Crystal's Coder Hub🧬 ICD-10 CM B47.9 — Mycetoma, Unspecified
Billable Code Confirmed
[ICD-10 CM] B47.9 is a valid, billable 4-character ICD-10-CM diagnosis code for FY2026. Characters 1-3 (
B47) define the category (Mycetoma); the 4th character (.9) specifies “unspecified” type when the causative organism class has not been identified or documented. No additional characters are required or available.
Non-Billable Parent Codes — Never Submit These
- ❌
B47— 3-character header — does not specify organism type (fungal vs. bacterial); not valid for claim submissionAlways submit B47.9 (all 4 characters) when mycetoma is documented without specification of the causative organism type.
Clinical Context: Unspecified Organism Type Drives This Code
ICD-10-CM B47.9 captures mycetoma when the provider has NOT documented or identified whether the causative agent is a fungus (which would require B47.0 — Eumycetoma) or a filamentous bacterium/actinomycete (which would require B47.1 — Actinomycetoma). CDI query is appropriate when workup results (culture, histopathology) are available but organism class is not reflected in provider documentation.
Code Classification
ICD-10-CM Diagnosis Code — wRVU, assistant-at-surgery payable status, and global period fields are not applicable to diagnosis codes. For associated inpatient procedures, refer to the ICD-10-PCS Crosswalk section below. For outpatient and profee procedure billing, refer to the Commonly Associated CPT Codes section.
🔍 Code Description
ICD-10 CM B47.9 classifies Mycetoma, unspecified — a chronic, progressive granulomatous infection of the skin, subcutaneous tissue, and potentially underlying bone, caused by either fungi or filamentous bacteria, when the specific organism class has not been identified or documented. The “unspecified” designation signals a documentation gap that should trigger a CDI query when laboratory or pathology results are available.
Mycetoma is characterized by a classic clinical triad: localized swelling, sinus tract formation, and discharge containing granules (which represent colonies of the causative organism). The feet and lower extremities are most commonly affected, often following traumatic inoculation through the skin — classically from thorns or splinters in individuals who walk barefoot. The condition can progress to involve deep fascia and bone, causing significant tissue destruction if untreated.
🌳 Code Tree / Hierarchy
B47 Mycetoma ❌ Non-billable (3-character header)
│
├── B47.0 Eumycetoma ✅ Billable (fungal mycetoma — caused by true fungi, e.g., Madurella mycetomatis)
├── B47.1 Actinomycetoma ✅ Billable (bacterial mycetoma — caused by filamentous bacteria, e.g., Nocardia, Actinomadura)
└── B47.9 Mycetoma, unspecified ◀ THIS CODE ✅ Billable (organism class not documented)
Always Query for Organism Type
If culture, biopsy, or histopathology results identify the organism as fungal or bacterial, query the provider to update documentation — B47.0 and B47.1 are more specific codes and may carry different treatment and clinical resource implications than B47.9.
✅ Includes
The following clinical terms and scenarios map to B47.9 when documented:
- Madura foot NOS (per ICD-10-CM Includes note)
- Maduromycosis, unspecified
- Mycetoma when organism type (fungal vs. bacterial) is not specified or documented
- Mycetoma foot / Madura foot when culture or histopathology results are pending or unavailable
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with B47.9
| Code | Description | Note |
|---|---|---|
| No Excludes 1 | No Excludes 1 notes apply at the B47 or B47.9 level | N/A |
Excludes 1 Violation Risk
There are no formal Excludes 1 notes at this code level; however, do NOT code B47.9 simultaneously with B47.0 or B47.1. Once the organism is identified as fungal or bacterial, only the specific code should be reported — not both.
