Severe Pneumonia: Given the symptoms of fever, fatigue, shortness of breath, and the physical exam findings, severe pneumonia is a leading consideration. The elevated liver enzymes (AST and ALT) could be due to systemic infection or sepsis, and thrombocytopenia with large platelets can be seen in severe infections affecting the bone marrow or due to a consumptive coagulopathy.

Sepsis of Non-pulmonary Origin: Although the respiratory symptoms are prominent, the presence of fever, fatigue, elevated liver enzymes, and thrombocytopenia could also suggest sepsis from a non-pulmonary source, such as a urinary tract infection or intra-abdominal infection, with secondary effects on the lungs.
Acute Respiratory Distress Syndrome (ARDS): Given the shortness of breath and diminished lung sounds without adventitious sounds, ARDS could be a consideration, especially if there's an underlying cause such as severe pneumonia, sepsis, or another systemic insult.
Viral Hemorrhagic Fever or Severe Viral Infection: The combination of fever, thrombocytopenia, and elevated liver enzymes could suggest a viral hemorrhagic fever or a severe viral infection, although this would be less common and dependent on exposure history.

Pulmonary Embolism: Although the presentation is more suggestive of an infectious or inflammatory process, pulmonary embolism can cause sudden onset of shortness of breath and can be associated with fever and thrombocytopenia in some cases. It's crucial not to miss this diagnosis due to its high mortality if untreated.
Endocarditis: Infective endocarditis can present with fever, fatigue, and embolic phenomena, including pulmonary emboli or septic emboli to the lungs, which could explain some of the symptoms and lab findings.
Meningitis or Encephalitis: Although less directly related to the respiratory symptoms, these conditions can cause fever, altered mental status (which might be perceived as fatigue), and can have systemic effects including thrombocytopenia and elevated liver enzymes.

Ehrlichiosis or Anaplasmosis: These tick-borne illnesses can cause fever, fatigue, thrombocytopenia, and elevated liver enzymes, and although they are less common, they should be considered in the appropriate epidemiological context.
Hantavirus Pulmonary Syndrome: This rare viral infection can cause severe respiratory symptoms, including shortness of breath, and is associated with thrombocytopenia and elevated liver enzymes, but it is highly dependent on specific exposure risks.
Leptospirosis: Another rare infection that can cause a wide range of symptoms including fever, fatigue, respiratory symptoms, and liver enzyme elevation, along with thrombocytopenia, but it typically requires specific exposure to contaminated water.