Differential Diagnosis for Nonblanching, Petechial Rash

• Single Most Likely Diagnosis
  • Idiopathic Thrombocytopenic Purpura (ITP): This condition is characterized by low platelet count, leading to petechiae, purpura, and other bleeding manifestations. The nonblanching, petechial rash is a hallmark of ITP, making it the most likely diagnosis.
• Other Likely Diagnoses
  • Viral Infections (e.g., Mononucleosis, CMV): Certain viral infections can cause a petechial rash, often accompanied by other symptoms like fever, sore throat, and lymphadenopathy.
  • Medication-Induced Thrombocytopenia: Various medications, such as heparin, aspirin, and certain antibiotics, can induce thrombocytopenia, resulting in a nonblanching, petechial rash.
  • Vasculitis (e.g., Henoch-Schönlein Purpura): Vasculitis can cause a petechial rash, often with other symptoms like joint pain, abdominal pain, and renal involvement.
• Do Not Miss Diagnoses
  • Meningococcemia: This life-threatening condition, caused by Neisseria meningitidis, can present with a nonblanching, petechial rash, often accompanied by fever, headache, and neck stiffness. Prompt recognition and treatment are crucial to prevent severe morbidity and mortality.
  • Disseminated Intravascular Coagulation (DIC): DIC can cause a petechial rash, along with other symptoms like bleeding, thrombosis, and organ dysfunction. Early diagnosis and treatment are essential to prevent severe complications.
  • Thrombotic Thrombocytopenic Purpura (TTP): TTP is a rare but life-threatening condition characterized by thrombocytopenia, microangiopathic hemolytic anemia, and renal failure. A nonblanching, petechial rash can be a presenting feature, and prompt recognition is critical to initiate timely treatment.
• Rare Diagnoses
  • Ehlers-Danlos Syndrome: This genetic disorder can cause easy bruising and a petechial rash due to fragile blood vessels and poor wound healing.
  • Scurvy: Vitamin C deficiency can lead to a petechial rash, along with other symptoms like fatigue, malaise, and joint pain.
  • Amyloidosis: Rarely, amyloidosis can cause a petechial rash, often accompanied by other symptoms like weight loss, fatigue, and organ dysfunction.