Chest Film Clinic: What caused the progressive dyspnea and cough in this tennis player?

A 38-year-old man presented to the emergency department (ED) with a 2-week history of worsening shortness of breath and dry cough. He also complained of anorexia, a 14-kg (30-lb) weight loss over 3 months, pleuritic chest pain, and night sweats.

The patient's occupational history was remarkable for a career as a professional tennis player and coach. Although previously a vigorous athlete, he reported that he could no longer perform physical activity without experiencing exertional dyspnea. His past medical history was unremarkable, including no history of tuberculosis exposure. He denied use of anabolic steroids, alcohol, or illicit drugs. He denied any homosexual activity or transfusions. The number of sexual partners in his past was unknown.

On physical examination, he was an afebrile, cachectic, ill-appearing man in moderate respiratory distress, with an elevated heart rate of 114 beats per minute and a respiratory rate of 28 breaths per minute. His oxygen saturation on room air was 90%, with improvement to 98% when 4 L/min of oxygen was administered through nasal cannula. On auscultation, decreased breath sounds were noted over the right side of the chest. There were no rales or egophony. Cardiac examination was normal except for tachycardia.

Laboratory tests on admission showed a depressed white blood cell count of 3800/mL and a low albumin level of 3.1 g/dL, as well as an elevated lactate dehydrogenase level of 425 U/L. Arterial blood gas analysis while breathing room air revealed a pH of 7.44, a PaCO₂ of 42 mm Hg, and a PaO₂ of 44 mm Hg.

Posteroanterior and lateral chest radiographs were obtained on admission (Figure 1, below).

How would you interpret these findings? How would you proceed?

Discussion on next page.

Making the diagnosis

The patient's chest radiographs demonstrate a bilateral, symmetric distribution of lung opacities, which range from a finely granular appearance in the perihilar regions to areas of alveolar consolidation in the lower lobes. Cardiac and mediastinal contours are normal, with no lymphadenopathy.

A CT scan of the chest taken 5 days after admission demonstrated bilateral diffuse ground-glass opacities, defined as areas of increased lung attenuation that do not obscure pulmonary vessels (Figure 2). A cluster of cysts was detected in the right middle lobe anteriorly.

An enzyme-linked immunosorbent assay was positive for HIV antibodies, and a follow-up Western blot confirmed the diagnosis of HIV infection. Initial plasma HIV RNA viral load was greater than 100,000 copies/mL. The CD4 count on admission was 20/µL.

Three induced sputum specimens showed the presence of Pneumocystis carinii and were negative for other organisms.

Discussion

Despite a reduced prevalence of P carinii pneumonia (PCP) because of widespread prophylaxis, PCP remains the most common life-threatening pulmonary infection in patients with AIDS and is a common AIDS-defining illness.^1-4 The mortality rate for AIDS patients during the initial stage of PCP is 10% to 20%, but the rate substantially increases with the need for mechanical ventilation.⁵ In light of the high mortality rate, it is important for clinicians and radiologists to be familiar with the characteristic clinical and radiologic manifestations of this infection.

The classic symptoms of PCP are nonproductive cough, progressive exertional dyspnea, and the insidious onset of a low-grade fever. Patients typically have symptoms for more than 7 days before presenting for medical attention. Physical examination findings include tachypnea and tachycardia, with normal findings on lung auscultation.

The classic chest radiographic feature of PCP is a bilateral perihilar or diffuse symmetric interstitial pattern, which may be finely granular, reticular, or ground-glass in appearance.^6,7 If PCP is left untreated, the parenchymal opacities may progress to airspace consolidation.⁸ CT is more sensitive and specific than chest radiography for diagnosing PCP, and thus it may be helpful when radiographic findings are negative or equivocal for this diagnosis.⁹ Indeed, chest radiographs may reveal normal findings in up to 39% of cases at the initial presentation.¹⁰ The classic CT finding in PCP is extensive ground-glass attenuation, which is often distributed in a patchy or geographic fashion with a predilection for the central, perihilar regions of the lungs.^6,8,11,12

Although PCP most often presents with the pattern of findings described above, it is important to be aware that atypical and more subtle radiographic features are emerging with increased frequency because of advances in the prophylaxis and treatment of PCP.^6-8,11 In fact, several features that were once considered unusual manifestations of PCP are now considered typical. These include cystic lung disease, spontaneous pneumothorax, and an upper lobe distribution of parenchymal opacities.⁹

Cystic lung disease is estimated to occur in one third of PCP cases.^13-15 PCP-related cysts vary in size, shape, and wall thickness.^6,14-16 The cysts are usually multiple and bilateral, and they may be located in subpleural or intraparenchymal sites.^6,8,15-17 Importantly, the cystic form of PCP is associated with an increased incidence of spontaneous pneumothorax secondary to the rupture of subpleural cysts.^8,15 Such pneumothoraces can be refractory to conventional chest tube drainage and may require pleurodesis or surgical intervention.⁸ The mortality rate is higher for patients with PCP who have pneumothoraces than for those who do not have this complication.^8,15

A definitive diagnosis of PCP requires the microscopic examination of specimens of sputum, bronchoalveolar fluid, or lung tissue for the presence of P carinii, since this organism cannot be cultured.¹⁸ An alternative, cost-effective approach for the diagnosis and treatment of PCP has been suggested. This approach calls for empiric therapy in patients who present with the classic clinical and imaging features of PCP.^8,19

The preferred treatment for PCP is trimethoprim-sulfamethoxazole (TMP-SMX). Alternative therapies include atovaquone, pentamidine, and the combination of primaquine and clindamycin. Adjuvant corticosteroid therapy to suppress lung inflammation has been shown to be of benefit in HIV-infected patients with PCP who have hypoxemia, as defined by a PaO₂ of less than 70 mm Hg or an alveolar-arterial gradient of more than 35 mm Hg while the patient is breathing room air.²⁰

Primary prophylaxis against PCP in HIV-infected patients is recommended when the CD4 count is less than 200/µL, a well-established threshold for PCP risk.⁴ TMP-SMX is the preferred prophylactic agent. For patients who have had previous episodes of PCP, secondary prophylaxis is recommended until reconstitution of the immune system with HAART, marked by an increase in CD4 count to more than 200/µL.²⁰

Bacterial infections, including infectious airway disease and pneumonia, have surpassed PCP as the most common pulmonary infections in HIV-infected patients.²¹ The clinical and imaging features of bacterial infections must be clearly distinguished from those of PCP for proper management. The typical clinical presentation of bacterial pneumonia is an acute on- set of fever and productive cough, and the symptoms usually last for less than 7 days before the patient seeks medical attention.^22,23 Radiographically, bacterial pneumonia presents as focal consolidation in either a segmental or lobar distribution.^12,24-26 Thus, the clinical and imaging features in this case are not typical of bacterial pneumonia.

The outcome in this case

In the ED, our patient was started on a regimen of TMP-SMX and prednisone for PCP. His symptoms improved significantly by hospital day 4, with oxygen saturation of 95% to 98% on room air. The patient was discharged in stable condition on a regimen of TMP-SMX, a prednisone taper, and HAART.

Within 1 week following discharge, a right pneumothorax developed as a result of cyst rupture, which was successfully treated with a small-bore chest tube. The patient will continue his PCP treatment and secondary prophylaxis until the reconstitution of his immune system. In the meantime, he will be closely monitored for AIDS-related complications.

References:

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