K05.20 ICD-10-CM Code: Aggressive periodontitis, unspecified

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for K05.20 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on K05.20 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for K05.20

MedCoder structured workflow — derived from this code’s own official record

Before you code K05.20

1. Unspecified does not mean incorrect. When the record gives no greater specificity, K05.20 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

   ReviewK05.21, K05.22

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with K05.20. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

   See the official tabular notes

Choose the right path

1. Does the record document the detail a more specific sibling code needs?
   Yes → Review the specific siblings in this subcategory.
   No → Continue — K05.20 is appropriate when the documentation goes no further.

   ReviewK05.21, K05.22

2. Does the documentation support a condition named in K05.20’s Excludes1 note?
   Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
   No → Continue.

   ReviewK04.4, K04.7, K04.6

Consider K05.20. Then work the Use Additional Code note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

The conditions the Use Additional Code note names

Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

• Excludes1 — check before selecting K05.20(3 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with K05.20: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareK04.4, K04.7, K04.6

  See the official tabular notes · Guidelines I.A.12.a

• Use Additional Code — after identifying K05.20(8 notes)

  Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with K05.20 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

  ReviewF10, Z77.22, P96.81, Z87.891, Z57.31, F17

  See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed Clinical Terms (8)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic), gingival, aggressive
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic), gum, aggressive
• Infection, infected, infective (opportunistic), peridental, periodontal
• Infection, infected, infective (opportunistic), tooth, teeth, peridental, periodontal
• Pericementitis (chronic) (suppurative), acute
• Periodontitis (chronic) (complex) (compound) (local) (simplex), acute
• Periodontitis (chronic) (complex) (compound) (local) (simplex), aggressive
• Suppuration, suppurative, gum

Official Coding Guidelines

No excerpt in the ICD-10-CM Official Guidelines names this code specifically. Its chapter carries only this chapter-wide note:

Don’t confuse K05.20 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of K05.20 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• K04.4— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of acute apical periodontitis moves the case to K04.4; the two are not reported together unless documented as unrelated.

  Full comparison: K05.20 vs K04.4 →

• K04.7— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of periapical abscess moves the case to K04.7; the two are not reported together unless documented as unrelated.

  Full comparison: K05.20 vs K04.7 →

• K04.6— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of periapical abscess with sinus moves the case to K04.6; the two are not reported together unless documented as unrelated.

  Full comparison: K05.20 vs K04.6 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name K05.20 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: K04.4 — Acute apical periodontitis of pulpal origin (via K05.2.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Excludes2 note: K13 — Other diseases of lip and oral mucosa (via K05.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 6 MS-DRGs: DRG 011 (MDC PRE), DRG 012 (MDC PRE), DRG 013 (MDC PRE), DRG 157 (MDC 03), DRG 158 (MDC 03), DRG 159 (MDC 03).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):DIG002 — Disorders of teeth and gingiva (default); DEN001 — Any dental condition including traumatic injury; DEN002 — Nontraumatic dental conditions; DEN003 — Caries, periodontitis, and other preventable dental conditions.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Disorders of teeth and gingiva, Any dental condition including traumatic injury, Nontraumatic dental conditions, Caries, periodontitis, and other preventable dental conditions).

K04.5 — Chronic apical periodontitis, K04.6 — Periapical abscess with sinus, K04.7 — Periapical abscess without sinus, K04.8 — Radicular cyst, K04.90 — Unspecified diseases of pulp and periapical tissues, K04.99 — Other diseases of pulp and periapical tissues, K05.00 — Acute gingivitis, plaque induced, K05.01 — Acute gingivitis, non-plaque induced, K05.10 — Chronic gingivitis, plaque induced, K05.11 — Chronic gingivitis, non-plaque induced, K05.21 — Aggressive periodontitis, localized, K05.211 — Aggressive periodontitis, localized, slight, K05.212 — Aggressive periodontitis, localized, moderate, K05.213 — Aggressive periodontitis, localized, severe, K05.219 — Aggressive periodontitis, localized, unspecified severity, K05.22 — Aggressive periodontitis, generalized, K05.221 — Aggressive periodontitis, generalized, slight, K05.222 — Aggressive periodontitis, generalized, moderate, K05.223 — Aggressive periodontitis, generalized, severe, K05.229 — Aggressive periodontitis, generalized, unspecified severity, +613 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Abscess”, “Periodontitis”; these codes share that main term but sit in a different category of the Tabular List.

