Differential Diagnosis for a 71-year-old Female with Positive ANA and COPD Exacerbation

Single Most Likely Diagnosis

• COPD Exacerbation: The patient's symptoms of dry cough, wheezing, phlegmy tenacious sputum, and history of COPD point towards an exacerbation of her chronic condition. The positive ANA could be an incidental finding or related to a comorbid autoimmune condition, but the primary presentation suggests a COPD exacerbation.

Other Likely Diagnoses

• Infectious Pneumonia: Given the acute onset of symptoms such as cough, wheezing, and production of tenacious sputum, an infectious cause should be considered, especially in the context of a COPD exacerbation.
• Pulmonary Embolism: Although less likely, the presence of tiredness and lack of appetite could suggest a pulmonary embolism, especially if there are underlying risk factors such as immobility or recent surgery.
• Autoimmune Interstitial Lung Disease (ILD): The positive ANA raises the possibility of an autoimmune ILD, which could present with similar respiratory symptoms and could be a comorbidity in a patient with COPD.

Do Not Miss Diagnoses

• Lung Cancer: In a patient with a history of COPD and new or worsening respiratory symptoms, lung cancer must be considered due to its high prevalence in this population and the potential for similar presentations.
• Pneumonia due to Influenza or Other Viruses: Especially during flu season or in the context of a viral outbreak, these infections can precipitate severe exacerbations of COPD and have significant morbidity and mortality if not promptly treated.
• Tuberculosis (TB): Although less common, TB can present with chronic cough, weight loss, and fatigue, and is a critical diagnosis not to miss due to its public health implications and the need for specific treatment.

Rare Diagnoses

• Rheumatoid Arthritis-associated Interstitial Lung Disease: This condition is less common but could explain the positive ANA and respiratory symptoms if there are other signs of rheumatoid arthritis.
• Sjögren's Syndrome: Another autoimmune condition that could present with dry cough and positive ANA, though it is less directly linked to the primary symptoms described.
• Mixed Connective Tissue Disease: A rare autoimmune disorder that could potentially explain the positive ANA and a variety of systemic symptoms, including respiratory ones, though it would be an uncommon diagnosis in this context.