Differential Diagnosis for Prominent Interstitial Markings in Both Lungs

Single Most Likely Diagnosis

• Pulmonary Edema: This condition is characterized by the accumulation of fluid in the lungs due to various causes such as heart failure, high altitude, or fluid overload. It often presents with prominent interstitial markings on chest radiographs due to the interstitial edema.

Other Likely Diagnoses

• Chronic Interstitial Lung Disease (ILD): Conditions like idiopathic pulmonary fibrosis, sarcoidosis, and lymphangitic carcinomatosis can cause prominent interstitial markings. These diseases lead to inflammation and fibrosis of the lung interstitium.
• Infectious Diseases: Certain infections such as viral pneumonia (e.g., COVID-19), mycoplasma pneumonia, and pneumocystis jirovecii pneumonia can present with interstitial infiltrates.
• Smoking-Related Lung Disease: Chronic obstructive pulmonary disease (COPD) and other smoking-related conditions can lead to changes in lung architecture, including prominent interstitial markings.

Do Not Miss Diagnoses

• Pulmonary Embolism: Although not typically the first diagnosis that comes to mind with interstitial markings, pulmonary embolism can cause subtle interstitial changes, especially if there are associated small infarctions or hemorrhages. Missing this diagnosis can be fatal.
• Lymphangitic Carcinomatosis: This condition, characterized by the spread of cancer to the lymphatic vessels of the lungs, can present with prominent interstitial markings and is critical not to miss due to its implications for cancer staging and treatment.

Rare Diagnoses

• Lymphoid Interstitial Pneumonia (LIP): A rare condition characterized by infiltration of the lung interstitium by lymphoid cells, often associated with autoimmune disorders or immunodeficiency states.
• Alveolar Microlithiasis: A rare disease where small calculi form within the alveoli, leading to interstitial patterns on imaging.
• Pulmonary Alveolar Proteinosis: A rare condition characterized by the accumulation of surfactant-like protein and phospholipids in the alveoli, leading to interstitial changes on chest radiographs.

Each of these diagnoses has distinct clinical and radiological features, and a thorough diagnostic workup, including clinical history, laboratory tests, and possibly high-resolution CT scans, is necessary to differentiate among them.