What is ICD-10 code H21.331?

H21.331 is the ICD-10-CM diagnosis code for Parasitic cyst of iris, ciliary body or anterior chamber, right eye. A fluid-filled sac caused by a parasite in the iris, ciliary body, or front chamber of the right eye. H21.331 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. H21.331 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. H21.331 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. H21.331 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does H21.331 map to under V28?

H21.331 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

What RAF reference is published for H21.331?

H21.331 has no V28 reference coefficient because the final FY2026 source verifies no payable V28 mapping.

What is the V28 vs V24 difference for H21.331?

H21.331 has verified no payable V28 mapping in the final FY2026 source. Select a historical effective period before making any V24 comparison.

What documentation supports H21.331?

Verify documentation specifies parasitic origin to distinguish from non-parasitic cysts Confirm laterality is documented as right eye; use H21.339 if eye not specified H21.331 is not a CMS-HCC V28 payment code in the verified current source, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

2026 ICD-10-CM H21.331: Parasitic cyst of iris, ciliary body

H21.331 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools

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Code lookupH21.331

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the eye and adnexa (H00-H59) / Disorders of sclera, cornea, iris and ciliary body (H15-H22)

H21.331

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Parasitic cyst of iris, ciliary body or anterior chamber, right eye

A fluid-filled sac caused by a parasite in the iris, ciliary body, or front chamber of the right eye.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

N/A

—

Not risk-adjusted for this model/period.

Not mapped

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

H21.3Cyst of iris, ciliary body and anterior chamber H21.33Parasitic cyst of iris, ciliary body or anterior chamber H21.331Parasitic cyst of iris, ciliary body or anterior chamber, right eye

Inclusion Terms

Official

No inclusion terms are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Excludes 2

Official

certain conditions originating in the perinatal period (P04-P96)Inherited from H00-H59, H21, H21.3
certain infectious and parasitic diseases (A00-B99)Inherited from H00-H59, H21, H21.3
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from H00-H59, H21, H21.3
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from H00-H59, H21, H21.3
diabetes mellitus related eye conditions (E09.3-, E10.3-, E11.3-, E13.3-)Inherited from H00-H59, H21, H21.3
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from H00-H59, H21, H21.3
injury (trauma) of eye and orbit (S05.-)Inherited from H00-H59, H21, H21.3
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from H00-H59, H21, H21.3
neoplasms (C00-D49)Inherited from H00-H59, H21, H21.3
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from H00-H59, H21, H21.3
syphilis related eye disorders (A50.01, A50.3-, A51.43, A52.71)Inherited from H00-H59, H21, H21.3
sympathetic uveitis (H44.1-)Inherited from H00-H59, H21, H21.3
miotic pupillary cyst (H21.27-)Inherited from H00-H59, H21, H21.3

Related Codes

Official

H21.332Parasitic cyst of iris, ciliary body or anterior chamber, left eye H21.333Parasitic cyst of iris, ciliary body or anterior chamber, bilateral H21.339Parasitic cyst of iris, ciliary body or anterior chamber, unspecified eye

Includes

Official

No Includes notes are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for H21.331. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Verify documentation specifies parasitic origin to distinguish from non-parasitic cysts

Confirm laterality is documented as right eye; use H21.339 if eye not specified

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 H21.331 an HCC code?

No. H21.331 is a billable ICD-10-CM code with no mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models.

Code: H21.331
Description: Parasitic cyst of iris, ciliary body or anterior chamber, right eye
HCC (V28): No CMS-HCC V28 mapping
RAF reference coefficient: —
Billable: Yes
Payment year: 2026

Coder workflow notes

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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).

What This Code Means

H21.331 is the ICD-10-CM diagnosis code for parasitic cyst of iris, ciliary body or anterior chamber, right eye. A fluid-filled sac caused by a parasite in the iris, ciliary body, or front chamber of the right eye. H21.331 sits in the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59), within the section covering disorders of sclera, cornea, iris and ciliary body (h15-h22).

H21.331 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.

Verify documentation specifies parasitic origin to distinguish from non-parasitic cysts.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for H21.331 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify documentation specifies parasitic origin to distinguish from non-parasitic cysts
•Confirm laterality is documented as right eye; use H21.339 if eye not specified