Differential Diagnosis for a 17-year-old Male with Fatigue, Chills, Sore Throat, and Petechiae

The patient's symptoms, including fatigue, chills, sore throat, and the presence of petechiae on the soft palate following an unprotected sexual encounter, suggest an infectious etiology. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Acute HIV Infection: The symptoms presented, such as fatigue, chills, sore throat, and particularly the presence of petechiae, are consistent with acute retroviral syndrome, which occurs in the early stages of HIV infection. The recent history of an unprotected sexual encounter further supports this diagnosis.

• Other Likely Diagnoses

  • Infectious Mononucleosis (Mono): Caused by Epstein-Barr virus (EBV), mono can present with similar symptoms, including sore throat, fatigue, and fever. Petechiae on the palate can also be seen in EBV infection.
  • Streptococcal Pharyngitis: While primarily causing a sore throat, streptococcal infections can also lead to systemic symptoms like fever and fatigue. However, petechiae on the soft palate are less commonly associated with this condition.
  • Syphilis: Secondary syphilis can present with a wide range of symptoms, including sore throat and systemic symptoms like fatigue and fever. The rash of secondary syphilis can sometimes be accompanied by mucous membrane lesions, but petechiae are less typical.

• Do Not Miss Diagnoses

  • Meningococcemia: Although less likely given the context, meningococcemia is a life-threatening condition that can present with fever, chills, and a petechial or purpuric rash. It is crucial to consider this diagnosis due to its high mortality rate if left untreated.
  • Leptospirosis: This bacterial infection can cause a wide range of symptoms, including fever, chills, and sore throat. While less common, it is a critical diagnosis not to miss due to its potential severity and the need for prompt antibiotic treatment.
  • Disseminated Gonococcal Infection (DGI): Given the patient's recent unprotected sexual encounter, DGI is a possibility, especially if the patient has gonorrhea. DGI can cause fever, chills, and a rash, among other symptoms.

• Rare Diagnoses

  • Acute Leukemia: Certain types of leukemia can present with petechiae due to thrombocytopenia, along with systemic symptoms like fatigue and fever. However, this would be an uncommon initial presentation without other signs of bone marrow failure.
  • Aplastic Anemia: This rare condition involves bone marrow failure, which could lead to petechiae among other symptoms. However, it would typically be accompanied by more significant cytopenias and is less likely given the acute presentation and recent sexual encounter.
  • Viral Hemorrhagic Fevers: These are extremely rare in most parts of the world but can present with fever, fatigue, and a petechial rash. The recent travel history (if any) and exposure risk would make this a consideration in specific contexts.