Pulmonary Scedosporium and Lomentospora infections

Pulmonary Scedosporium and Lomentospora infections ¹¹ are opportunist pulmonary fungal infections which can present as local or disseminated disease.

Epidemiology

These fungi are found in areas of high human impact, living in soil and polluted water. Organisms can be introduced by penetrating trauma, near-drowning or inhalation. 

Immunocompromised patients are susceptible to invasive disease and disseminated infection which can progress rapidly and is usually fatal. Those most at risk include:

• neutropaenic patients during pre-engraftment phase of hematologic stem cell transplant (HSCT)

• lung and other solid organ transplant recipients, especially if immunosuppressed for graft-versus-host disease (GVHD)

• acute leukemia

• advanced HIV

• cancer patients on immunosupression

• primary immunodeficiencies ¹³

These organisms may account for 25% of non-Aspergillus mold infections in transplant patients. 

Some species cause chronic inflammation in cystic fibrosis/bronchiectasis, allergic bronchopulmonary mycosis (ABPM) or mycetoma. 

Lomentospora prolificans (previously known as Scedosporium prolificans) causes disease in Spain and Australia. The ability to conidiate in host tissue leads to rapid progression and dissemination.

Pathology

There are several pathological species, more commonly:

• Lomentospora prolificans

• Scedosporium apiospermum

• Scedosporium boydii

• Scedosporium aurantiacum

Stem cell transplant patients are particularly at risk. In healthy people, inhaled fungal conidia are removed by the muco-ciliary escalator and macrophages. Remaining conidia germinate into hyphal forms which are normally eliminated by neutrophils through the release of reactive oxygen species and extracellular traps. In neutropaenic patients hyphae invade tissues and infiltrate vasculature, leading to extensive tissue infarction and fungal dissemination. These organisms are resistant to commonly used antifungal drugs ¹².

Clinical presentation

Infection may present with fever, dyspnea or extra-pulmonary disease such as endocarditis, sinus disease, brain abscess, meningitis or ventriculitis.

Radiographic features

These vary according to the immune status of the individual and include manifestations of:

• ABPM

• cavitating lung lesions containing mycetomas ⁸

• rapidly invasive necrotizing infections which demonstrate a 'bird's nest’ appearance on CT, i.e. a progressively expanding ill-defined rounded opacity with relative central radiolucency and non-enhancing vessels and parenchyma

Treatment and prognosis

Scedosporium/Lomentospora infections in transplant recipients have high rates of dissemination and a poor overall outcome.  These molds are resistant to traditional antifungal agents but may respond to voriconazole or combination therapy. Rapidly invasive fungal infections may require thorough surgical debridement.