Eosinophilic pneumonia

ARDS is acute (within 1 week), bilateral, non-cardiogenic hypoxemic respiratory failure from diffuse alveolar damage, diagnosed by the 2012 Berlin criteria and graded by the Pao2/Fio2 ratio. Management is lung-protective ventilation, PEEP titration, early prone positioning for severe disease, conservative fluid strategy, and treatment of the inciting insult.

Eosinophilic granulomatosis with polyangiitis (EGPA) is the rarest antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, defined by a three-phase course of late-onset asthma and rhinosinusitis, then peripheral and tissue eosinophilia, then small- and medium-vessel vasculitis with mononeuritis multiplex. ANCA is positive in only 40 to 60 percent of patients, cardiac involvement drives most mortality, and treatment is glucocorticoids alone for non-organ-threatening disease, glucocorticoids plus cyclophosphamide or rituximab for organ-threatening disease, and mepolizumab as steroid-sparing therapy.

Strongyloides stercoralis is a soil-transmitted nematode uniquely capable of autoinfection, so it can persist for decades and, in a host started on glucocorticoids or otherwise immunosuppressed, progress to hyperinfection with gram-negative bacteremia; diagnosis is by stool larvae or serology and treatment is ivermectin.

Sarcoidosis is a multisystem granulomatous disease of unknown cause defined by noncaseating granulomas, most commonly involving the lungs and hilar lymph nodes. Most patients are asymptomatic or have a self-limited course staged by chest radiograph; symptomatic organ-threatening disease is treated with systemic glucocorticoids, with methotrexate or another steroid-sparing agent added for glucocorticoid-refractory or glucocorticoid-intolerant disease.

Idiopathic pulmonary fibrosis is a chronic, progressive fibrosing lung disease of unknown cause defined by a usual interstitial pneumonia (UIP) pattern, presenting with progressive dyspnea, dry cough, bibasilar Velcro crackles, and clubbing in older smokers. A definite UIP pattern on high-resolution CT confirms the diagnosis without biopsy; management centers on antifibrotic therapy (pirfenidone or nintedanib), oxygen, and early lung transplant referral, since corticosteroids are not indicated and median survival is 3 to 5 years.

Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.

Asthma is a chronic inflammatory airway disorder causing episodic, reversible airflow obstruction confirmed by spirometry or bronchial challenge testing. Management is a stepwise ladder led by inhaled glucocorticoids plus as-needed SABA or ICS-formoterol, escalating to biologics for severe type 2-high disease, with an oral glucocorticoid burst and frequent SABA for exacerbations.

Ascariasis is fecal-oral infection with Ascaris lumbricoides, the largest intestinal nematode, treated with albendazole 400 mg single dose; it causes Loffler pulmonary eosinophilia during larval lung migration and, with heavy adult worm burden, intestinal, biliary, or pancreatic duct obstruction.

Lymphatic filariasis is caused by the filarial nematodes Wuchereria bancrofti or Brugia malayi, transmitted by mosquito bite, producing lymphatic inflammation and obstruction that leads to lymphedema and elephantiasis, confirmed by identifying microfilariae or adult worms and treated with diethylcarbamazine.