What is ICD-10 code J66.1?

J66.1 is the ICD-10-CM diagnosis code for Flax-dressers' disease. A respiratory disease that affects workers who process flax fibers, caused by inhaling flax dust and resulting in airway inflammation and breathing problems. It belongs to the ICD-10-CM chapter for diseases of the respiratory system (j00-j99). J66.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. J66.1 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. J66.1 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. J66.1 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 J66.1 map to under V28?

J66.1 maps to CMS-HCC V28 HCC 280 (Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM J66.1: Flax-dressers' disease

J66.1 maps to CMS-HCC V28 280. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupJ66.1

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the respiratory system (J00-J99) / Lung diseases due to external agents (J60-J70)

J66.1

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

Flax-dressers' disease

A respiratory disease that affects workers who process flax fibers, caused by inhaling flax dust and resulting in airway inflammation and breathing problems.

Buddy Insight

Flax-dressers' disease is a specific occupational respiratory condition caused by flax fiber processing, representing a form of byssinosis with distinct exposure characteristics.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 280

Chronic Obstructive Pulmonary...

Code-level coefficient reference

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

Mapped

HCC 162

HHS-HCC 162 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 112

Fibrosis of Lung and Other Ch...

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

J66Airway disease due to specific organic dust J66.1Flax-dressers' disease

Inclusion Terms

Official

No inclusion terms are included in this display for J66.1. Check the code and parent instructions in the Code Book.

Excludes 2

Official

certain conditions originating in the perinatal period (P04-P96)Inherited from J00-J99, J60-J70, J66
certain infectious and parasitic diseases (A00-B99)Inherited from J00-J99, J60-J70, J66
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from J00-J99, J60-J70, J66
congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from J00-J99, J60-J70, J66
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from J00-J99, J60-J70, J66
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from J00-J99, J60-J70, J66
neoplasms (C00-D49)Inherited from J00-J99, J60-J70, J66
smoke inhalation (T59.81-)Inherited from J00-J99, J60-J70, J66
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from J00-J99, J60-J70, J66
asthma (J45.-)Inherited from J00-J99, J60-J70, J66
malignant neoplasm of bronchus and lung (C34.-)Inherited from J00-J99, J60-J70, J66
allergic alveolitis (J67.-)Inherited from J00-J99, J60-J70, J66
asbestosis (J61)Inherited from J00-J99, J60-J70, J66
bagassosis (J67.1)Inherited from J00-J99, J60-J70, J66
farmer's lung (J67.0)Inherited from J00-J99, J60-J70, J66
hypersensitivity pneumonitis due to organic dust (J67.-)Inherited from J00-J99, J60-J70, J66
reactive airways dysfunction syndrome (J68.3)Inherited from J00-J99, J60-J70, J66

Related Codes

Official

J66.0Byssinosis J66.2Cannabinosis J66.8Airway disease due to other specific organic dusts

Includes

Official

No Includes notes are included in this display for J66.1. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for J66.1. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for J66.1. Check the code and parent instructions in the Code Book.

Use Additional

Official

code, where applicable, to identify:Inherited from J00-J99
exposure to environmental tobacco smoke (Z77.22)Inherited from J00-J99
exposure to tobacco smoke in the perinatal period (P96.81)Inherited from J00-J99
history of tobacco dependence (Z87.891)Inherited from J00-J99
occupational exposure to environmental tobacco smoke (Z57.31)Inherited from J00-J99
tobacco dependence (F17.-)Inherited from J00-J99
tobacco use (Z72.0)Inherited from J00-J99

Code Also

Official

No Code Also instructions are included in this display for J66.1. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documented occupational exposure specifically to flax dust during dressing or processing operations

Chest imaging and pulmonary function test results

Symptom description including temporal pattern related to work exposure

Duration of occupational exposure to flax processing

MEAT Support

HCC Buddy guidance

Documented occupational exposure specifically to flax dust during dressing or processing operations

Chest imaging and pulmonary function test results

Symptom description including temporal pattern related to work exposure

Duration of occupational exposure to flax processing

Audit Caution

HCC Buddy guidance

Using the broader byssinosis code (J66.0) when flax-specific exposure is documented

Confusing flax dust disease with other textile fiber diseases — the specific fiber matters for coding

Not documenting the specific occupational activity (flax dressing/processing) to support the code

Defaulting to J66.8 when J66.1 is the more specific and appropriate code

Common Mistakes

HCC Buddy guidance

J66.0 (Byssinosis) — broader category including cotton and hemp; J66.1 is specific to flax processing

J66.2 (Cannabinosis) — hemp/cannabis dust, not flax

J66.8 (Airway disease due to other specific organic dusts) — residual category; use J66.1 when flax is identified

J67.8 (Hypersensitivity pneumonitis due to other organic dusts) — different mechanism than byssinosis-type disease

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 J66.1 an HCC code?

Yes. J66.1 (Flax-dressers' disease) maps to HCC 280, Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.319. 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: J66.1 is billable and maps to V28 HCC 280, Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: J66.1
Description: Flax-dressers' disease
HCC (V28): HCC 280 — Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders
RAF reference coefficient: 0.319
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 280, Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders

0.319

ESRDHCC 112, Fibrosis of Lung and Other Chronic Lung Disorders

Not separately weighted

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 J66.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for J66.1

For J66.1, 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

J66.1 is the ICD-10-CM diagnosis code for flax-dressers' disease. A respiratory disease that affects workers who process flax fibers, caused by inhaling flax dust and resulting in airway inflammation and breathing problems. J66.1 sits in the ICD-10-CM chapter for diseases of the respiratory system (j00-j99), within the section covering lung diseases due to external agents (j60-j70).

Under the CMS-HCC V28 risk adjustment model, J66.1 maps to Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders (HCC 280) with a source-labeled community, non-dual, aged reference coefficient of 0.319. No V24 mapping is shown for J66.1; use the applicable model and payment year when reviewing the V28 mapping. 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.

Verify occupational exposure specifically to flax dressing or processing operations. For J66.1, 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 J66.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify occupational exposure specifically to flax dressing or processing operations
•This is a specific occupational disease; ensure documentation clearly indicates flax exposure rather than other textile dusts

Clinical Significance

Flax-dressers' disease is a specific occupational respiratory condition caused by flax fiber processing, representing a form of byssinosis with distinct exposure characteristics. It is relevant for risk adjustment as a chronic occupational lung disease requiring ongoing monitoring, treatment, and potential workplace restrictions.

Documentation Requirements

✓Documented occupational exposure specifically to flax dust during dressing or processing operations
✓Chest imaging and pulmonary function test results
✓Symptom description including temporal pattern related to work exposure
✓Duration of occupational exposure to flax processing
✓Current respiratory status and functional limitations
✓Treatment plan and work modification recommendations

Commonly Confused Codes

•J66.0 (Byssinosis): broader category including cotton and hemp; J66.1 is specific to flax processing
•J66.2 (Cannabinosis): hemp/cannabis dust, not flax
•J66.8 (Airway disease due to other specific organic dusts): residual category; use J66.1 when flax is identified
•J67.8 (Hypersensitivity pneumonitis due to other organic dusts): different mechanism than byssinosis-type disease