Differential Diagnosis for a 67-year-old Male with Persistent Cough
Single Most Likely Diagnosis
- Lisinopril-induced cough: The patient is taking lisinopril for hypertension, and a dry cough is a well-known side effect of ACE inhibitors like lisinopril. The patient's reluctance to change medications due to concerns about identifying new pills because of visual impairment suggests that the cough may be related to his current medication regimen.
Other Likely Diagnoses
- Chronic heart failure: The elevated BNP (brain natriuretic peptide) suggests that the patient may have some degree of heart failure, which can cause a chronic cough.
- Chronic obstructive pulmonary disease (COPD): Although the patient denies congestion or mucus production, COPD can cause a dry cough, especially in older adults with a history of smoking (although not mentioned in the patient's history).
- Gastroesophageal reflux disease (GERD): GERD can cause a dry cough, especially if the patient has symptoms at night or when lying down.
Do Not Miss Diagnoses
- Pulmonary embolism: Although less likely, a pulmonary embolism can cause a sudden onset of cough and can be life-threatening if not diagnosed promptly. The patient's elevated BNP could also be indicative of a pulmonary embolism.
- Lung cancer: The patient's age and persistent cough warrant consideration of lung cancer, especially if the cough is localized to one area or if there are other symptoms like weight loss or hemoptysis.
- Tuberculosis: Although less common, tuberculosis can cause a chronic cough and should be considered, especially if the patient has been exposed to someone with TB or has traveled to an area with high TB prevalence.
Rare Diagnoses
- Sarcoidosis: A rare condition that can cause a dry cough, sarcoidosis is characterized by granulomatous inflammation in various organs, including the lungs.
- Interstitial lung disease: A group of rare conditions that can cause a dry cough, interstitial lung disease includes conditions like idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia.
- Toenail fungus with systemic involvement: Although the black spot on the toenail is likely a fungal infection, in rare cases, fungal infections can disseminate and cause systemic symptoms, including a cough. However, this is extremely unlikely and would require other systemic symptoms to be considered.