What could be the cause of my persistent dry cough and significant weight loss over the past month, with no changes to my diet or exercise regimen, as an adult with an unknown medical history?

Urgent Evaluation Required: Lung Cancer Must Be Ruled Out

Your combination of persistent dry cough and unintentional weight loss is a red flag that requires immediate medical evaluation with chest imaging, as lung cancer commonly presents with these exact symptoms. 1

Why This Is Urgent

• Cough is the fourth most common presenting feature of lung cancer, and when combined with weight loss, this represents a serious warning sign that demands prompt investigation 1
• The presence of systemic symptoms like weight loss alongside chronic cough mandates direct investigation for malignancy 1
• A chest radiograph is essential as your first diagnostic step to exclude serious structural disease including lung cancer 2

Most Likely Serious Causes to Rule Out First

Lung Cancer (Highest Priority)

• Your symptom combination—dry cough plus weight loss—is classic for bronchogenic carcinoma 1
• Finger clubbing, if present on examination, together with your symptoms would strongly point toward lung cancer 1
• Even with a normal chest X-ray, further imaging with CT scan may be needed 1

Tuberculosis

• Must be considered if you live in or have traveled to endemic areas 1
• Weight loss, persistent cough, and systemic symptoms are characteristic 1

Other Serious Conditions

• Pulmonary embolism causes cough in nearly half of cases and can present with chest discomfort 3
• HIV/AIDS-related pulmonary disease if risk factors present 1

Common Benign Causes (Only After Ruling Out Cancer)

If imaging excludes malignancy and serious disease, the three most common causes of chronic dry cough in otherwise healthy adults are 1:

1. Upper Airway Cough Syndrome (33% of cases)

• Previously called post-nasal drip 1, 4
• Can present as "silent" with no other nasal symptoms 1
• Treated with first-generation antihistamine/decongestant combinations and intranasal corticosteroids 4

2. Asthma (Cough-Variant Asthma)

• 30-40% of patients with cough-variant asthma will progress to classic asthma if untreated 5
• Can occur with completely normal spirometry 2
• Requires inhaled corticosteroids even without wheezing or breathing difficulty 3, 5

3. Gastroesophageal Reflux Disease (GERD)

• Can be "silent" without heartburn symptoms 1
• Requires intensive acid suppression for at least 3 months 3

Critical Questions for Your Doctor Visit

• Are you taking an ACE inhibitor medication? (for blood pressure/heart) - These cause chronic dry cough in 5-50% of patients and must be stopped immediately 3, 2
• Do you smoke or have you recently quit? - Smoking cessation resolves cough in 90% within 4 weeks 3
• Any fever, night sweats, or hemoptysis (coughing blood)? - These are additional red flags 3, 2

What You Need Now

1. Schedule an urgent appointment with your doctor within 1-2 days for chest X-ray 1, 2
2. Do not delay - the combination of cough and weight loss requires immediate evaluation 1
3. If chest X-ray shows a mass or abnormality, expect referral for CT scan and possibly bronchoscopy 1
4. If imaging is normal, systematic evaluation for the common benign causes can proceed 1

Common Pitfall to Avoid

Do not accept reassurance or empiric treatment without imaging first. While most chronic coughs are benign, your weight loss changes the risk profile significantly and mandates ruling out cancer before treating for common causes like reflux or post-nasal drip 1, 2.