The Centers for Medicare & Medicaid Services has finalized the FY 2027 update to the ICD-10-CM code set, and coders need to update themselves in diagnosis codes before it takes effect on October 1, 2026. This release brings 238 new codes, 21 deletions, and four code revisions, along with hundreds of quiet-but-important edits to Excludes notes and Code Also instructions. As always, the goal behind these changes is greater clinical specificity — giving coders codes that match documentation more precisely instead of forcing everything into a vague “unspecified” bucket.
Three chapters saw more changes this cycle: injury and poisoning, pregnancy and childbirth, and musculoskeletal conditions. Below is the chapter-by-chapter breakdown of changes done at code-assignment level. For a broader look at everything included in this release, see this complete FY 2027 ICD-10-CM guide.
Chapter 13: Diseases of the Musculoskeletal System and Connective Tissue (M00–M99)
Musculoskeletal additions this year cluster around two conditions: plantar fasciitis and osteomyelitis.
Plantar fasciitis gets its own dedicated code family under “Disorders of synovium and tendon (M65–M67)”:
- M67.A — Plantar fasciitis
- M67.A0 — Plantar fasciitis, foot
- M67.A01 — Plantar fasciitis, right foot
- M67.A02 — Plantar fasciitis, left foot
- M67.A09 — Plantar fasciitis, unspecified foot
This matters because plantar fasciitis previously had to compete for space under other code families that weren’t a clean clinical match. Giving it its own family reduces ambiguity at the point of code selection.
Related to this, the fibroblastic disorders under M72 are getting a terminology correction. The note under M72.2 (Plantar fascial fibromatosis) is dropping the reference to “Plantar fasciitis” and replacing it with “Ledderhose disease” — the clinically accurate term for the condition, which results from benign fibrous nodules growing along the plantar fascia. Three new laterality codes come with this change:
- M72.20 — Plantar fascial fibromatosis, unspecified foot
- M72.21 — Plantar fascial fibromatosis, right foot
- M72.22 — Plantar fascial fibromatosis, left foot
Coders should also flag the Excludes1 note revision under M72.8 (Other fibroblastic disorders): the old cross-reference to “plantar fasciitis (M72.2)” is being corrected to point to the new M67.A0- family instead. If your encoder or reference material hasn’t been updated, this is an easy one to miss and code incorrectly.
Osteomyelitis picks up 24 new codes for “Other osteomyelitis” (M86.8X), extending site-specific reporting to the shoulder, upper arm, forearm, hand, thigh, lower leg, ankle, and foot, plus an “other site” option. Each site follows the familiar right/left/unspecified pattern. For example, under M86.8X1 (shoulder):
- M86.8X11 — Other osteomyelitis, right shoulder
- M86.8X12 — Other osteomyelitis, left shoulder
- M86.8X19 — Other osteomyelitis, unspecified shoulder
The same three-code pattern repeats for each of the other listed sites.
Chapter 9: Diseases of the Circulatory System (I00–I99)
Inherited arrhythmia conditions are finally getting codes of their own instead of being lumped into a catch-all category. New additions include:
- I47.22 — Catecholaminergic polymorphic ventricular tachycardia
- I49.81 — Brugada syndrome
- I49.82 — Ventricular bigeminy
For I49.82 specifically, coders are instructed to use an additional code, when applicable, to capture associated symptoms such as dizziness (R42) or syncope (R55).
Before this update, all three conditions were being coded under I49.8 (Other specified cardiac arrhythmias). Those references are being deleted from I49.8, and a new residual code is being created to absorb what’s left:
I49.89 — Other specified cardiac arrhythmias not elsewhere classified, which now covers coronary sinus rhythm disorder, ectopic rhythm disorder, and nodal rhythm disorder.
Practically, this means any encoder logic or superbill built around I49.8 for these three conditions needs to be updated, or claims will map to the wrong code starting October 1.
Chapter 15: Pregnancy, Childbirth, and the Puerperium (O00–O9A)
This chapter carries 23 new codes, almost entirely focused on ectopic pregnancy diagnoses — eight for tubal pregnancy and fifteen covering other ectopic locations.
Interstitial ectopic pregnancy — implantation in the most proximal portion of the fallopian tube — is a rare but high-risk subtype associated with elevated maternal mortality and a high rupture risk, largely because it’s difficult to diagnose early. Two new category headings are added and each will be broken out by laterality (right, left, unspecified):
- O00.12 — Interstitial ectopic pregnancy without intrauterine pregnancy
- O00.13 — Interstitial ectopic pregnancy with intrauterine pregnancy
Beyond the interstitial subtype, additional ectopic pregnancy codes are being organized by anatomic site — cesarean scar (O00.3), cervical (O00.4), cornual (O00.5), and other (O00.8) — with each site further split by whether an intrauterine pregnancy is also present. Coders working obstetric charts should review the full pregnancy chapter coding guidelines alongside these additions, since sequencing and combination coding rules apply.
