Risk Factors for Developing Mycosis
- Antibiotic therapy
- Steroids or chemotherapy
- Immunocompromised state as in HIV
- Extreme age groups i.e., very young or very old
Classification of Mycosis
Based upon the level of tissue invasion, mycoses may be divided into the following types:
This infection is limited to the superficial layer of the skin and hair, e. g. Tinea versicolor.
Cutaneous mycosis not only invades deeper into epidermis of the skin but also involves hair and nails of the body. The organisms causing such infection are called dermatophytes, often limited to the keratinized layer of skin, hair and nails. The host immune system may be activated causing local inflammatory changes. Examples include ringworm infection.
Subcutaneous mycosis occurs as a result of piercing trauma to the skin causing the organism to invade the skin, subcutaneous fats, fascia and muscles. Such infections require debridement and treatment with antifungal drugs.
Systemic mycosis can be either due to primary pathogens or opportunistic organisms which are already residing inside the body. In the former case, they are usually inhaled and spread to the local tissues and lymphatic stream causing systemic infection. Opportunistic infections mostly occur in immunocompromised individuals. Examples of the latter include candidiasis, aspergillosis and cryptococcosis.
Sporotrichosis, also known as Rose Gardener’s disease, is a fungal infection caused by the species Sporothrix schenckii shown in the figure. The most common form of sporotrichosis is the cutaneous infection. Pulmonary and disseminated infections, although rare, have also been reported.
Sporotrichosis occurs worldwide. It is endemic in China. Epidemics have been reported in South Africa, Australia and Brazil. The prognosis of the disease is very good.
Morbidity is associated with pulmonary sporotrichosis specifically in patients with chronic obstructive pulmonary disease (COPD) or osteomyelitis developed as a result of dissemination. The mortality rate is significant in immunocompromised patients.
The common mode of transmission of sporotrichosis is through skin inoculation. The dimorphic organism is found in the soil and enters the skin via cuts, wounds, animal bites or scratches.
The initial reddish, necrotic papule of cutaneous sporotrichosis appears after 1-10 weeks of skin injury. A granuloma is formed by the neutrophils, histiocytes and giant cells along with local necrotic tissue. This suppurative area is then surrounded by the lymphocytes and the plasma cells.
The fungal infection spreads via lymphatic stream, direct invasion of local tissues and rarely through blood stream. Haematogenous dissemination, if occurs, causes severe visceral infections including meningitis. The common extracutaneous sites of infection are bones, joints, tendons and bursae.
A rare form of sporotrichosis occurs after inhalation of the organism which causes pneumonia specifically in patients with COPD or alcoholism. Such infections are clinically and radiographically indistinguishable from tuberculosis or histoplasmosis.
The clinical presentation depends upon the immune status of the host. Patients usually present with a primary lesion in the distal extremities. Initially, it is a small nodule which enlarges and becomes pustular and later ulcerates. The lesion is mildly painful with no signs of systemic illness such as fever.
Later on, new lesions begin to appear along the line of lymphatic tracts of the body. The fixed cutaneous lesions of sporotrichosis should be considered if they fail to heal spontaneously or with antibiotics. The hypersensitivity reactions such as erythema nodosum or erythema multiforme are also associated with the disease.
The clinical features of pulmonary sporotrichosis are usually nonspecific and only give clue towards underlying respiratory pathology. The disseminated infection is common in immunocompromised individuals. In such cases, the signs and symptoms depend upon the organ involved.
Sporotrichosis needs to be differentiated from other bacterial and fungal infections of the lungs and joints. The differential diagnosis includes:
- Bacterial pneumonia
The diagnosis of the sporotrichosis can be done by culturing the organisms from specimen such as pus, skin biopsy, CSF and synovial fluid. Periodic acid-Schiff, Gomori methenamine-silver or immunohistochemical staining methods are often used to visualize the organism.
The ratio of CSF to serum antibody against sporotrichosis suggests of meningeal involvement. Similarly, X-ray and CT scan chest point towards respiratory pathology, however, do not give a definitive diagnosis.
Medical approach includes antifungal treatment for all forms of sporotrichosis. Itraconazole per oral is most commonly used for 3-6 months. Supersaturated potassium iodide (SSKI) is also effective against cutaneous sporotrichosis, however, should be avoided in pregnant females.
Topical heat application may also be beneficial as the organism grows better at 35 °C. Patients can perform their routine activity as feasible. In severe cases, intravenous amphotericin B is given followed by itraconazole therapy for 1 year.
Surgical care involves appropriate drainage of affected joints in case of osteoarticular sporotrichosis. Debridement may be done if required. In case of pulmonary sporotrichosis, surgical removal of the affected lung or specific part may be done.
Prevention and follow-up
Sporotrichosis can be prevented with the use of gloves while doing outdoor activities such as gardening. Ideally, animals should also be handled with wearing gloves, to avoid zoonotic transmission. Animals that have skin lesions can easily transmit the disease to humans. Last but not the least, patient education is required regarding the mode of transmission and the adverse effects of antifungal therapy.