Pneumonia / Resp infections / arteritis

Question 1

Eosinophilic pneumonia

Answer 1

Description:

• rare disease. Characterized by rapid eosinophilic infiltration of the pulmonary parenchyma / interstitium. Acute hypersensitivity response to an unidentified inhaled allergen

Pathophys:

• The cause of acute eosinophilic pneumonia (AEP) remains unknown.
• Some investigators have suggested that AEP is an acute hypersensitivity reaction to an unidentified inhaled antigen in an otherwise healthy individual (esp occurs in pts who resume smoking after period of cessation, water pipe THC smokers)
• Associated drugs inc: cocaine, daptomycin, gemcitabine, infliximab, ranitidine, sulfasalazine/mesalamine, venlafaxine
• other associations: previous irradiation of the chest, or travel or residence in an area with an increased likelihood of exposure to endemic parasites or fungi

Epidem:

• mostly affects pts 20-40yo
• men > women

Clinical features:

• acute illness often <1wk (but can be 1-4wks)
• Nonproductive cough (95%), dyspnea (92 percent), and fever (88% pts, often high fever) are present in almost every patient. Bibasilar inspiratory crackles and occasionally rhonchi on forced exhalation are heard upon auscultation of the chest. 63% pts in one study developed respiratory failure and required mechanical ventilation.
• Associated symptoms and signs can include malaise, myalgias, night sweats, chills, and pleuritic chest pain
• AEP can rapidly progress to acute respiratory failure. Approximately two-thirds of individuals may require mechanical ventilation.
• *Labs**:
• Patients generally present with an initial neutrophilic leukocytosis
• patients do not typically have peripheral blood eosinophilia at the time of presentation (this is moreso in chronic eosinophilic pneumonia). In most cases, the eosinophil fraction is not elevated initially, but may become markedly elevated during the subsequent course. The level of eosinophilia returns to normal when the illness resolves.
• Elevated ESR, CRP, high IgE
• sputum eosinophilia

Radiology:

• CXR (acute eosinophilic pneumonia): subtle reticular or ground glass opacities, often with Kerley B lines. As the disease progresses, bilateral diffuse mixed ground glass and reticular opacities develop. Small pleural effusions are common (noted in up to 70% of patients) and are frequently bilateral
• HRCT (AEP): characterized by bilateral, random, and patchy ground-glass or reticular opacities. Centrilobular nodules are seen in 50% cases, air-space consolidation is seen in 40% cases
• Chronic eosinophilic pn: the opacities are typically localized to the lung periphery.

Diagnostic criteria:

●A febrile illness of short duration (one month or less, but often less than one week)

●Hypoxemic respiratory failure (eg, pulse oxygen saturation [SpO2] <90 percent on room air or arterial oxygen tension [PaO2] <60 mmHg)

●Diffuse pulmonary opacities on chest radiograph

●BAL differential cell count showing eosinophilia >25%

●Absence of known causes of eosinophilic pneumonia, including drugs, infections, asthma, or atopic disease

DDx:

• ANCA test to investigate for granulomatosis with polyangiitis (Wegener’s) or eosinophilic granulomatosis with polyangiitis (EGPA, Churg Strauss)
• Coccidiodes (test IgM and IgG serology)
• Strongyloides, paragonimiasis
• infection, haemorrhage, malignancy (should send off MCS, cell count, cytology with BAL).

Treatment:

• Initial management of acute eosinophilic pneumonia (AEP) usually includes supportive care with supplemental oxygen and possibly mechanical ventilation, empiric antibiotics until culture results are available, and systemic glucocorticoid therapy.
• If not improving with antibiotics (prior to formal diagnosis), should give IV glucocorticoids. Patients with AEP improve rapidly (within 12 to 48 hours) in response to intravenous )methylpred 60-125mg QID) or oral glucocorticoid therapy (pred 40-60mg daily).
• continue oral pred for 2wks after symptoms and CXR findings completely resolve. If rapid improvement, can taper dose over 1-2wks. If slow to improve, provide a slow wean (taper dose by 5mg every 7days until complete cessation, usu up to 4wks).