Actinomycetoma is a chronic, localized, slowly progressive subcutaneous bacterial infection caused by aerobic actinomycetes — specifically genera including Nocardia, Actinomadura, Streptomyces, and Nocardiopsis — that infiltrates the skin, connective tissue, and in advanced cases, bone. It is the bacterial subtype of the broader category mycetoma, which also includes eumycetoma (the fungal form caused by true fungi such as Madurella mycetomatis); the key distinction is etiology — actinomycetoma is bacterial and typically responds to prolonged antibiotic therapy, whereas eumycetoma is fungal and requires antifungal agents or surgery. The pathological mechanism involves inoculation via minor trauma (thorn puncture, wood splinter), followed by deep-tissue granulomatous inflammation, formation of sulfur-like granules made of the causative organisms and host defense cells, and development of communicating sinus tracts that drain seropurulent exudate. The classic clinical triad is firm swelling (tumefaction), subcutaneous nodules with abscess formation, and draining sinuses containing granules; 80% of all mycetoma cases affect the foot (“Madura foot”), though the hand, leg, back, and head can also be involved. Clinically relevant subtypes are classified by granule color: pale/white grain (e.g., Nocardia brasiliensis; B47.1), red grain (Actinomadura pelletieri; B47.1), and yellow grain (Streptomyces somaliensis; B47.1) — all coded under the same ICD-10-CM code B47.1. This condition is commonly confused with eumycetoma (B47.0) — remember: actinomycetoma is bacterial (curable with antibiotics), eumycetoma is fungal (much harder to treat and more localized).
"fungus,” “mushroom” — combining form; historically applied because early observers mistakenly classified actinomycetes as fungi due to their filamentous, branching growth
Noun-forming suffix — “tumor, swelling, mass” or “condition resulting in a growth”
The term entered medical English in the late 1800s-early 1900s as actinomycetoma (noun), coined from New Latin/Greek components by early microbiologists following the work of Pinoy (1913), who formally distinguished actinomycetoma (bacterial) from eumycetoma (fungal). The root aktis (“ray”) connects actinomycetoma to the entire actino- root family: actinomycosis (actino- + myc- + -osis → ray-fungus condition), Actinomyces (ray fungus → genus name for the causative bacteria), and actinotherapy (ray + treatment → radiation-based therapy). The combining form ‑mycet- also appears in mycetoma (fungus + swelling), eumycetoma (true + fungus + swelling), and mycology (fungus + study of).
🔀 ALIASES / ALTERNATE TERMS
Actinomycotic(adjective form — e.g., “actinomycotic mycetoma,” “actinomycotic grain,” “actinomycotic sinuses”)
Actinomycotic mycetoma(clinical synonym; used interchangeably in dermatology and infectious disease settings; coded B47.1)
Bacterial mycetoma(lay/clinical synonym distinguishing it from the fungal form; used in tropical medicine contexts)
Madura foot (bacterial form)(historical lay term; originated from Madura, India where first described by Gill in 1842; only applies when the foot is the affected site; coded B47.1 when bacterial)
Mycetoma(parent/umbrella term encompassing both actinomycetoma and eumycetoma; unspecified form coded B47.9)
Eumycetoma(the fungal counterpart; caused by true fungi; coded B47.0; treated with antifungals vs. antibiotics for actinomycetoma)
White/pale grain actinomycetoma(etiologic subtype caused by Nocardia brasiliensis or Streptomyces somaliensis; granule color aids organism identification; coded B47.1)
Red grain actinomycetoma(etiologic subtype caused by Actinomadura pelletieri; red granules on gross exam; coded B47.1)
Nocardial mycetoma(organism-specific subtype caused by Nocardia brasiliensis, the most common isolate worldwide; coded B47.1)
🔗 RELATED TERMS
Eumycetoma — the fungal counterpart to actinomycetoma; caused by true fungi (e.g., Madurella mycetomatis); shares the same clinical triad but is more localized, harder to cure, and coded separately as B47.0
Mycetoma — the overarching clinical entity encompassing both actinomycetoma (bacterial) and eumycetoma (fungal); unspecified form coded B47.9; the grain color and microscopy determine which subtype
Actinomycosis — a related but distinct chronic bacterial infection caused by Actinomyces israelii (anaerobic); affects the oral/cervicofacial region, lungs, and GI tract — not the skin via trauma like actinomycetoma; coded under A42.xx; Excludes1 actinomycetoma (B47.1)
Nocardiosis — infection by Nocardia species that can cause actinomycetoma but also causes disseminated pulmonary or CNS infection; coded A43.x; important differential in immunocompromised patients
Osteomyelitis — bone infection that can result from late-stage actinomycetoma spreading from subcutaneous tissue to underlying bone; coded M86.xx with site specificity; must be coded as an additional diagnosis when present
Subcutaneous abscess — a key physical manifestation and hallmark feature of actinomycetoma; forms as the infection progresses through deep dermis and subcutaneous tissue
Granuloma — the histological hallmark of actinomycetoma; granulomatous inflammatory response surrounds the actinomycete grains in the tissue
Actinomyces — the genus of Gram-positive, filamentous bacteria sharing the actino- root; while Actinomyces itself causes actinomycosis (A42.x), related aerobic actinomycetes cause actinomycetoma (B47.1)
Sinuses (draining) — pathological sinus tracts communicating between deep tissue and the skin surface; a defining clinical feature of mycetoma through which granule-containing exudate drains
Tumefaction — firm, diffuse swelling of the affected site; one of the three clinical hallmarks of actinomycetoma alongside nodules/abscesses and draining sinuses
🔧 COMMON CPT CODES (Actinomycetoma-Related Diagnosis & Treatment)
CPT Code
Description
87070
Culture, bacterial; any other source except urine, blood, or stool — used for wound/granule culture to identify causative actinomycete
87186
Susceptibility studies, antimicrobial agent; microdilution or agar dilution (MIC), each multi-antimicrobial per plate — critical for guiding prolonged antibiotic therapy
86602
Antibody; Actinomyces — serologic testing to confirm actinomycete infection
Incision and drainage of abscess; complicated or multiple — for advanced/recurrent abscess drainage
27640
Partial excision (craterization, saucerization, or diaphysectomy) bone; tibia — for osseous involvement requiring bone resection
⚠️ Coding Note:B47.1 has no site-specificity or laterality requirements in ICD-10-CM — it is a single, specific billable code for all anatomic locations of actinomycetoma, so no 7th character extension is needed. When osteomyelitis is documented as a complication (bone involvement in advanced cases), code the osteomyelitis separately with the appropriate M86.xx code with site specificity as an additional diagnosis. A critical undercoding alert: actinomycetoma is frequently under-documented in inpatient settings because it presents looking like a nonspecific soft tissue infection, abscess, or osteomyelitis — if the attending documents “chronic draining wound with granules,” “Madura foot,” “nocardial infection of subcutaneous tissue,” or “actinomycotic lesion,” that is your documentation trigger to query for actinomycetoma (B47.1) rather than defaulting to an abscess or cellulitis code. Be aware that A42.89 (other actinomycosis) specifically Excludes1 actinomycetoma — do not code both; use B47.1 when the subcutaneous/cutaneous form is present. For profee inpatient claims, if the physician manages the infection medically (antibiotics) and a surgical debridement or I&D is performed, both the E/M and the procedure CPT can be reported with a modifier -25 on the E/M if decision for procedure was made same day.
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