Differential Diagnosis

The patient presents with a complex array of symptoms including headaches, fevers, loose bowel motions, dry cough with haemoptysis, chest pain, and several other systemic complaints. Given the information, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Infectious Mononucleosis (Mono): Justification - The combination of sore throat, fever, fatigue (implied by arm and shoulder weakness), and the presence of a swollen and erythematous tonsil without pus, along with systemic symptoms like headaches and photophobia, points towards infectious mononucleosis. The recent onset and the constellation of symptoms are consistent with this diagnosis.
• Other Likely Diagnoses
  • Tuberculosis (TB): Justification - Although less common in a 19-year-old without specific risk factors, the presence of dry cough, haemoptysis, and systemic symptoms like fevers and night sweats (implied by episodes of feeling very hot then very cold) could suggest TB, especially if the patient has been exposed or has risk factors not mentioned.
  • Influenza or Other Viral Respiratory Infections: Justification - The initial symptoms of runny nose, fever, and dry cough could suggest a viral respiratory infection. However, the progression to haemoptysis and the severity of systemic symptoms might indicate a more severe or complicated infection.
  • Pneumonia: Justification - Despite clear chest auscultation, the presence of chest pain with coughing, dry cough, and haemoptysis could indicate pneumonia, particularly if it's an atypical or early presentation.
• Do Not Miss Diagnoses
  • Lung Cancer: Justification - Although extremely rare in a 19-year-old, any case of haemoptysis warrants consideration of lung cancer, especially with a history of vaping.
  • Pulmonary Embolism: Justification - Sudden onset of chest pain and shortness of breath (implied by SOB when cold) could suggest a pulmonary embolism, which is a medical emergency.
  • Meningitis: Justification - The combination of headache, fever, photophobia, and blurred vision could indicate meningitis, a potentially life-threatening condition requiring immediate attention.
• Rare Diagnoses
  • Wegener's Granulomatosis (Granulomatosis with Polyangiitis): Justification - This rare autoimmune disorder can present with a combination of respiratory and systemic symptoms, including haemoptysis and fever, but it would be an unusual diagnosis in this age group without other specific findings.
  • Sarcoidosis: Justification - Although rare, sarcoidosis can present with pulmonary symptoms, fever, and systemic complaints. However, it typically has a more chronic course and might include other findings like skin or eye involvement.

Each of these diagnoses requires careful consideration of the patient's symptoms, history, and the results of investigations like the throat swab and potentially further tests such as chest imaging or blood work to confirm or rule out these conditions.