Infectious Disease and Microbiology – Curvularia Species

Overview

Curvularia species are dematiaceous (darkly pigmented), filamentous fungi that are uncommon causes of human infection. They most often produce keratitis or cutaneous and subcutaneous infections, although invasive disease involving the lungs, heart, bone, or other deep tissues can rarely occur.

Important species include C. boedijn, C. geniculata, C. lunata, C. pallescens, and C. senegalensis.

Microbiologic Characteristics

Curvularia species are dematiaceous filamentous fungi (molds).

In infected tissues, fungal elements may appear as:

• Yeast-like forms

• Pseudohyphae

• Septate, pigmented hyphae

The presence of melanin within the fungal cell wall produces the characteristic dark pigmentation associated with dematiaceous fungi.

Epidemiology

Human infection with Curvularia is rare.

These organisms are environmental molds, and human disease generally follows exposure or traumatic introduction of fungal material into tissues.

Keratitis

Fungal keratitis is an important manifestation of Curvularia infection.

Infection may follow corneal trauma, particularly when the eye has been exposed to environmental or plant material.

Clinical manifestations may include:

• Eye pain

• Redness

• Photophobia

• Excessive tearing

• Corneal ulceration

• Reduced visual acuity

Severe infection can threaten vision if not recognized and treated promptly.

Skin and Subcutaneous Tissue Infection

Curvularia may cause localized cutaneous or subcutaneous fungal infection, often following traumatic inoculation.

Patients may develop:

• Nodules

• Plaques

• Ulcerative lesions

• Cysts or abscess-like lesions

• Chronic localized inflammation

These infections fall within the broader spectrum of disease caused by dematiaceous fungi.

Deep-Tissue Infection

Deep invasive disease is uncommon but may occur, particularly in patients with impaired host defenses.

Reported manifestations include:

• Pneumonia

• Endocarditis

• Osteomyelitis

Other organs may occasionally become involved in disseminated disease.

Phaeohyphomycosis

Infections caused by dematiaceous fungi in which pigmented septate hyphae or yeast-like fungal elements are demonstrated in tissue are generally classified within the spectrum of phaeohyphomycosis.

Thus, Curvularia species are important potential causes of phaeohyphomycotic infection.

Diagnosis

Diagnosis is primarily established through:

• Tissue biopsy

• Fungal culture

Both methods are useful because histopathology demonstrates tissue invasion while culture helps identify the specific fungal organism.

Tissue Biopsy

Histopathologic examination may demonstrate pigmented, septate fungal hyphae, pseudohyphae, or yeast-like elements within infected tissue.

The pigmentation provides an important clue that the infection is caused by a dematiaceous fungus.

Culture

Fungal culture allows identification of Curvularia species and helps distinguish the organism from other pigmented molds.

Clinical specimens should be obtained directly from the involved tissue whenever possible.

Treatment

Historically, amphotericin B has been used for serious Curvularia infections.

Treatment depends on:

• Site of infection

• Severity

• Degree of tissue invasion

• Immune status

• Antifungal susceptibility

Additional Treatment

Azole antifungal agents have also been used for infections caused by dematiaceous fungi.

However, the source notes that clinical data regarding their effectiveness against Curvularia are limited.

Whenever possible, treatment of serious disease should be guided by fungal identification and antifungal susceptibility information.

Surgical Management

Localized infections may also benefit from surgical excision or debridement, particularly when there is extensive infected or necrotic tissue.

Keratitis requires prompt ophthalmologic management because progressive corneal disease can result in permanent visual impairment.

High-Yield Clinical Pattern

Environmental or plant-related trauma

• ●

Keratitis or chronic subcutaneous lesion

• ●

Pigmented, septate fungal hyphae in tissue

→ Think dematiaceous fungal infection such as Curvularia

Exam Essentials

Genus: Curvularia

Type: Dematiaceous filamentous fungus

Pigmentation: Darkly pigmented fungal elements

Tissue morphology: Yeasts, pseudohyphae, or septate pigmented hyphae

Frequency: Rare human pathogen

Common manifestations: Keratitis and skin/subcutaneous infection

Rare invasive infections: Pneumonia, endocarditis, osteomyelitis

Disease category: Phaeohyphomycosis

Diagnosis: Tissue biopsy + fungal culture

Traditional treatment: Amphotericin B

Other therapy: Azoles have been used, but supporting data are limited

Key clinical pearl: Curvularia is a dematiaceous mold that should be considered when pigmented septate hyphae are found in a patient with fungal keratitis or a chronic cutaneous/subcutaneous infection.