Pneumocystis jiroveci (formerly Pneumocystis carinii), the pneumocystis species that affects humans, is a fungal organism known to cause life-threatening pneumonia in immunocompromised patients. Studies performed in immunosuppressed animals indicate that an immune defect of T cell function is a prerequisite for the initiation of an infection. Although symptomatic Pneumocystis jiroveci pneumonia (PCP) is rare in the immunocompetent patients, evidence indicates that seroconversion has occurred in most persons by a young age. This implies that subclinical infection is common and that both de novo infection and reactivation of latent infection are important factors in the pathogenesis of PCP.
The patient is a 40-year-old man with a long standing history of cocaine, tobacco and alcohol abuse who presented with a non-productive cough, progressively worsening shortness of breath and dyspnea on exertion of 3 weeks duration. He reported having unprotected sex with multiple partners. Physical examination revealed a well-nourished tachypneic male with crackles over the right lower lobe, regular heart sounds, with absence of pedal edema and no jugular venous distension. Chest X-ray showed cardiomegaly with diffusely increased interstitial markings with bullous changes in the right upper lobe. ABG on 50% FiO2 showed a PaO2 of 63 mmHg. Urine toxicology was positive for cocaine. Echocardiogram demonstrated a dilated LV with reduced ejection fraction. Patient was started on heart failure treatment, which failed to relieve his symptoms. Due to his risk factors for HIV, a diagnosis of PCP was entertained. Subsequently the patient was started on trimethoprim-sulfamethoxazole and prednisone resulting in rapid clinical improvement. His HIV test was negative and his CD4 count was more than 700 cells/μL on two separate occasions. BAL with silver stain was positive for P jiroveci confirming the diagnosis of PCP. Surprisingly however the LDH was only 157 units/L.
The relative risk of infection with Pneumocystis is predictable in most hosts in which this infection occurs. Though P jiroveci DNA has been detected by polymerase chain reaction (PCR) in the general population, definitive diagnosis of PCP depends on the identification of characteristic organisms seen on examination of pulmonary specimens. Though at risk for immunosupression, our patient was noted to be HIV negative on two separate occasions with a normal CD4 cell count. BAL taken from our patient demonstrated P jiroveci cysts consistent with the clinical presentation of marked hypoxemia, dyspnea and cough out of proportion to physical or radiological findings with no evidence of congenital, induced or acquired immunosupression. His rapid and complete response to trimethoprim-sulfamethoxazole and prednisone further support the diagnosis of PCP.
Our case demonstrates an unusual presentation of PCP in light of the patient’s immune status. This case may represent a rare manifestation of PCP in an immunocompetent individual, or suggest an immunodeficiency state not recognizable by measurement of merely the CD4 count.
J.B. Damian, None.