Past is Prologue

A 56-year-old Japanese man with a history of renal transplantation 20 years prior presented to the emergency department (ED) with two months of dyspnea on exertion and one day of fever and chills. The patient was in his usual state of health until two months prior to presentation, when he gradually noticed shortness of breath after sustained or effortful physical activities. The dyspnea improved with rest. Over the following two months, he noticed that the shortness of breath came on with lesser degrees of exertion, such as walking 100 meters. One day before presentation, he developed a fever of 39°C and chills at home, which prompted him to seek ED care. He denied chest pain, cough, leg swelling, or paroxysmal nocturnal dyspnea.

The differential diagnosis of exertional dyspnea progressing over several months includes cardiac, pulmonary, hematologic, and neuromuscular conditions. The patient’s history of renal transplantation prompts consideration of worsening indolent pneumonia (eg, Aspergillus, cytomegalovirus [CMV], or Pneumocystis pneumonia), allograft dysfunction with volume overload, recrudescence of the underlying disease that incited renal failure earlier in life (eg, vasculitis), or a late-onset posttransplantation lymphoproliferative disorder (PTLD). Additionally, acute fever in an immunocompromised patient immediately raises suspicion for infection (eg, pneumonia, enteritis, or urinary tract infection). At this point, it is difficult to know whether the subacute-to-chronic exertional dyspnea and the acute fever are consequences of the same disease or separate, potentially overlapping, processes.

His past medical history was significant for end-stage renal disease due to membranoproliferative glomerular nephropathy (MPGN), for which living, related-donor kidney transplantation was performed 20 years earlier. He also had type 2 diabetes mellitus, hypertension, and basal cell carcinoma of the face, which had been resected three years prior without spread or recurrence. He had no known allergies. Medications included prednisolone 15 mg daily, azathioprine 100 mg daily, and cyclosporine 100 mg daily, as well as amlodipine and candesartan. He lived in Japan with his wife and children. He denied any animal or environmental exposures. He did not smoke cigarettes or drink alcohol and had not traveled recently. His father had diabetes mellitus.

Recrudescence of an underlying autoimmune condition that may have incited MPGN earlier in life is unlikely while taking an immunosuppressive regimen consisting of prednisolone, azathioprine, and cyclosporine. However, these medications do increase susceptibility to infections, lymphoma, and skin cancers. Though he is immunocompromised, the patient is not on prophylaxis for Pneumocystis pneumonia (PCP). PCP in HIV-negative patients is associated with recent glucocorticoid exposure and typically follows an acute-to-subacute course with hypoxemia and respiratory distress. Though the risk of PCP infection is considered highest in the early posttransplantation period (when immunosuppression is most intense), many cases are diagnosed years after transplantation among patients no longer on prophylaxis. The patient has type 2 diabetes mellitus and hypertension, which are known complications of calcineurin inhibitor and steroid therapy and increase the risk of cardiovascular disease. Cardiovascular disease is a major cause of death among renal transplant recipients. Exertional dyspnea may be the presenting symptom of coronary artery disease.

On physical examination, the patient was alert, oriented, and in no acute distress. His temperature was 38.5°C, blood pressure 120/60 mm Hg, heart rate 146 beats per minute, respiratory rate 18 breaths per minute, and oxygen saturation 93% while breathing ambient air. The conjunctiva were normal without pallor or icterus. There was no cervical lymphadenopathy. Cardiac examination revealed tachycardia with a regular rhythm, normal S1 and S2, and no murmurs, rubs, or gallops. Jugular venous pressure was not elevated, and there was no lower extremity edema. Lungs were clear to auscultation bilaterally. The abdomen was soft, nontender, and nondistended. There was no tenderness over the transplanted kidney and no hepatosplenomegaly.

Dyspnea, fever, and tachycardia may be the sole manifestations of pneumonia in solid organ transplant recipients. The absence of cough or adventitious breath sounds does not eliminate concern for pneumonia. Pathogens that cause indolent pneumonia in immunocompromised patients include viruses (such as typical respiratory viruses and CMV), bacteria (typical organisms, Nocardia, Rhodococcus), and mycobacteria. Fungal causes include Aspergillus, Candida, Cryptococcus, Pneumocystis, and endemic mycoses. A detailed environmental history should be taken, and providers should ascertain which fungal diseases are endemic in the patient’s region of residence. There are no examination features suggesting hypervolemia or anemia. Although there is no hepatosplenomegaly or lymphadenopathy, PTLD often involves extranodal tissues, including the lungs. The incidence of PTLD is highest in the 12 months following transplantation, but it may occur at any time in the posttransplantation course. A complete blood count, comprehensive metabolic panel, lactate dehydrogenase (LDH), and blood and sputum cultures are indicated, along with computed tomography (CT) of the chest.

The leukocyte count was 3,500 cells/mm³, the hemoglobin level 9.0 g/dL, mean corpuscular volume 102 fL, and the platelet count 137,000 cells/mm³. The sodium level was 130 mEq/L, potassium 4.6 mEq/L, blood urea nitrogen 41 mg/dL, and creatinine 3.5 mg/dL. These complete blood count and serum electrolyte results were unchanged from the patient’s baseline values. The serum LDH level was 1,895 IU/L (normal range, 115-245 IU/L). The serum ferritin was 2,114 ng/mL (normal range, 13-277 ng/mL). A chest radiograph revealed diffuse, airspace-filling opacities in the bilateral lung bases. The urinalysis was normal. The patient was admitted and started empirically on intravenous ceftriaxone for potential bacterial pneumonia.

Chronic pancytopenia may result from azathioprine or cyclosporine use, marrow suppression or infiltration by a multisystem disease, or nutritional deficiency. Hemophagocytic lymphohistiocytosis (HLH) triggered by infection, a rheumatologic condition, acquired immunodeficiency, or malignancy can present with fevers, pancytopenia, and elevated ferritin, while splenomegaly may be absent. The euvolemic state, baseline creatinine level, and normal urinalysis argue against allograft dysfunction. The elevated serum ferritin nonspecifically confirms systemic inflammation. LDH, an intracellular enzyme involved in the bidirectional conversion of lactate to pyruvate, is expressed across tissue types. Elevated serum LDH attests to cell destruction, in this case potentially from lung infection (such as PCP) or malignancy (such as PTLD). At this point, the differential diagnosis of fever and pulmonary infiltrates in this patient remains broad.

Azathioprine and cyclosporine were stopped. The patient remained febrile despite the administration of intravenous antibiotics. His hypoxia worsened with an oxygen saturation of 90%-93% on 5 L/min of supplemental oxygen administered by nasal cannula. Noncontrast chest CT obtained on the second hospital day revealed ground-glass opacities in the bilateral lung bases. Blood, sputum, and urine cultures were sterile. As empiric therapies, ganciclovir was started for CMV infection, ciprofloxacin added for atypical pneumonia, and trimethoprim-sulfamethoxazole added for Pneumocystis infection.

These chest imaging findings help prioritize the differential diagnosis. Bibasilar ground-glass opacities are evident, while pulmonary masses, nodules, cavitation, adenopathy, and pleural effusions are absent. The differential diagnosis of multifocal ground-glass opacities on chest imaging includes infectious pneumonia, chronic interstitial lung disease, acute alveolar conditions (eg, cardiogenic pulmonary edema, acute respiratory distress syndrome, diffuse alveolar hemorrhage), or other pathologies (eg, drug toxicity, bronchoalveolar carcinoma, cryptogenic organizing pneumonia).