Case 1 introduction

[43.1] Pneumocystis carinii is now considered a fungus. Which of the following statements accurately describes this organism?

[43.2] Which of the following statements best describes the laboratory diagnosis of Pneumocystis carinii?

[43.3] Pneumocystis carinii produces disease under what conditions listed below?

[43.1] E. Pneumocystis carinii is often reported as the organism responsible for the described case. Evidence points to P. carinii being primarily found in rats, whereas P. jirovecii is the human species. These species are not grown in the laboratory and do not respond to traditional antifungal chemotherapy. Being found primarily in the lungs, respiratory infections occur in immunocompromised individuals, and dissemination is rare. Specimens of bronchoalveolar lavage, lung biopsy, or induced sputum are stained (Giemsa or methenamine silver, e.g.) and examined for cysts or trophozoites.

[43.2] D. Because Pneumocystis species are not able to be grown in the laboratory, staining procedures constitute the primary diagnostics techniques used. See the answer to Question 43.1 for further discussion.

[43.3] B. Pneumocystis carinii and P. jirovecii are present in the lungs of many animals, including humans. This organism rarely causes disease except in immunocompromised hosts. No other natural reservoir has ever been demonstrated, and the mode of infection is unclear. Transmission by aerosols may be possible.

A 44-year-old woman presents to the office for evaluation of skin growths on her right arm. She reports that a few weeks ago she developed some small, red bumps on her right palm, which seemed to come together into a larger nodule. This then ulcerated, but it never was painful. She has been putting topical antibiotic on this area, and it seemed to be improving. However, in the past week she has noticed new growths extending up her forearm that appear just like the original lesion. She denies having skin lesions anywhere else, denies systemic symptoms such as fever, and has no history of anything like this before. She has no significant medical history and takes no medications. She is employed as a florist and floral arranger. On examination she is comfortable appearing and has normal vital signs. On her right palm you see a circular, 1 cm diameter, ulcerated area with a surrounding red, raised border. There are two identical appearing, but smaller, lesions on the forearm. Microscopic examination of a biopsy taken from one of the lesions reveals numerous white blood cells and cigar-shaped yeast forms.

 What is the most likely infectious cause of these lesions?

 What is the most likely route by which this infection was transmitted?

 Most likely infectious etiology:Sporothrix schenckii.

 Most likely route by which this infection was transmitted: Most likely mechanism of infection is inoculation into the skin via a puncture of the hand with an infected plant (most likely a rose thorn).

Summary: A 44-year-old florist has painless, ulcerated lesions on her right hand and arm.

CLINICAL CORRELATION

Introduction

Cutaneous sporotrichosis results from the inoculation of the organism into the skin via a puncture or other minor trauma. Most cases occur in persons with occupational or avocational exposure to infected material, such as in gardening or farming. The most common exposures are to rose thorns and sphagnum moss. The initial lesions are usually in areas that are prone to trauma, such as the extremities. They are often erythematous papules or nodules, which then ulcerate. Secondary lesions develop along the lines of lymphatic drainage. The lesions are usually painless, can wax and wane, and systemic symptoms are rare. Extracutaneous infections with S. schenckii have occurred, most commonly involving the joints, particularly hand, elbow, ankle, or knees. Cases of pulmonary sporotrichosis as well as meningitis have been described. Invasive and disseminated disease may occur in the severely immunosuppressed, particularly patients with advanced HIV disease.

Cutaneous sporotrichosis is usually treated orally with either a saturated solution of potassium iodide or an antifungal agent such as itraconazole. Extracutaneous or disseminated disease is difficult to treat, but usually treated with itraconazole. Patients with concomitant HIV and sporotrichosis are usually treated prophylactically for the rest of their life with oral itraconazole.

[44.1] Which of the following fungi is most likely to cause cutaneous disease?

[44.2] A woman who pricked her finger while pruning some rose bushes develops a local pustule that progressed to an ulcer. Several nodules then developed along the local lymphatic drainage. The most reliable method to identify the etiologic agent is:

[44.1] E. Aspergillus, Cryptococcus, and Histoplasma infections routinely involve the respiratory system and form cellular components recognizable in the diagnostic laboratory. Candida species are usually endogenous flora that may be opportunistic under the right circumstances (immunocompromised patient, e.g.). Cutaneous and systemic infections are possible under these conditions. S. schenckii is typically introduced into the skin by trauma, often related to outdoor activities and/or plants. About three-fourths of the cases are lymphocutaneous, with multiple subcutaneous nodules and abscesses along the lymphatics.