M30.3

M30.3 identifies Kawasaki disease — an acute systemic vasculitis affecting medium-sized arteries, classified under polyarteritis nodosa and related conditions in the musculoskeletal and connective tissue chapter.

Verified May 8, 2026 · 6 sources ↓

Status: Billable
Chapter: 13
Related CPT: 0
Region: General

Drawn from CDCICD10DataAAPCIcdcodesIcdlist

Documentation tips

What should appear in the chart to support M30.3.

Source · Editorial brief grounded in 6 cited references ↓

Record fever duration explicitly (≥5 days is a clinical validation threshold for Kawasaki diagnosis).
List each principal clinical feature present — conjunctivitis, rash, oral mucosa changes, extremity erythema/edema, and cervical lymphadenopathy — so the diagnosis is clinically supported in the note.
Include echocardiogram results, especially any coronary artery abnormalities, and laboratory findings (CRP, ESR) that support the diagnosis.
Provider must state a confirmed diagnosis of Kawasaki disease; 'suspected' or 'rule-out' Kawasaki does not support M30.3 in an outpatient setting.
If coronary artery aneurysm is identified as a direct complication, document it as such — it is captured within M30.3's synonym set and does not require a separate aneurysm code unless independently significant.

Common coding pitfalls

The recurring mistakes coders make with M30.3 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Assigning M30.3 on clinical suspicion alone in an outpatient setting — the provider must document a confirmed diagnosis.
Coding M30.3 alongside M31.7 (microscopic polyarteritis), which is prohibited by the Excludes1 note on the parent category M30.
Defaulting to a symptom-level code (fever, rash, lymphadenopathy) when the provider has already documented a confirmed Kawasaki diagnosis — M30.3 subsumes those manifestations.
Confusing Kawasaki disease with scarlet fever (A38.9) or toxic shock syndrome (A48.4) when documentation is ambiguous — query the provider rather than assuming M30.3.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

M30.3 is the single billable code for Kawasaki disease (mucocutaneous lymph node syndrome). Use it when a provider has documented a confirmed diagnosis of Kawasaki disease, characterized by prolonged fever (≥5 days), at least four of the five principal clinical features (rash, conjunctivitis, oral mucosa changes, extremity changes, cervical lymphadenopathy), and supporting laboratory or echocardiographic findings. It is not a code to assign on clinical suspicion alone — the diagnosis must be established by the treating physician.

M30.3 sits within category M30 (Polyarteritis nodosa and related conditions). The parent category carries an Excludes1 note for microscopic polyarteritis (M31.7), meaning M30.3 and M31.7 cannot be coded together. When coronary artery aneurysm is documented as a complication of Kawasaki disease, that finding is captured by the 'aneurysm of coronary artery due to acute febrile mucocutaneous lymph node syndrome' synonym already embedded in M30.3 — a separate coronary aneurysm code is not required unless the clinical scenario demands independent reporting of a distinct cardiac finding.

Differential coding matters here: toxic shock syndrome (A48.4) and scarlet fever (A38.9) can mimic Kawasaki disease clinically. If the provider documents hypotension with multi-organ involvement and no coronary changes, consider A48.4. A positive strep culture with sandpaper rash points to A38.9. Do not assign M30.3 in the absence of explicit provider confirmation of the Kawasaki diagnosis.

Sibling codes

Other billable codes under M30 (laterality / anatomic variants).

M30.0

Polyarteritis nodosa

M30.1

Polyarteritis with lung involvement [Churg-Strauss]

M30.2

Juvenile polyarteritis

M30.8

Other conditions related to polyarteritis nodosa

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01Is M30.3 the only code needed when Kawasaki disease causes a coronary artery aneurysm?

In most cases, yes. Coronary aneurysm due to Kawasaki disease is listed as an approximate synonym of M30.3, so the complication is captured within the same code. Add a separate cardiac code only if the aneurysm requires independent clinical tracking or the payer specifically requires it.

02Can M30.3 be used for an adult patient?

Yes — M30.3 carries no age restriction in ICD-10-CM. Kawasaki disease is most common in children under 5, but the code is valid for any age group when the provider confirms the diagnosis.

03What codes are excluded from being reported with M30.3?

The parent category M30 carries an Excludes1 note for microscopic polyarteritis (M31.7). Excludes1 means these two conditions cannot be coded together — they are mutually exclusive by ICD-10-CM convention.

04How should M30.3 be coded when Kawasaki disease is suspected but not confirmed in an outpatient setting?

Do not assign M30.3 for a suspected or rule-out diagnosis in the outpatient setting. Code the presenting signs and symptoms (fever, rash, lymphadenopathy) until the provider documents a confirmed diagnosis per ICD-10-CM outpatient guidelines.

05Is a 7th character required for M30.3?

No. M-codes in Chapter 13 do not use 7th-character extensions. The 7th-character encounter designators (A, D, S) apply to injury S-codes, not to systemic disease codes like M30.3.

06What distinguishes M30.3 from M30.2 (juvenile polyarteritis)?

M30.2 identifies juvenile polyarteritis nodosa — a distinct vasculitis involving small and medium arteries without the mucocutaneous features of Kawasaki disease. M30.3 is specifically reserved for Kawasaki disease with its defined clinical criteria. The provider's confirmed diagnosis determines which code applies.

07Which differential diagnoses should be ruled out before assigning M30.3?

Toxic shock syndrome (A48.4) and scarlet fever (A38.9) are the primary differentials. A positive strep culture with sandpaper rash supports A38.9. Hypotension and multi-organ involvement without coronary changes suggests A48.4. Query the provider if the clinical picture is ambiguous.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira's AI scribe captures fever duration, each principal clinical feature by name, CRP/ESR values, and echocardiogram findings (including any coronary artery abnormalities) from the encounter note. That structured capture prevents unspecified or symptom-level coding when the provider has confirmed Kawasaki disease, and eliminates the audit risk of assigning M30.3 without clinical validation criteria documented in the record.

See how Mira captures M30.3 documentation