Infectiology & Dermatology & Family Medicine
Sporotrichosis
Sporotrichosis is a subcutaneous mycosis—a deep fungal infection of the skin and subcutaneous tissues—caused by the complex Sporothrix schenckii (Dimorphic fungus: filamentous in the environment + yeast-like at 37°C in human tissues), present in soil + decaying vegetation + peat moss + rotten wood + rose thorns + straw + and ornamental plants. Contamination most often occurs by transcutaneous traumatic inoculation during a wound from a thorn + splinter + animal bite + or contact with contaminated soil — without the patient always remembering it clearly (the initial wound may be minimal). Sporotrichosis is nicknamed «rose gardener's disease» or «rose-thorn disease» in English, although it can affect farmers + horticulturists + miners + foresters + florists + and anyone working with plants or soil. The most common clinical form is cutaneous-lymphatic sporotrichosis — characterized by the appearance of a painless or slightly painful nodule at the inoculation site that progressively evolves into ulceration + followed by the emergence of secondary nodules in a chain along the ascending lymphatic pathway (lymphangitic sporotrichosis — quasi-pathognomonic) — the progression of which can be extremely slow (weeks to months) and the diagnosis of which is often delayed because it is confused with bacterial skin infections + cutaneous leishmaniasis + or mycobacteriosis. Disseminated sporotrichosis (bones + joints + lungs + meninges) is rare and occurs almost exclusively in severely immunocompromised individuals (HIV/AIDS with very low CD4 counts + prolonged corticosteroid therapy + alcoholism + severe diabetes). Oral itraconazole is the reference treatment for cutaneous forms with excellent results.
Clinical forms
| Shape | Frequency | Clinical presentation | Treatment |
|---|---|---|---|
| Cutaneous-lymphatic (lymphangitic) | 70–75% of cases + most common form | Painless primary nodule at the inoculation site (hand + forearm ++ + finger) → central ulceration + crust + then multiple secondary nodules in a chain, ascending along the lymphatic pathway (rosary-like lymphangitis) → each nodule may ulcerate + fistulize + exude | Itraconazole 200 mg/day x 3-6 months |
| Fixed cutaneous (localized) | 20–25 % cases | Single ulcerated or verrucous lesion at the inoculation site + WITHOUT lymphatic spread + frequent in endemic areas where immunity is acquired + may resemble squamous cell carcinoma + or cutaneous leishmaniasis | Itraconazole 200 mg/day × 3–6 months + or local thermotherapy (40–42 °C heat) if itraconazole is contraindicated |
| Pulmonary | < 5 % — inhalation of conidia | Cough + hemoptysis + pulmonary cavitation (resembles tuberculosis) + apical excavatum + immunocompromised + alcoholic + coal miner ++ → risk of confusion with tuberculosis or histoplasmosis | Itraconazole 200 mg twice daily for 12 months or liposomal amphotericin B (severe forms) |
| Osteoarticular | < 5 % — hematogenous spread | Chronic septic arthritis (knee + wrist + ankle) + osteomyelitis + immunocompromised + often confused with rheumatoid arthritis or bacterial septic arthritis | Itraconazole 200 mg twice daily for a minimum of 12 months + surgical drainage if necessary |
| Disseminated (CNS + multi-organ) | Very rare — AIDS-stage HIV + very low CD4 | Fungal meningitis + disseminated skin lesions + liver involvement + spleen involvement + poor prognosis without rapid treatment | Lipid Amphotericin B (AmBisome®) 3–5 mg/kg/day IV → induction + switch to itraconazole after stabilization + extended duration |
Diagnosis
- Mycological culture (gold standard): Pus or material collection from the ulcerated lesion + skin biopsy → Sabouraud medium culture at 25–28 °C → white to cream filamentous colony → then culture at 37 °C → yeast-like conversion (dimorphism confirms the genus Sporothrix) → identification by MALDI-TOF or ITS sequencing + incubation time: 7 to 14 days → no growth on standard temperature media.< 25°C (essentially)
- Histopathology (skin biopsy): suppurative granuloma + giant cells + asteroid bodies (Splendore-Hoeppli phenomenon — hypersensitivity reaction around the fungus) + budding yeasts Sporothrix (few → NOT + Grocott-Gomori + Mayer-Mucicarmine) → direct yeast search is often negative (low fungal burden) → culture remains essential
- Serology: tests ELISA (IgG + IgM anti-Sporothrix) → useful for diagnosing disseminated or extradermal forms + sensitivity of 80–90% in disseminated forms + less useful in localized cutaneous forms
- PCR : available in certain reference laboratories + rapid identification of the complex Sporothrix schenckii + useful if culture is negative or results are ambiguous
Differential diagnosis — sporotrichoid syndrome
- Sporotrichoid pattern: Several infectious agents can mimic lymphocutaneous sporotrichosis with ascending nodular lesions, and the presentation is so characteristic that it deserves its own name (sporotrichoid syndrome or nodular lymphangitis syndrome).