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| No Excludes 2 | No formal Excludes 2 notes apply at the B47.9 level | Additional codes for manifestations (e.g., osteomyelitis) should be reported when documented and supported |
📋 Clinical Overview
Eumycetoma vs. Actinomycetoma vs. Unspecified
Accurate code selection depends entirely on whether the causative organism class has been identified. The table below highlights the key clinical and coding differences to guide CDI queries and code assignment.
| Feature | B47.0 — Eumycetoma | B47.1 — Actinomycetoma | B47.9 — Unspecified |
|---|---|---|---|
| Causative Organism | True fungi (e.g., Madurella mycetomatis, Scedosporium) | Filamentous bacteria (e.g., Nocardia brasiliensis, Actinomadura madurae) | Not identified or documented |
| Granule Color | Black or white (large, firm) | White, yellow, or red (small, soft) | Unknown |
| Treatment | Antifungal agents ± surgery | Prolonged antibacterial therapy (sulfonamides, TMP-SMX, aminoglycosides) | Empiric until organism identified |
| Prognosis | Poorer; more resistant to treatment | Better response to medical therapy | Indeterminate |
| Code to Use | B47.0 | B47.1 | B47.9 (only when unspecified) |
CDI Query Trigger — Organism Class Documentation
When the H&P, culture report, or pathology report identifies the organism as fungal or bacterial, but the provider’s assessment/plan simply states “mycetoma” without specifying the type, send a CDI query asking the provider to clarify: “Is the mycetoma documented in this encounter of fungal (eumycetoma) or bacterial/actinomycetes (actinomycetoma) etiology per available culture/histopathology results?”
Manifestations & Symptom Burden
Mycetoma may be accompanied by significant local and systemic manifestations that should be coded additionally when documented:
- Secondary bacterial superinfection: Sinus tracts are open wounds susceptible to superinfection; code the bacterial organism separately if identified
- osteomyelitis |Osteomyelitis: Bone involvement is a known complication of advanced mycetoma; code M86.9 (Osteomyelitis, unspecified) or a more specific osteomyelitis code if documented
- lymphadenopathy |Lymphadenopathy: Regional lymph node involvement may be coded with R59.1 (Generalized enlarged lymph nodes) if documented
Coding Manifestations
Always code documented manifestations to fully capture patient complexity.
Examples include:
- M86.172 — Other acute osteomyelitis, left ankle and foot (if osteomyelitis is documented and confirmed)
- L08.9 — Local infection of skin and subcutaneous tissue, unspecified (for secondary skin infection)
- Z77.121 — Contact with and exposure to soil and dust (applicable historical/exposure Z-code)
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024-2025 Implementation) |
| HCC Assignment | ❌ Not HCC-Mapped |
| HCC Category | N/A |
| RAF Coefficient | N/A |
B47.9 does not map to an HCC under CMS-HCC v28 and does not contribute to the patient’s RAF score.
Capture Annually
Because B47.9 is not HCC-mapped, there is no annual risk-adjustment capture requirement for this code. However, thorough documentation of the organism type (fungal vs. bacterial), extent of involvement (skin, subcutaneous, bone), and any comorbidities is still essential for accurate DRG grouping and clinical documentation integrity.
🏥 MS-DRG Assignment
MDC 18 — Infectious and Parasitic Diseases (Systemic or Unspecified Sites)
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 868 | Other Infectious and Parasitic Diseases Diagnoses with MCC | ~2.80 - 3.20 |
| DRG 869 | Other Infectious and Parasitic Diseases Diagnoses with CC | ~1.50 - 1.80 |
| DRG 870 | Other Infectious and Parasitic Diseases Diagnoses without CC/MCC | ~0.90 - 1.10 |
Approximate. Verify against IPPS FY2026 Final Rule tables.
Sequencing and Complications
When B47.9 is the principal diagnosis (reason for admission after study), it groups to MDC 18 → DRG 868/869/870. The DRG tier is determined by secondary diagnoses functioning as MCC or CC. When mycetoma is sequenced as a secondary diagnosis — for example, if a patient was admitted primarily for osteomyelitis — B47.9 may function as a CC, improving the DRG weight of the principal diagnosis grouper. Always confirm B47.9’s CC/MCC status against the FY2026 CMS CC/MCC Exclusion Table for the given principal diagnosis.
