Wednesday, August 13, 2025

SPOROTRICHOSIS: CHRONIC FUNGAL INFECTION

Sporotrichosis: The “Rose Gardener’s Disease”

~Introduction

Sporotrichosis is a chronic fungal infection of the skin, subcutaneous tissue, and sometimes deeper structures such as lymphatic vessels, joints, and lungs. It is caused by dimorphic fungi belonging to the Sporothrix schenckii complex. The infection typically occurs when fungal spores enter the body through small skin injuries, often from plant material such as thorns, splinters, or moss.

Due to its frequent association with gardeners, florists, and agricultural workers, sporotrichosis is sometimes called “rose gardener’s disease”. Although cutaneous disease is the most common presentation, sporotrichosis can also appear in pulmonary or disseminated forms, especially in immunocompromised individuals.

~History

First described in 1898 by Benjamin Schenck in Baltimore, USA.
Initially recognized as a rare occupational hazard among gardeners and agricultural workers.
Outbreaks have been reported in various countries, notably a large zoonotic outbreak in Brazil linked to infected cats.

~Epidemiology

Geographic Distribution

Sporotrichosis is found worldwide but is most common in:

Tropical and subtropical climates
South and Central America (especially Brazil, Mexico, Colombia, Peru)
South Africa
Japan
Some parts of Australia and North America

At-Risk Groups

Agricultural workers
Gardeners and florists
Forestry workers
Miners
Veterinarians and cat owners (in regions with zoonotic outbreaks)

~Etiology

The infection is caused by fungi in the Sporothrix schenckii complex, which includes:

Sporothrix schenckii sensu stricto
Sporothrix brasiliensis
Sporothrix globosa
Sporothrix mexicana

These are thermally dimorphic fungi:

At 25°C (environment): grow as mold with slender hyphae and conidia arranged in a "rosette" pattern.
At 37°C (in human tissue): grow as cigar-shaped or oval yeast cells.

~Transmission

Sporotrichosis is acquired through:

Traumatic inoculation – spores enter through cuts, punctures, or scratches.
Zoonotic transmission – scratches or bites from infected animals, especially cats.
Inhalation – rare, leads to pulmonary sporotrichosis.
Nosocomial spread – extremely rare, through contaminated medical materials.

Person-to-person transmission is exceedingly rare, except in the case of cat-to-human infection.

~Pathogenesis

Inoculation – spores from contaminated plant or soil enter the skin.
Local infection – fungus transforms to yeast form at body temperature.
Lymphatic spread – fungi travel along lymphatic vessels, forming nodular lesions.
Granulomatous reaction – immune cells form granulomas around yeast cells.
Chronicity – lesions may persist for months or years without treatment.

~Clinical Forms

Sporotrichosis presents in several forms, depending on the route of infection and host immunity.

1. Cutaneous-Lymphatic Form (most common)

Begins as a painless papule at the site of trauma (usually on hand or forearm).
Lesion ulcerates, forming a painless nodule with a raised edge.
Additional nodules appear along lymphatic channels (lymphocutaneous spread).
May be accompanied by mild lymph node swelling.

2. Fixed Cutaneous Form

Localized skin lesion at the site of inoculation.
No lymphatic spread.
More common in individuals with partial immunity.

3. Disseminated Cutaneous Form

Multiple lesions on various parts of the body.
Usually seen in immunocompromised patients.

4. Pulmonary Sporotrichosis

Caused by inhalation of spores.
Presents with cough, chest pain, fever, weight loss.
Often misdiagnosed as tuberculosis.

5. Extracutaneous/Disseminated Form

Rare, occurs when infection spreads to bones, joints, CNS.
Associated with severe immunosuppression (HIV/AIDS, transplant recipients).

~Symptoms

Painless, slowly enlarging nodules or ulcers.
Lesions may be crusted or have a purulent discharge.
Redness and mild tenderness possible.
In lymphocutaneous form: chain-like distribution of nodules.
In pulmonary form: chronic cough, hemoptysis, respiratory difficulty.
In disseminated form: fever, malaise, organ-specific symptoms.

~Complications

Secondary bacterial infections.
Chronic ulceration and scarring.
Joint destruction (in osteoarticular sporotrichosis).
Meningitis (rare but severe complication in CNS involvement).

~Diagnosis

Diagnosis is based on clinical suspicion and laboratory confirmation.

1. Direct Microscopy

Skin scrapings or pus examined with KOH may rarely show cigar-shaped yeast cells.
Sensitivity is low.

2. Culture

Gold standard for diagnosis.
Specimens cultured on Sabouraud dextrose agar at 25°C and 37°C.
Typical mold growth at 25°C and yeast form at 37°C.

3. Histopathology

Granulomatous inflammation with mixed infiltrate.
PAS and GMS stains reveal yeast cells.
Splendore-Hoeppli phenomenon may be present.

4. Serological Tests

Not widely used for routine diagnosis; more useful in research or severe cases.

5. Molecular Tests

PCR can identify species within the Sporothrix complex.

~Differential Diagnosis

Conditions that can mimic sporotrichosis include:

Cutaneous leishmaniasis
Mycobacterium marinum infection
Nocardiosis
Cutaneous tuberculosis
Actinomycosis
Chromoblastomycosis

~Treatment

Treatment depends on the form of disease and the patient’s immune status.

1. First-Line: Itraconazole

100–200 mg/day orally for 3–6 months for cutaneous disease.
Longer treatment (up to 12 months) for osteoarticular or disseminated forms.

2. Potassium Iodide (KI)

Saturated solution of potassium iodide (SSKI) effective for cutaneous disease.
Used more in resource-limited settings.
Side effects: metallic taste, salivary gland swelling, gastrointestinal upset.

3. Alternative Antifungals

Terbinafine: 250–500 mg/day.
Posaconazole or voriconazole for resistant cases.

4. Amphotericin B

Used for severe disseminated or CNS disease.
Liposomal formulation preferred for reduced toxicity.

5. Supportive Therapy

Wound care and prevention of secondary infection.

~Prognosis

Cutaneous forms: Excellent prognosis with early treatment.
Disseminated forms: Guarded prognosis, especially in immunocompromised patients.
Relapse possible if treatment is incomplete.

~Prevention

Wear gloves, long sleeves, and protective footwear when handling plants, soil, or moss.
Prompt cleaning and disinfection of skin injuries.
Educating at-risk occupational groups.
Control of feline sporotrichosis in endemic areas.

~Public Health Perspective

Neglected Mycosis

Sporotrichosis is underreported in many countries.
Outbreaks in Brazil caused by S. brasiliensis spread from cats to humans have highlighted the zoonotic risk.

Challenges

Delayed diagnosis due to lack of awareness.
Limited availability of antifungal drugs in rural areas.
Veterinary control of infected cats is complex and costly.

~Case Example

A 42-year-old female florist presented with a 3-month history of a painless ulcer on her right hand, with additional nodules along her forearm. She recalled being pricked by a rose thorn prior to onset. Culture from pus grew Sporothrix schenckii. She was treated with itraconazole 200 mg/day for 5 months, leading to complete healing without recurrence.

~Conclusion

Sporotrichosis is a globally distributed, environmentally acquired fungal infection that most often affects the skin and lymphatic system but can also involve deeper structures. While usually curable with antifungal therapy, delayed diagnosis can lead to prolonged illness and complications. Increased awareness among healthcare workers and at-risk populations, along with early treatment, remains the cornerstone of controlling this neglected mycosis.