Sporothrix schenckii
From IDWiki
- Dimorphic fungus that causes rose-handler's disease
Background
Microbiology
- Dimorphic fungus with a hyaline, hyphated mold phase at 25ºC, and a round-to-oval budding yeast phase at body temperature
- Produces melanin, a virulence factor
Epidemiology
- Found in soil, decomposing plant matter, and peat moss worldwide
- Acquired by traumatic implantation or inoculation of a preexisting wound
- Can also be acquired by cat scratches
Clinical Presentation
Lymphocutaneous
- Common cause of nodular lymphangitis
- Incubation period 7 to 30 days
- Nodules can be 2 to 4 cm, and appear along the lymphatics, typically in the arms and legs (and face, in children)
- They become indurated, then ulcerated
- May have regional lymphadenopathy
- Usually mild or no systemic symptoms
Fixed cutaneous
- Only a single lesion, fixed at the point of inoculation
- Lesions may be papular, plaques, nodular, verrucoud, or ulcerated
Disseminated or multifocal
- Only occurs in patients with immunodeficiency, including alcoholism, diabetes, sarcoidosis, tuberculosis, transplantation, malignancy, immunosuppressive medication, or advanced HIV
- Lesions can include ulcerations, aceniform, plaques, or crusts
- Worst prognosis is with dissemination to lungs or meninges
Extracutaneous
- Rare presentation without skin lesions, caused either by inhalation or deep inoculation
- Musculoskeletal infections are the most common, with septic arthritis followed by osteomyelitis or tenosynovitis
- Pulmonary sporotrichosis is more common in men aged 30 to 60 years, and presents similarly to pulmonary tuberculosis
- Sporotrichotic meningitis is rare and occurs in immunocompromised patients
- Can also affect eyes, genitals, or oropharyngeal mucosa
Diagnosis
- Sample collection
- Deep swab or aspirate, if possible
- Punch biopsy, can be with sterile saline if needed (not in formalin)
- Direct microscopy
- May see yeast forms or characteristic asteroid bodies (especially from deep swabs)
- Culture
- Sab + chloramphenicol at 25ºC for 5 to 7 days for mold form followed by BHI at 35-37ºC for 5 to 7 days for yeast form
- Colony appearance is a white mold that becomes dark
- Molecular tests
- Some labs have developed PCR diagnostics
- Serology
- Tube or latex agglutination have specificity (95%) and sensitivity (98-100%)
- Immunoassays also exist
- Sporotrichin skin test
- Essentially like a TB skin test but for sporotrichosis
- Only useful for epidemiologic surveys
Management
- First-line: Itraconazole 100 to 200 mg po daily until 2 to 4 weeks after the lesions resolve (around 3 to 6 months)
- Dose may be increased to 400 mg if there's a poor response, there are extracutaneous infections including osteoarticular or pulmonary disease, or the host is immunocompromised
- Alternatives include amphotericin B, fluconazole, and maybe terbinafine
- For pregnant women, use amphotericin B
- For osteoarticular infection, use itraconazole 200 mg po bid
- Can use amphotericin B as induction
- Duration is at least 12 months
- For severe pulmonary infection, use amphotericin B 3 to 5 mg/kg daily (liposomal), stepped down to itraconazole 200 mg po bid when better, to complete at least 12 months total
- Same treatment for disseminated disease
- For meningeal infection, use amphotericin B 5 mg/kg daily for 4 to 6 weeks, followed by itraconazole 200 mg po bid until at least 12 months
- For children, use itraconazole 6 to 10 mg/kg (max 400 mg) daily
- For severe disease in children, use amphotericin B 0.7 mg/kg daily induction then itraconazole 6 to 10 mg/kg (max 400 mg) daily
- Can also do local hyperthermia, especially for patients who are unable to take the above medications