🔗 Related ICD-10-CM Codes
Organism-Type Variants — B47 Category
| Code | Description |
|---|---|
| B47.9 | Mycetoma, unspecified ← This Code |
| B47.0 | Eumycetoma — fungal mycetoma |
| B47.1 | Actinomycetoma — bacterial/actinomycetes mycetoma |
Related Fungal and Subcutaneous Infection Codes
| Code | Description |
|---|---|
| B35.6 | Tinea pedis (superficial fungal foot infection — NOT mycetoma) |
| B44.1 | Other pulmonary aspergillosis |
| B48.8 | Other specified mycoses |
| M86.9 | Osteomyelitis, unspecified (sequelae of advanced mycetoma) |
| L08.9 | Local infection of skin and subcutaneous tissue, unspecified |
🛠️ Commonly Associated CPT Codes (Infectious Disease / Surgery)
Outpatient and Profee Setting Context
In the outpatient/profee setting, B47.9 most commonly pairs with surgical debridement, wound culture, and fungal/bacterial diagnostic procedures. Modifier -26 applies to the professional component when the facility is billing globally for imaging or lab interpretations.
| CPT Code | Description | Profee Coding Notes |
|---|---|---|
| 11042 | Debridement, subcutaneous tissue; first 20 sq cm | Pair with B47.9; add Modifier -25 to E/M if performed same day |
| 11043 | Debridement, muscle and/or fascia; first 20 sq cm | Use when fascia is involved; supports higher acuity |
| 87102 | Culture, fungal, not blood; other source | Order when eumycetoma suspected; supports B47.0 specificity |
| 87070 | Culture, bacterial, any source except urine/blood | Order when actinomycetoma suspected; supports B47.1 specificity |
| 87220 | Tissue examination for fungi (KOH preparation) | Rapid in-office test to differentiate fungal etiology |
| 11100 | Biopsy of skin; single lesion | Histopathology to confirm granule type and organism class |
NCCI Bundling Considerations
- Debridement (11042) billed on the same day as an E/M service requires Modifier -25 on the E/M to demonstrate that the evaluation was separate and significant from the decision to debride.
- Fungal culture (87102) and bacterial culture (87070) are not typically bundled with each other and may both be reported when dual organism workup is ordered, provided medical necessity is documented.
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
When B47.9 is an inpatient diagnosis, these PCS codes are relevant for associated inpatient procedures.
| PCS Section | Body System | Root Operation | Clinical Application |
|---|---|---|---|
| 0 (Medical and Surgical) | J (Subcutaneous Tissue and Fascia) | B (Excision) | Surgical excision of mycetoma lesion from foot/lower extremity — e.g., 0JBM0ZZ (right foot, open) or 0JBN0ZZ (left foot, open) |
| 0 (Medical and Surgical) | J (Subcutaneous Tissue and Fascia) | 9 (Drainage) | Drainage of sinus tracts — e.g., 0J9M0ZZ (right foot, open, no device) |
| 3 (Administration) | E (Physiological Systems and Anatomical Regions) | 0 (Introduction) | IV antifungal or antimicrobial administration — e.g., 3E033GC (peripheral vein, percutaneous, other therapeutic substance) |
💊 Coding Scenarios and Examples
Scenario 1 — Outpatient/Profee: Established Patient with Mycetoma, Organism Pending
Clinical Vignette: A 38-year-old male originally from sub-Saharan Africa presents to an infectious disease clinic with a 6-month history of painless swelling of the right foot with sinus tract formation and dark granule discharge. Cultures are pending. Provider documents assessment as “mycetoma, type to be determined pending culture results.”
CPT / HCPCS (Profee):
- 99214 — Office visit, established patient, moderate complexity (E/M supporting evaluation and ordering of workup)
- 87102 — Fungal culture, not blood (ordered for organism identification)
- 87070 — Bacterial culture (ordered for organism identification)
ICD-10-CM:
- B47.9 — Mycetoma, unspecified (organism class not yet documented — appropriate use of unspecified code while culture is pending)
Scenario 2 — Inpatient: Admission for Mycetoma with Osteomyelitis
Clinical Vignette: A 45-year-old female immigrant is admitted for surgical debridement of a chronic mycetoma of the left foot with imaging-confirmed osteomyelitis of the left calcaneus. The organism type remains undocumented in the H&P and assessment. The patient undergoes open excision of the subcutaneous lesion and drainage of sinus tracts.
