, while the Excludes2 note sits one level up at the M04 category and therefore applies to M04.8 as well.

Inclusion terms listed under M04.8

An inclusion term is a diagnosis the code set has already routed for you. When the physician documents one of the five terms below, M04.8 is the correct assignment and no physician query is needed to justify the choice.

• 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]

Excludes2: Crohn’s disease (K50.-)

Category M04 carries a single Excludes2 note, for Crohn’s disease (K50.-). An Excludes2 note means the excluded condition is not part of what M04 represents, but a patient can have both. When the record documents Crohn’s disease alongside a separate autoinflammatory syndrome, report both codes on the claim.

That distinction matters at the claim edit level. An Excludes1 note would block the pairing outright and generate a rejection. M04’s note is an Excludes2. A claim carrying M04.8 and a K50 code together is valid, as long as both diagnoses are documented separately.

Synonyms and approximate terms for M04.8

Records rarely use the tabular list’s exact wording. The table below maps the phrases that turn up in referral letters, rheumatology notes, and discharge summaries to the coding decision each one should trigger.

Be careful with “periodic fever” on its own. The AAPC listing for M04.1 shows that the phrase maps to the periodic fever syndromes code, not to M04.8. PFAPA is the one periodic fever picture that does belong on M04.8, and only because the tabular list names it there.

M04.8 in context: the M04 autoinflammatory syndromes category

M04.8 is one of four active codes in the M04 category. The block is smaller than coders often assume, and the numbering skips: there is no M04.0, and nothing exists between M04.2 and M04.8. The table below shows the full FY2026 sibling set.

The hierarchy follows standard ICD-10-CM convention. A documented syndrome that appears as an inclusion term goes to the code that names it. A documented autoinflammatory disease with no named subtype goes to M04.8. Only a bare “autoinflammatory syndrome” with no further detail goes to ICD-10 code M04.9. A physician query is usually worth raising before that claim goes out.

When M04.8 does and does not apply

• Use M04.8: the record documents Blau syndrome, DIRA, Majeed syndrome, PFAPA, or PAPA. It also applies to a systemic autoinflammatory disease that meets no named subtype in M04.1 or M04.2
• Do not use M04.8: when FMF, HIDS, mevalonate kinase deficiency, or TRAPS is documented, since all four are inclusion terms at M04.1. A documented cryopyrin-associated syndrome goes to M04.2 instead
• Query the physician: records reading “possible autoinflammatory syndrome” or “suspected periodic fever” without a confirmed diagnosis. Query also where the named syndrome is classified outside the M04 block

Coding guidelines and documentation requirements for M04.8

Accurate coding of M04.8 depends on what the treating physician documents, not on the coder’s clinical judgment. The ICD-10-CM Official Guidelines for Coding and Reporting, maintained by CMS and the NCHS, require diagnosis codes to reflect a confirmed diagnosis. For M04.8, that means a named inclusion term in the record. Failing that, it means an explicit statement of a systemic autoinflammatory syndrome outside M04.1 and M04.2.

Payer coverage attached to an M04.8 diagnosis varies widely. Some commercial plans apply medical necessity criteria that call for genetic testing results or a documented specialist evaluation before they authorize treatment. Verify the individual payer’s policy rather than assuming coverage, and confirm that medical billing compliance requirements are met before the claim goes out.

Documentation checklist for M04.8

• The physician’s confirmed diagnosis of an autoinflammatory syndrome, stated as confirmed rather than probable, suspected, or rule-out
• The specific syndrome name where one applies, since Blau, DIRA, Majeed, PFAPA, and PAPA are inclusion terms that support M04.8 on their own
• For an unnamed presentation, a statement that the periodic fever syndromes at M04.1 and the cryopyrin-associated syndromes at M04.2 were considered and do not apply
• Clinical findings consistent with systemic autoinflammatory disease: recurrent fever episodes, serositis, raised acute-phase reactants, or organ-specific inflammation
• Genetic testing results where they exist, recorded in the chart even when the result is inconclusive
• Specialist involvement noted, whether rheumatology, immunology, or a pediatric subspecialty
• Absence of autoantibody findings or an autoimmune disease pattern, which separates autoinflammatory from autoimmune

Those elements need to be in the chart before the claim leaves the practice. Practices submitting electronic claims via Claim.MD, Pabau’s US clearinghouse partner, get the code validated against the FY2026 tabular list before transmission. The clean claim requirements are the same as for any diagnosis. The code must be billable, the documentation must support it, and the claim must match the record.

How to document M04.8 for accurate claim submission

Rheumatology and pediatric practices coding autoinflammatory syndromes need a repeatable sequence. The five steps below follow the coding logic for an M04.8 claim from note to submission.

1. Confirm the diagnosis is established: check that the physician documented a confirmed autoinflammatory syndrome in the encounter note or problem list, not a suspected one
2. Check the inclusion terms first: Blau syndrome, DIRA, Majeed syndrome, PFAPA, and PAPA are named under M04.8, so any of them settles the assignment immediately
3. Rule out the two named siblings: M04.1 takes FMF, HIDS, mevalonate kinase deficiency, and TRAPS, while M04.2 takes the cryopyrin-associated syndromes
4. Verify FY2026 validity: confirm the service date falls on or after October 1, 2025, the point at which the FY2026 code set took effect
5. Submit through a validated clearinghouse: Pabau’s claims management software carries a built-in ICD-10 catalogue, so code-level errors surface before the payer sees them

The EHR integration behind those steps is where code-to-documentation alignment holds up best. When the coder picks the ICD-10 code inside the same system that holds the clinical note, nothing gets re-keyed between tabs.

