Question
Sporotrichosis.
Answer
Sporotrichosis: a chronic subcutaneous mycosis caused by the dimorphic fungus Sporothrix schenckii.
Source/risk factor: a saprophyte found in soil, decaying vegetation, and plant material (thorns, moss, hay, rose bushes); classically acquired via traumatic inoculation from thorn pricks/plant material handling — hence its association with gardeners, florists, and farmers (“rose gardener’s disease”).
Clinical presentation: begins as a small nodule at the site of inoculation, which ulcerates; classically shows lymphocutaneous spread — a chain of similar nodules develops proximally along the lymphatic drainage pathway from the primary lesion.
Laboratory diagnosis:
- Direct microscopy of biopsy/exudate — may show characteristic cigar-shaped budding yeast forms, though often sparse, sometimes requiring special stains (PAS, GMS).
- Culture — the definitive test; grown on Sabouraud dextrose agar at 25–30°C, producing a mould form with delicate hyphae bearing conidia in a characteristic “rosette/daisy” arrangement; on subculture at 37°C, converts to the yeast (cigar-shaped) form — demonstrating this temperature-dependent dimorphism confirms diagnosis.
- Histopathology — granulomatous/suppurative inflammation, occasionally with an asteroid body (Splendore-Hoeppli phenomenon) around the yeast cells.
Treatment: Itraconazole is the drug of choice for cutaneous/lymphocutaneous disease; saturated solution of potassium iodide (SSKI) is an older, still occasionally used alternative; Amphotericin B is reserved for severe/disseminated disease.