J85.3 — Abscess of mediastinum (mediastinum), J86.0 — Pyothorax with fistula (chest, with fistula), J86.9 — Pyothorax without fistula (chest), J98.09 — Other diseases of bronchus, not elsewhere classified (bronchi), K04.01 — Reversible pulpitis (pulp, pulpal), K04.02 — Irreversible pulpitis (pulp, pulpal, irreversible), K04.4 — Acute apical periodontitis of pulpal origin (apical, acute), K04.5 — Chronic apical periodontitis (apical), K04.6 — Periapical abscess with sinus (apical, with sinus), K04.7 — Periapical abscess without sinus (dental), K11.3 — Abscess of salivary gland (parotid), K12.2 — Cellulitis and abscess of mouth (mouth), K13.0 — Diseases of lips (lip), K14.0 — Glossitis (tongue), K20.80 — Other esophagitis without bleeding (esophagus), K35.33 — Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess (cecum), K57.00 — Diverticulitis of small intestine with perforation and abscess without bleeding (with, diverticular disease, small intestine), K57.01 — Diverticulitis of small intestine with perforation and abscess with bleeding (with, diverticular disease, small intestine, with, bleeding), K57.20 — Diverticulitis of large intestine with perforation and abscess without bleeding (with, diverticular disease, large intestine), K57.21 — Diverticulitis of large intestine with perforation and abscess with bleeding (with, diverticular disease, large intestine, with, bleeding), +158 more

Contextual Map

Every relationship of K05.20 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run K05.20 with these 2 related codes in Claim Check

Hierarchy

• K00-K95 — Chapter 11: Diseases of the Digestive System (K00-K95) (K00-K95)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• K04.4 — Acute apical periodontitis of pulpal origin[Excludes1](via K05.2.-): “acute periodontitis (K05.2-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes

• K13 — Other diseases of lip and oral mucosa[Excludes2](via K05.-): “certain disorders of gingiva and edentulous alveolar ridge (K05-K06)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• DIG002 — Disorders of teeth and gingiva[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)
• DEN001 — Any dental condition including traumatic injury[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)
• DEN002 — Nontraumatic dental conditions[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)
• DEN003 — Caries, periodontitis, and other preventable dental conditions[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• DRG 011 — TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITH MCC[MS-DRG]: “TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITH MCC (MDC PRE)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 012 — TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITH CC[MS-DRG]: “TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITH CC (MDC PRE)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 013 — TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITHOUT CC/MCC[MS-DRG]: “TRACHEOSTOMY FOR FACE, MOUTH AND NECK DIAGNOSES OR LARYNGECTOMY WITHOUT CC/MCC (MDC PRE)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 157 — DENTAL AND ORAL DISEASES WITH MCC[MS-DRG]: “DENTAL AND ORAL DISEASES WITH MCC (MDC 03)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 158 — DENTAL AND ORAL DISEASES WITH CC[MS-DRG]: “DENTAL AND ORAL DISEASES WITH CC (MDC 03)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 159 — DENTAL AND ORAL DISEASES WITHOUT CC/MCC[MS-DRG]: “DENTAL AND ORAL DISEASES WITHOUT CC/MCC (MDC 03)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• Pre-MDC[MDC crossing]: “Pre-MDC — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 153 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
• MDC 03 — Diseases and Disorders of the Ear, Nose, Mouth and Throat[MDC crossing]: “Diseases and Disorders of the Ear, Nose, Mouth and Throat — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,147 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic), gingival, aggressive[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic), gum, aggressive[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Infection, infected, infective (opportunistic), peridental, periodontal[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Infection, infected, infective (opportunistic), tooth, teeth, peridental, periodontal[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Pericementitis (chronic) (suppurative), acute[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Periodontitis (chronic) (complex) (compound) (local) (simplex), acute[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Periodontitis (chronic) (complex) (compound) (local) (simplex), aggressive[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Suppuration, suppurative, gum[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (33)

• K05 — Gingivitis and periodontal diseases[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.0 — Acute gingivitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.00 — Acute gingivitis, plaque induced[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.01 — Acute gingivitis, non-plaque induced[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.1 — Chronic gingivitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.10 — Chronic gingivitis, plaque induced[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.11 — Chronic gingivitis, non-plaque induced[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K05.2 — Aggressive periodontitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 25 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to K05.20 in its code family, with their registry titles.

• K05.01 — Acute gingivitis, non-plaque induced
• K05.1 — Chronic gingivitis
• K05.10 — Chronic gingivitis, plaque induced
• K05.11 — Chronic gingivitis, non-plaque induced
• K05.2 — Aggressive periodontitis
• K05.21 — Aggressive periodontitis, localized
• K05.211 — Aggressive periodontitis, localized, slight
• K05.212 — Aggressive periodontitis, localized, moderate
• K05.213 — Aggressive periodontitis, localized, severe
• K05.219 — Aggressive periodontitis, localized, unspecified severity

View all codes in the K05 family