Associated CPT and HCPCS codes for autoinflammatory syndrome care

M04.8 is a diagnosis code, so it never appears alone on a professional claim. It supports the procedure and drug codes reported for the encounter. The table below lists the codes that most often accompany an autoinflammatory syndrome visit.

One caveat is worth flagging to the billing team. The labeled indications for the IL-1 inhibitors sit mainly with the syndromes coded at M04.1 and M04.2. A payer reviewing a drug claim carried by M04.8 will often ask for the clinical rationale. Expect a prior authorization request, and have the specialist’s note ready before the drug is administered.

Common coding errors with M04.8

Most M04.8 problems trace back to the same handful of habits. Each one below is worth building into a pre-submission check.

• Coding TRAPS or HIDS to a subcategory that does not exist: reference tools and older training decks sometimes show M04.3 or M04.4. Neither code is in ICD-10-CM. Both syndromes belong on M04.1
• Sending PFAPA to M04.9: PFAPA is a named inclusion term at M04.8, so an unspecified code understates the documentation that already exists
• Defaulting to M04.8 for a bare “periodic fever”: that phrase points to M04.1, and an unconfirmed presentation may need a symptom code instead
• Treating the Crohn’s disease note as Excludes1: M04’s note is an Excludes2, so M04.8 and a K50 code can be reported together
• Reaching for M04.9 out of caution: an unspecified code invites medical necessity review on rare disease claims. M04.8 is available once the record identifies the condition as autoinflammatory

M04.8 code history and annual updates

M04.8 has held the same descriptor and billable status since the M04 category was created. The table below summarizes the code’s history.

The category has been stable since then, which is part of why the four-code structure is worth memorizing. Practices should still review the ICD-10-CM update files each October. If a new subcategory is ever added to M04, conditions currently sitting on M04.8 would move. A static code list would keep sending the old code.

Clearinghouse submission and reimbursement considerations

M04.8 is billable, so it can be reported as a primary or secondary diagnosis on a professional claim. Payer coverage policies still vary a great deal. Some commercial plans use the M04.8 diagnosis itself as the trigger for prior authorization on specialist visits, infusion therapy, or biologic agents.

For practices submitting through Pabau, the clearinghouse claim submission process validates ICD-10-CM codes against the current tabular list before transmission. Electronic remittance advice on M04.8 claims should be read for denial reasons in the “diagnosis not covered” and “medical necessity” families.

Practices with recurring M04.8 claims benefit from tracking those denials by reason code. Rare disease codes attract more scrutiny than routine ones, and a pattern by payer is easier to fix than a run of one-off appeals. That is ordinary revenue cycle management work, applied to a low-volume code.

How Pabau supports M04.8 coding and claim submission

Most M04.8 errors start outside the chart. A coder opens a reference site in a second tab. The list there may include subcategories ICD-10-CM never published. The result then gets typed into the claim by hand. The syndrome names in category M04 are long, the block is small, and a single mis-typed digit produces a code that does not exist.

Practice management software like Pabau closes that loop by keeping the code search inside the clinical record. Staff search the ICD-10-CM catalogue from within the encounter and attach M04.8 to the note it belongs to. The code then carries through to the claim. Because the catalogue is maintained against the current tabular list, an invalid entry such as M04.3 has nowhere to enter the workflow.

Claims then go out through Claim.MD, Pabau’s US clearinghouse partner, which validates each code before transmission. Denials come back into the same system, so denial management happens against the original documentation rather than a spreadsheet. For a rheumatology practice running a handful of autoinflammatory patients, that means fewer rejections on codes nobody bills often enough to memorize.

Stop copying M04.8 from a reference tab into your EHR

Pabau puts the ICD-10-CM catalogue inside the clinical workflow. Search, select, and submit M04.8 without leaving the platform. Claim.MD clearinghouse integration validates every code against the FY2026 tabular list before transmission.

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Conclusion

ICD-10 code M04.8 covers five named autoinflammatory syndromes, Blau, DIRA, Majeed, PFAPA, and PAPA, plus documented autoinflammatory disease that meets no named subtype. Category M04 holds four codes in total, not six. The subcategories M04.3 and M04.4 do not exist. The most common M04.8 error is an attempt to route TRAPS or hyperimmunoglobulin D syndrome away from M04.1. That is where the tabular list puts both.

Get the routing right and the documentation follows easily. Name the syndrome where the record names one. Where none is named, state that M04.1 and M04.2 were considered. Remember, too, that the Crohn’s disease note is an Excludes2, so both codes can appear on one claim.

Pabau keeps that lookup inside the record and validates the code through Claim.MD before the claim leaves the practice. To see how it would work in your billing setup, book a demo.

Continue your research

Need to verify ICD-10 codes before claim submission? Claims management software covers how Pabau validates diagnosis codes at the point of claim creation.

Confused about which clearinghouse handles autoinflammatory syndrome claims? Medical claims clearinghouse guide explains how clearinghouses process ICD-10-coded professional claims.

Want to reduce denials on rare diagnosis codes? Denial codes in medical billing maps the most common payer rejection codes and how to respond.

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