Sporotrichosis

A 45-year-old farmer presented with multiple nodules over the right forearm. The lesion began as a single painless, erythematous papule 6 months ago. The papule progressed to form a nodule, and was followed by the appearance of additional papules and nodules extending proximally towards the right elbow in a linear fashion (Figure). He had tetanus vaccination in the right arm 2 years ago. He did not recall a history of trauma to the right forearm. He was otherwise healthy. 

Physical examination revealed multiple discrete, nontender, erythematous nodules of varying size over the right forearm, along the course of lymphatic drainage extending proximally towards the right elbow. Lymph nodes in the right epitrochlear and axillary areas were enlarged. The rest of the examination was unremarkable. 

Introduction. Sporotrichosis, commonly known as rose gardener’s disease, is a cutaneous, subcutaneous, or systemic mycosis caused by the dimorphic fungus Sporothrix schenckii.¹ The condition was first described in 1898 by Benjamin Schenck who described a man with multiple ascending nodules on the forearm proximal to a lesion in the right index finger that appeared after a puncture wound.² He cultured the causative organism and, with the aid of Erwin Smith, identified and classified it as sporotrichia. In 1900, Hektoen and Perkins described the morphology of the organism and named it S schenckii.³

The Organism. S schenckii is a dimorphic fungus that exists in a yeast form at 37°C and in a hyphal form at room temperature. The organism grows in the filamentous phase on Sabouraud dextrose agar at 25°C to 28°C, producing cream-colored colonies in 5 to 8 days. A few days later, the colonies become dark brown. 

Dimorphic fungi exist in the mold form in the environment and are typically infectious. Once the conidia are introduced into the body by traumatic injury or inhalation, the organisms convert to the yeast phase.⁴

Epidemiology. S schenckii is found throughout the world in soil and decaying vegetation. Sporotrichosis is more frequent in temperate areas (25°C-28°C) with high humidity (80%-95%).⁵ The disease can affect persons of all ages but is more frequent in young adults.⁵

The classical transmission is via traumatic inoculation of the fungus into the skin through contact with contaminated material.¹ Gardeners, florists, farmers, and miners are at risk of getting the disease.¹ Predisposing factors include alcoholism, diabetes mellitus, and immunosuppression.⁶ Other forms of transmissions include inhalation of the fungus and zoonotic spread from scratches and bites from infected animals, notably cats.^1,4 

Histopathology. Histologically, there is granulomatous inflammation associated with epithelial hyperplasia and a histiocytic plasma cell infiltrate.⁷ Characteristic features, such as cigar-shaped yeasts and asteroid bodies (round or budding yeast surrounded by eosinophilic spicules), are not always present.⁸

Clinical manifestations. The incubation period is variable, ranging from 7 to 30 days, with most cases manifesting within the first 3 weeks of exposure.^4,6 Clinically, sporotrichosis can be classified into 4 categories: lymphocutaneous, fixed cutaneous, multifocal or disseminated cutaneous, and extracutaneous.⁸ 

The lymphocutaneous form accounts for approximately 75% of all cases of sporotrichosis, followed by the fixed cutaneous form.⁵ The multifocal or disseminated cutaneous and extracutaneous forms are very rare and occur mainly in immunocompromised individuals, especially HIV+ ones.⁹

Typically, the lymphocutaneous form presents with a papule at the site of inoculation, most commonly on the limbs, and, in children, the face. Progressive induration leads to nodule formation with or without ulceration.⁷ With time, additional lesions develop more proximally along the path of lymphatic drainage, as is illustrated in the present case.¹⁰ Systemic symptoms, if present, are usually mild. Regional lymphadenopathy may occur.

Fixed cutaneous sporotrichosis presents as an asymptomatic nodule or plaque, localized to the site of injury. The lesion often has a granulomatous, verrucous, or ulcerated appearance.¹⁰ This form most commonly occur on the face, neck, or legs.¹⁰ Fixed cutaneous sporotrichosis probably reflects the high degree of immunity of the affected individual.

The multifocal or disseminated cutaneous form presents with numerous scattered lesions such as nodules, cysts, and ulcerations.⁸ It results from the hematogenic dissemination of the pathogen from the site of inoculation to the skin without systemic spread and lymphatic involvement.⁶

The extracutaneous form is caused by inhalation of spores or hematogenous dissemination from a deep inoculation site.^7,8 It can present as pulmonary sporotrichosis, osteoarticular infection, monoarthritis, tenosynovitis, meningitis, and ocular sporotrichosis.⁸ 

Diagnosis. The gold standard for diagnosis is the isolation of the fungus in Sabouraud agar. Material from the cutaneous lesion may be aspirated or scraped or biopsied and sent for such purpose. Demonstration of the mold form at 25°C and the yeast form at 37°C is necessary for definite diagnosis.⁴ 

Differential diagnosis. The differential diagnosis of cutaneous sporotrichosis include pyoderma, catscratch disease, folliculitis, mycobacterial diseases, leishmaniasis, tularemia, nocardiosis, mycetoma, chromoblastomycosis, and syphilis.

Management. For lymphocutaneous and fixed cutaneous sporotrichosis, oral itraconazole 200 mg daily is the drug of choice.^1,9 Alternative antifungal agents—such as terbinafine, a longer course of itraconazole, or saturated solution of potassium iodide initiated at a dosage of 5 drops 3 times a day and increasing to 40 to 50 drops 3 times daily as tolerated—can be used if treatment is unsuccessful.^9,10 

Disseminated and extracutaneous sporotrichosis are treated with amphotericin B as a first-line agent, followed by oral itraconazole for maintenance therapy.⁷ In instances in which systemic agents cannot be given such as pregnancy, heat therapy may be considered. Heat therapy typically takes the form of hot baths (temperature of 45°C) 3 times a day.⁵

References: 

1.Cordeiro FN, Bruno CB, Paula CD, et al. Familial occurrence of zoonotic sporotrichosis. An Bras Dermatol. 2011;86(4 Suppl 1):S121-S124.

2.Schenck BR. On refractory subcutaneous abscesses caused by a fungus possibly related to the sporotrichia. Johns Hopkin Hosp Bull. 1898;9:286-290.

3.Hektoen L, Perkins CF. Refractory subcutaneous abscesses caused by Sporothrix schenckii: a new pathogenic fungus. J Exp Med. 1900;5:77-89. 

4.Rees RK, Swartzberg JE. Feline-transmitted sporotrichosis: a case study from California. Dermatol Online J. 2011;17(6):2.

5.Bonifaz A, Saul A, Paredes-Solis V, et al. Sporotrichosis in childhood: clinical and therapeutic experience in 25 patients. Pediatr Dermatol. 2007;
24(4):369-372

6.Vasquez-del-Mercado E, Arenas R, Padilla-Desgarenes C. Sporotrichosis. Clin Dermatol. 2012;
30(4):437-443.

7.Ramos-e-Silva M, Vasconcelos C, Carneiro S, et al. Sporotrichosis. Clin Dermatol. 2007;
25(2):181-187.

8.Zhang YQ, Xu XG, Zhang M, et al. Sporotrichosis: clinical and histopathological manifestations. Am J Dermatopathol. 2011;33(3):296-302.

9.Kauffman CA, Bustamante B, Chapman SW, et al. Clinical practice guidelines for the management of sporotrichosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007;45(10):1255-1265.

10.Mahlberg MJ, Patel R, Rosenman K, et al. Fixed cutaneous sporotrichosis. Dermatol Online J. 2009;15(8):5.