- Mycobacterium marinum contact with water + aquariums + fish + lesions very similar to sporotrichosis → mycobacterial culture + PCR + no response to itraconazole → clarithromycin + ethambutol
- Cutaneous leishmaniasis Travel to an endemic area + vector (sandfly) + smear + Leishmania culture + PCR
- Cutaneous nocardiosis Nocardia brasiliensis Immunocompromised + Latin America + multiple fistulas + sulfur granules + bacteriological culture (slow-growing aerobic Nocardia)
- Cutaneous tularemia: Contact with hare, rabbit, rodent, hunting, inoculation ulcer, regional adenopathy, Francisella tularensis serology
ℙ️
Sporotrichosis is the main cause of a skin lesion with ascending rosary-like nodules along a lymphatic pathway (sporotrichoid syndrome), but several other agents can mimic it— Mycobacterium marinum (aquariums + fish) is the most frequent differential diagnosis in Canada. Always ask the patient about recent exposures: gardening + roses + thorns + aquariums + contact with animals + travel to tropical areas. Mycological culture on a specialized medium at two temperatures is essential to confirm the diagnosis.
Treatment
- Itraconazole (standard treatment - cutaneous forms): 200 mg/day orally × 3–6 months (cutaneous-lymphatic forms) + take with meals or an acidic beverage (absorption is improved in an acidic environment) + monitor for drug interactions (numerous interactions via CYP3A4 — statins + oral anticoagulants + antiarrhythmics) + efficacy: cure in 90–95% of cutaneous forms + monitoring of liver transaminases (rare hepatotoxicity)
- Terbinafine 500 mg/day: alternative to itraconazole + comparable efficacy in cutaneous-lymphatic forms (recent meta-analyses) + few drug interactions + good tolerability
- Saturated solution of potassium iodide (SSKI) Historical treatment still used in low-resource countries + exact mechanism not well understood + effective but significant adverse effects (metallic taste + nausea + iododerma + hypothyroidism) + declining use in developed countries
- Local thermotherapy: local heat application (104–107.6 °F × 30 min × 2/day) → Sporothrix is thermosensitive → option in local forms if itraconazole is contraindicated (pregnancy + interactions) + or as a supplement to antifungal treatment
- Severe disseminated forms: Liposomal amphotericin B (Ambisome®) 3–5 mg/kg/day IV until clinical stabilization + then switch to itraconazole 200 mg BID × 12 months minimum
- Pregnancy: Itraconazole contraindicated (teratogenic) → local thermotherapy for localized cutaneous forms + liposomal amphotericin B for severe forms + after childbirth → itraconazole
Medical consultation recommended
Consult a doctor if a painless skin nodule appears after an injury from a thorn, splinter, or contact with soil or plants, especially if it ulcerates and new nodules appear along the arm or leg, spreading upwards. This presentation suggests sporotrichosis, requiring a skin biopsy, fungal culture, and antifungal treatment. For the evaluation of a chronic post-traumatic skin lesion and itraconazole prescription, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's nurse practitioners (NPs) recognize the clinical presentation of sporotrichosis (nodular lesion + chain of ascending lymphatic nodules + gardening or vegetation contact history), prescribe a skin biopsy + fungal culture at two temperatures, initiate treatment with itraconazole 200 mg/day for cutaneous forms, refer to infectious diseases or dermatology for atypical or refractory forms, and manage itraconazole drug interactions. Consultations are available at several service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is for informational purposes only and does not replace the advice of a doctor or an infectious disease specialist. Sporotrichosis requires diagnostic confirmation by mycological culture before initiating antifungal treatment. Itraconazole is contraindicated during pregnancy. The duration of treatment should not be shortened even if the lesions appear healed – the risk of relapse is high if treatment is stopped prematurely.
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