Every October, a new fiscal year brings a new ICD-10-CM code set, and FY 2027 is no exception. The Centers for Medicare & Medicaid Services (CMS) released the updated code set in June 2026, and the changes take effect October 1, 2026, applying to discharges and patient encounters through September 30, 2027.
This year's ICD-10-CM code update adds 190 new codes, deletes 30, and revises four, which spans 33 clinical topics across nearly every chapter of the code book. While that's a modest volume compared to some past years, several of the additions reflect meaningful shifts in clinical documentation and specificity that medical coders, clinical documentation integrity (CDI) specialists, and revenue cycle teams should build into their FY 2027 preparation now.
The Big-Ticket Items: Two Categories Drive Nearly a Quarter of All New Codes
Two new subcategories account for a large share of this year’s additions. The first is category O31.4, continuing pregnancy after vanishing twin syndrome of one fetus or more, which alone contributes 33 new codes structured by trimester and encounter type. Vanishing twin syndrome is the loss or resorption of one embryo in a multiple gestation. Previously, there was not a dedicated way to document a continuing pregnancy after this occurs; the new subcategory closes that gap with greater specificity for maternal-fetal medicine documentation.
The second is T52.82, toxic effect of cycloparaffins, which adds 12 new codes. It is part of a broader expansion of the toxic effects section: T52.81, toxic effect of alkenes, adds 12 codes of its own, and new codes also cover toxic effects of hexamethylene diisocyanate (HDI) and medetomidine. The medetomidine codes are worth flagging in particular. Medetomidine is a veterinary sedative that has increasingly turned up as an adulterant in illicit fentanyl supplies, and the new codes are intended to support overdose surveillance and public health tracking.
Greater Specificity in Oncology and Blood Disorders
Secondary malignancy coding gets more precise this year. New codes C78.31, secondary malignant neoplasm of larynx; C78.32, secondary malignant neoplasm of pharynx; and C79.83, secondary malignant neoplasm of oral cavity, let coders pinpoint metastatic sites that previously had to be reported with the nonspecific C78.39 or C79.89. The Neoplasm Table has been updated accordingly. Separately, the D05.- carcinoma in situ of breast codes can no longer be reported together with a C50.- malignant neoplasm of breast code for the same patient. This change will require coders to look more closely at documentation when both diagnoses appear in a chart.
In blood disorders, subcategory D69.1, qualitative platelet defects, has been split into two more specific codes: D69.11 for Glanzmann thrombasthenia, a rare autosomal recessive platelet function disorder, and D69.19 for other qualitative defects such as Bernard-Soulier syndrome, grey platelet syndrome, and thrombocytopathy. This gives clinical and research teams a way to track Glanzmann thrombasthenia distinctly rather than grouping it with other platelet conditions.
Cardiac Medical Coding Gets More Granular
The circulatory chapter picks up several new codes aimed at genetic and arrhythmic conditions. Dilated cardiomyopathy (I42.0) expands into I42.00, unspecified; I42.01, familial-genetic; and I42.09, other, reflecting the clinical importance of documenting whether a DCM diagnosis has a known genetic or familial cause. New codes also capture arrhythmogenic cardiomyopathy (ARVC/ARVCD), catecholaminergic polymorphic ventricular tachycardia (CPVT), Brugada syndrome, and ventricular bigeminy. Previously, these conditions had to be reported with less specific codes or none at all.
New Codes for Dental-Related Sinusitis, Pelvic Disease, and Foot Conditions
A new subcategory, J34.83-, odontogenic sinusitis, lets coders identify bacterial sinusitis that originates from a dental infection or procedure, with a sixth character specifying which sinus is involved: maxillary, ethmoid, frontal, or sphenoid. A related respiratory addition, J4B, covers pulmonary mycetoma, which is a fungal “ball” in the lung. There is also a code note with J4B that points to adding any relevant coccidioidomycosis and aspergillosis codes.
The digestive and genitourinary chapters add K6A, diseases of the pelvis, not elsewhere classified, including new codes that separate prevesical, or retropubic, abscess from other pelvic abscesses. K31.B, hypertrophic pyloric stenosis in childhood, gives pediatric coders a dedicated code for a condition previously reported with a less specific, largely adult-oriented code. And K74.0A now distinguishes stage F2 hepatic fibrosis from stage F1, a distinction that matters clinically because mortality risk increases starting at stage 2.
Musculoskeletal coders will want to note that plantar fasciitis and plantar fascial fibromatosis, also known as Ledderhose disease, were previously reported with the same shared code, M72.2. These conditions are now differentiated, with new subcategory M67.A- for plantar fasciitis by foot and laterality. The M86.8X- osteomyelitis codes also expand by site and laterality, which will be relevant for documenting Pott’s puffy tumor, or frontal bone osteomyelitis with subperiosteal abscess.
Genetic Syndromes Get Their Own Codes
Several rare and genetic conditions move from “code as a symptom” to dedicated codes this year. VEXAS syndrome, an acquired autoinflammatory disease caused by somatic UBA1 mutations, gets a new M04 subcategory code. Loeys-Dietz syndrome, a multisystem aortopathy distinct from Marfan syndrome, gets a specific code under Q87. Lynch syndrome, along with other hereditary cancer syndromes such as BRCA1/BRCA2 and Li-Fraumeni syndrome, gets a new category so inherited cancer risk can be documented explicitly rather than folded into a general family-history code.
Other Notable Additions
A handful of smaller but clinically useful changes round out the update. Post-bariatric hypoglycemia, which is recurrent, postprandial low blood sugar that can develop months after bariatric surgery, will get two new codes under E89.83. Adult BMI codes under Z68.1 are split to add more granularity at the low end of the range, aligning with underweight and malnutrition thresholds. Gender identity disorder “in remission” gets its own code, alongside new Z codes for personal history of social, medical, and surgical gender transition, as well as personal history of gender detransition. On the exposure side, new Z77 codes capture exposure to burn pit emissions and Agent Orange in war theaters and to blast overpressure.
What’s Being Deleted
The FY 2027 update removes 30 codes, most notably the S23.420 series for sternoclavicular sprain, including the base code plus its initial encounter, subsequent encounter, and sequela variants. Facilities still coding these injuries under the old codes will need to identify the replacement documentation pathway before October 1.
Getting Ready for October 1
As with every annual ICD-10-CM update, the changes cluster around a few themes: more precise anatomical specificity for cancer and infection sites, dedicated codes for genetic and rare-disease diagnoses that used to require workarounds, and expanded surveillance codes for emerging public health concerns like illicit substance adulterants and environmental exposures.
None of this requires a wholesale overhaul of coding workflows, but CDI teams, coders, and providers documenting in affected specialties, especially maternal-fetal medicine, oncology, cardiology, and toxicology, should review the new code descriptors and inclusion terms before the October 1, 2026, effective date. For revenue cycle leaders, the priority is making sure coding teams, CDI workflows, provider education, and audit processes are ready to support accurate documentation and reduce avoidable claim disruption.
The complete code files, including the addendum and conversion table, are available on the CMS website. The official ICD-10-CM Guidelines for Coding and Reporting should be reviewed as soon as possible. Contact us for support in preparing your medical coding and CDI teams for annual code updates or for more information about our medical coding services and clinical documentation integrity services.
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