A single new category addresses vanishing twin syndrome (VTS) — the spontaneous, partial or complete reabsorption of one twin, typically during the first trimester. VTS occurs in roughly 15–35% of twin pregnancies, and while its cause isn’t fully understood, risk factors include a higher number of transferred embryos in IVF pregnancies, an elevated initial gestational sac count, and advanced maternal age. The new codes are:
- O31.4 — Continuing pregnancy after vanishing twin syndrome of one fetus or more
- O31.40 — …unspecified trimester
- O31.41 — …first trimester
- O31.42 — …second trimester
- O31.43 — …third trimester
Finally, four subcategories under “Maternal care for (suspected) chromosomal abnormality in fetus” are getting expanded notes (not new codes) to reflect specific genetic syndromes now identifiable through prenatal testing:
- O35.11 — adds Patau syndrome (Trisomy 13)
- O35.12 — adds Edwards syndrome (Trisomy 18)
- O35.13 — adds Down syndrome (Trisomy 21)
- O35.15 — adds Klinefelter syndrome, Trisomy X, and XYY syndrome (sex chromosome abnormalities)
Since these are note-only changes, no new code numbers are involved, but coders should also update any internal documentation or cheat sheets that reference these categories.
Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00–T88)
This chapter sees 25 additions and 5 deletions concentrated in toxic effects coding. New base codes, each with four child codes for accidental (unintentional), intentional self-harm, assault, and undetermined intent, include:
- T52.81 — Toxic effects of alkenes
- T52.82 — Toxic effects of cycloparaffins
- T52.89 — Toxic effects of other organic solvents
- T59.82 — Toxic effects of hexamethylene diisocyanate
- T65.85 — Toxic effect of medetomidine
The existing code T52.8X (Toxic effects of organic solvents) and its four child codes are being retired to make room for this more granular breakdown.
It’s worth reinforcing the distinction between poisoning and toxic effects here, since the two are frequently confused: poisoning refers to harm from the improper use of a substance, while a toxic effect refers to harm from exposure to a substance regardless of intended use. This distinction directly affects code selection, so it’s a good candidate for a coder refresher — see this guide on poisoning, adverse effects, toxic effects, and underdosing for a fuller comparison.
Cycloparaffin exposure deserves a clinical note, since the substance itself may not be familiar to every coder. Cycloparaffins (naphthenes and cycloalkanes) are hydrocarbon solvents found in crude oil, adhesives, sealants, and jet propellant fuel. Prolonged exposure through inhalation, ingestion, or skin contact has been linked to central nervous system effects (headache, fatigue, dizziness, difficulty concentrating), gastrointestinal symptoms from ingestion (abdominal pain, nausea, vomiting), and skin irritation from direct contact.
Chapter 21: Factors Influencing Health Status and Contact with Health Services (Z00–Z99)
New child codes under Z77.3 (Contact with and suspected exposure to war theater) will let coders capture specific toxic exposures tied to military service:
- Z77.32 — Contact with and (suspected) exposure to burn pits in war theater
- Z77.33 — Contact with and (suspected) exposure to Agent Orange
Because Agent Orange now has its own dedicated code, the existing reference to it under Z77.39 (Contact with and suspected exposure to other war theater) is being deleted.
Agent Orange exposure are well-documented and serious health legacy for Vietnam-era veterans. It was a herbicide mixture combining 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid, and its manufacturing produced the toxic byproduct 2,3,7,8-tetrachlorodibenzo-p-dioxin — classified by the IARC as a Group 1 human carcinogen capable of binding hormone receptors and altering DNA. Exposure has been associated with increased risk of prostate cancer, bladder cancer, dementia, soft-tissue sarcomas, non-Hodgkin lymphoma, and lung cancer, as well as certain birth defects in the children of veterans who served in Vietnam and Korea.
These new codes exist largely to support implementation of the PACT Act of 2022 (Promise to Address Comprehensive Toxins), which expanded benefits for veterans exposed to burn pits and other toxic substances. Accurate coding here isn’t just an administrative detail — it feeds the data used to connect exposure history to diagnoses and encourages veteran participation in Agent Orange Registry Health Exams.
What Coders Should Do Before October 1
Given the volume of Excludes note and Code Also revisions layered on top of the code changes themselves, don’t rely on memory or last year’s cheat sheets. A few practical steps:
- Confirm your encoder or EHR code tables are updated with the FY 2027 code set before the October 1 effective date.
- Pay close attention to Excludes1 revisions, like the M72.8 change above — these silently redirect correct coding without adding a new code to notice.
- Review the difference between poisoning and toxic effects if your practice handles substance-exposure cases; understanding Excludes1 vs. Excludes2 notes will help you apply the toxic-effects revisions correctly.
- If you code obstetric charts, walk through the new ectopic pregnancy and vanishing twin syndrome codes against actual documentation examples before it goes into effect, since these carry sequencing implications.
Most electronic encoders will flag new and deleted codes automatically, but the notes, symbols, and instructional changes are easy to scroll past. Take the time to read through them chapter by chapter — that’s usually where denials and audit findings originate, not from missing a brand-new code outright.
