Conditions · Infectious and tropical diseases
Sporotrichosis and other subcutaneous mycoses !
Sporotrichosis is a fungal skin infection that enters through a thorn prick or cat scratch and spreads as nodules along the arm's lymph vessels.
Updated 2026-11-01
Structures involved
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Microorganisms that cause it
Why it happens
- Granulomatous inflammation: caseating vs non-caseating, the causes to know
- How the lymphatic system works
- Lymphatic vessels
What it is
Subcutaneous mycoses are fungal infections implanted into the skin and subcutaneous tissue by minor trauma. Sporotrichosis, the most common, causes a nodule at the inoculation site and a chain of nodules along the lymphatics of the limb. Chromoblastomycosis (slow verrucous plaques) is included here; mycetoma has its own page.
Who gets it
Sporotrichosis is the most frequent subcutaneous mycosis in Latin America. In Colombia it is classically acquired from plants, soil and wood in rural workers and gardeners, especially in Andean areas. In Brazil a cat-transmitted epidemic by Sporothrix brasiliensis has spread to neighbouring countries. Chromoblastomycosis affects rural workers in humid tropical areas.
Causes
- Sporothrix schenckii complex, a dimorphic fungus in soil, plants, moss and wood
- Sporothrix brasiliensis transmitted by scratches and bites from infected cats
- Chromoblastomycosis: pigmented fungi such as Fonsecaea and Cladophialophora
- Inoculation through thorn pricks, splinters or scratches
Risk factors
- Gardening, farming, forestry, handling rose bushes, hay or moss
- Contact with sick cats (veterinarians, cat owners)
- Walking barefoot or working without gloves in rural areas
- Diabetes, alcohol use disorder, COPD or HIV for severe or disseminated forms
Pathophysiology
The fungus enters through a break in the skin and converts at body temperature to a yeast form. It causes a mixed suppurative and granulomatous reaction at the site and then travels along lymphatic vessels, producing new nodules toward the regional nodes. In chromoblastomycosis the fungus forms thick-walled pigmented sclerotic (muriform) bodies that cause chronic verrucous hyperplasia and fibrosis.
Classification
- Lymphocutaneous sporotrichosis (most common)
- Fixed cutaneous sporotrichosis (single plaque, more common in previously exposed people)
- Extracutaneous or disseminated sporotrichosis: eye, lung, bone, joints, meninges
- Chromoblastomycosis: nodular, verrucous, plaque or cicatricial lesions
Symptoms and signs
- Painless papule or nodule at the site of a thorn prick or scratch, 1 to 12 weeks later
- The nodule ulcerates and drains a little fluid
- New nodules appear in a line along the forearm and arm toward the armpit
- Little fever or systemic illness
- Conjunctivitis after cat-related exposure in the eye
- Chromoblastomycosis: slowly growing warty, cauliflower-like plaques on the foot or leg
Diagnosis
- Clinical
- Suspected with nodules ascending along the lymphatics of a limb after plant or cat exposure (sporotrichoid pattern).
- Tests
- Culture of pus or biopsy is the reference test; PCR identifies the species. Biopsy may show yeasts, cigar-shaped forms or asteroid bodies, though organisms are scarce. In chromoblastomycosis, potassium hydroxide preparation shows the characteristic copper-coloured sclerotic bodies. HIV test in severe forms.
- Imaging
- Not needed for skin disease; chest imaging and bone or joint imaging when extracutaneous disease is suspected.
Differential diagnosis
- Cutaneous leishmaniasis (also gives a sporotrichoid pattern in Colombia)
- Atypical mycobacterial skin infection (Mycobacterium marinum)
- Nocardiosis
- Bacterial skin abscess or cellulitis
- Mycetoma and cutaneous tuberculosis
- Squamous cell carcinoma for chronic verrucous plaques
Goal of treatment
Cure the skin and lymphatic infection with prolonged antifungal treatment, recognise and treat disseminated disease, and limit transmission from infected animals.
Treatment
- Medical
- Oral itraconazole is first line for cutaneous and lymphocutaneous sporotrichosis, continued for weeks after lesions heal, usually 3 to 6 months or more; terbinafine or saturated potassium iodide are alternatives.
- Medical
- Amphotericin B for severe, disseminated or meningeal disease and in some pregnancies, followed by itraconazole; longer treatment in pulmonary and disseminated forms.
- Procedure
- Local heat or cryotherapy for some lesions and in pregnancy; cryotherapy or excision combined with antifungals for chromoblastomycosis.
- Follow-up
- Follow-up until clinical cure, glove use during wound care, and referral of infected cats for veterinary treatment.
Drugs for this condition
Complications
- Secondary bacterial infection of ulcers
- Scarring and chronic lymphoedema
- Osteoarticular and pulmonary sporotrichosis
- Disseminated disease and meningitis in immunosuppressed people
- Squamous cell carcinoma in long-standing chromoblastomycosis
Prognosis
Cutaneous and lymphocutaneous sporotrichosis is usually cured with treatment, although it takes months. Disseminated and meningeal forms in HIV have high mortality. Chromoblastomycosis is chronic and difficult to eradicate, with frequent relapses.
Prevention
- Gloves, long sleeves and closed shoes when handling plants, soil or wood
- Avoiding contact with cats that have skin lesions; gloves for handling them
- Prompt treatment of infected animals
Test yourself
Think of the answer, then tap the question to see it.
What is the typical presentation of sporotrichosis?
A nodule at the inoculation site followed by a chain of nodules along the lymphatics of the limb.
Which exposure is classically linked to sporotrichosis, and which newer source is spreading in South America?
A rose thorn or plant injury; in South America, scratches from infected cats (Sporothrix brasiliensis).
What is the first-line treatment for lymphocutaneous sporotrichosis?
Oral itraconazole for several months.
What microscopic finding defines chromoblastomycosis?
Copper-coloured, thick-walled sclerotic (muriform) bodies.
Which parasitic disease common in Colombia can also cause a sporotrichoid pattern?
Cutaneous leishmaniasis.
Related conditions
- Leishmaniasis
- Mycetoma (actinomycetoma and eumycetoma)
- Cellulitis of the leg
- Abscess, furuncle and carbuncle
- Paracoccidioidomycosis
- Endemic mycoses: blastomycosis and coccidioidomycosis
- Bartonella infections (cat-scratch disease, Carrion disease)
- HIV infection and AIDS
- Dermatophytosis (tinea) and onychomycosis
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Sporotrichosis Basics | Sporotrichosis | CDC (Centers for Disease Control and Prevention, 2024); Clinical Overview of Sporotrichosis | Sporotrichosis | CDC (Centers for Disease Control and Prevention, 2024).
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