Pneumocystis carinii Pneumonia Presenting as an Isolated Pulmonary Nodule in a Non-HIV-Infected Immunosuppressed Patient

Abstract

Case Report. A 68-year-old male with stage 4A Mantel cell lymphoma diagnosed six months previously was evaluated for his seventh cycle of chemotherapy (Cytoxan, doxorubicin, vincristine, and rituxan, alternating with methotrexate and Ara-C). The prior cycle of chemotherapy was complicated by a 10-day episode of neutropenia without fever. At this evaluation, the patient had no complaints, but chest roentgenography showed a left-lower-lung-field nodule that was not present on a roentgenograph two weeks previously or a CT scan 10 weeks previously. Physical examination findings were unremarkable; temperature and lung findings were normal. CT of the chest confirmed a 1.0 × 1.8–cm nodule in the lower lobe of the left lung (Figure 1). A PET scan did not demonstrate increased signals from the lungs. CT-guided aspiration of the lung lesion was performed. A biopsy specimen from the nodule was described as a “frothy, honey-combed material in macrophages,” and a silver stain confirmed the presence of Pneumocystis carinii (Figure 2). The patient was treated with a three-week course of oral trimethoprim/sulfamethoxazole (160/800 mg; two tablets three times a day) and received his scheduled chemotherapy. One month later, chest CT demonstrated resolution of the nodule.FIGURE 1.: CT of chest, showing a nodule (1 × 1.8 cm) in the lower lobe of the left lung.FIGURE 2.: A lung biopsy showed giant cells (original magnification, × 250). The same area is enlarged in the upper left corner (original magnification, × 1000; both stained with hematoxylin–eosin). Lower left corner shows Pneumocystis (silver stain; original magnification, × 1000).Discussion. Pulmonary nodules in the immunocompromised host have a wide array of causes. Malignancy is a common cause, and a relapse of Mantel cell lymphoma or a second malignancy needed to be considered in this case. Infectious agents known to cause isolated pulmonary nodules include fungi such as Aspergillus, Mucor, Cryptococcus, Sporothrix, Histoplasma, Blastomyces, and Coccidioidomyces species, as well as bacteria such as Nocardia, Rhodococcus, Legionella, or Mycobacterium. It is unusual for Pneumocystis carinii to be the causative agent of an isolated nodule, and it was recognized as the cause only after fine-needle aspiration and microscopic identification. For this immunosuppressed patient, treatment was considered warranted because of the risk for the local process to spread. This case underlines the importance of a thorough workup of a new pulmonary nodule in such a setting. Pneumocystis carinii pneumonia (PCP) typically presents with bilateral interstitial infiltrates, but many other roentgenographic presentations have been described, including normal chest roentgenographic findings [1]. Atypical presentations of PCP have been associated with inhaled pentamidine prophylaxis. The incidence of upper-lobe disease, cysts, and spontaneous pneumothorax are increased in patients receiving such prophylaxis. Pneumocystis carinii has been rarely reported to cause pulmonary nodules [2]. In a prior case study, two of 150 HIV-infected patients with PCP presented with a solitary pulmonary nodule [3]. In a separate study of isolated pulmonary nodules in HIV-infected patients, one of 10 was determined to be due to Pneumocystis [4]. In non-HIV-infected patients this presentation of PCP is rare, and so far it has been reported to occur in only one pediatric patient [5] and one adult heart transplant recipient [6]. Although isolated pulmonary nodules are a common complication in transplantation patients, large case reviews have not revealed Pneumocystis as a cause [7,8]. A review of the literature and MEDLINE uncovered no other case report of an isolated pulmonary nodule due to Pneumocystis in a patient receiving chemotherapy. We have histopathologically confirmed Pneumocystis as the cause of a solitary pulmonary nodule in such a patient.