Principal Diagnosis:
- B47.9 — Mycetoma, unspecified (reason for admission — chronic progressive infection)
Secondary Diagnoses:
- M86.172 — Other acute osteomyelitis, left ankle and foot (documented complication — functions as CC or MCC; verify in FY2026 CC/MCC table)
- Z87.39 — Personal history of other musculoskeletal disorders (if applicable)
MS-DRG Assignment: B47.9 as principal → MDC 18. With osteomyelitis as a CC/MCC secondary diagnosis, this case likely groups to DRG 868 (with MCC) or DRG 869 (with CC) depending on the osteomyelitis CC/MCC tier — verify with FY2026 grouper.
Scenario 3 — CDI Query: Vague Documentation of “Foot Infection — Madura Foot”
Clinical Vignette: Provider documents “Madura foot” in the assessment of an inpatient case. Culture results in the chart identify the organism as Actinomadura madurae, a filamentous bacterium. No further specificity is provided in the provider’s documentation regarding organism class.
Action / Outcome: The coder recognizes that “Madura foot NOS” maps to B47.9, but culture results support B47.1 (Actinomycetoma). A CDI query is appropriate: “The culture result dated [DATE] identifies Actinomadura madurae, a filamentous bacterium consistent with actinomycetoma. Can you please confirm and document whether the mycetoma in this encounter is of bacterial/actinomycetes etiology (actinomycetoma)?”
Query Response: Provider updates documentation to confirm: “Actinomycetoma — confirmed by culture, Actinomadura madurae.”
Corrected ICD-10-CM Coding:
- B47.1 — Actinomycetoma (more specific — supported by culture; replaces B47.9)
- M86.172 — Osteomyelitis, left ankle and foot (if bone involvement documented)
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Do Not Default to B47.9 When Organism is Identified. If culture, biopsy, or histopathology results in the record identify the organism as fungal or bacterial, query the provider to specify type — B47.9 is for truly unspecified cases only, not cases where the coder simply did not review the results. |
| ❌ | Do Not Confuse Mycetoma with Superficial Tinea Pedis. Tinea pedis (B35.6) is a superficial dermatophyte infection; mycetoma (B47.x) is a deep subcutaneous/bony infection with sinus tracts and granules. These are clinically and anatomically distinct — never interchange them. |
| ❌ | Do Not Omit Osteomyelitis Code When Bone Involvement is Documented. Advanced mycetoma frequently involves underlying bone; failure to code a separately documented osteomyelitis omits a legitimate CC/MCC and underrepresents patient complexity. |
| ✅ | Query for Organism Type When Lab Results are Available. When fungal or bacterial culture results appear in the chart but provider documentation is vague, send a CDI query to move from B47.9 to B47.0 or B47.1 — more specific codes better reflect clinical complexity. |
| ✅ | Verify B47.9 CC/MCC Status Against FY2026 Tables. When sequenced as a secondary diagnosis, B47.9 may function as a CC. Always cross-reference the FY2026 CMS IPPS CC/MCC Exclusion List against the principal diagnosis before finalizing DRG assignment. |
| ✅ | Code All Documented Manifestations. Sinus tracts, secondary infections, osteomyelitis, and lymphadenopathy are separately coded when documented and supported — each adds to the clinical picture and may affect DRG weight. |
📚 Sources
- CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. 1
- World Health Organization. Mycetoma Fact Sheet. WHO Media Centre. 2
- Fahal, A.H. (2004). Mycetoma: A Thorn in the Flesh. Transactions of the Royal Society of Tropical Medicine and Hygiene, 98(1), 3-11. (Source for clinical triad, granule characteristics, and endemic region data.) 3
- CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings. 4
- CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 18 — Infectious and Parasitic Diseases logic tables. 5
- AAPC Codify. ICD-10-CM Code B47.9 — Mycetoma, unspecified. Codify by AAPC, 2026. 6