Differential Diagnosis for Nonblanching Rash
- Single most likely diagnosis
- Senile Purpura: This condition is common in elderly individuals and is characterized by nonblanching, petechial rashes, typically on the lower extremities. The lack of systemic symptoms and the absence of new medications make this a plausible diagnosis. The itching sensation could be secondary to the skin's reaction.
- Other Likely diagnoses
- Vasculitis: Although less common, vasculitis could present with a nonblanching rash and itching. The absence of systemic symptoms like headache and the specific localization to the lower extremities might lean away from this, but it remains a consideration.
- Thrombocytopenia: A low platelet count could lead to petechiae. The patient's age and the absence of other symptoms like easy bruising or bleeding might make this less likely, but it's still a possibility, especially if there's an underlying condition affecting platelet count.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Disseminated Intravascular Coagulation (DIC): Although rare and typically associated with more severe systemic symptoms, DIC can present with petechiae and could be life-threatening if not recognized and treated promptly.
- Meningococcemia: Despite the absence of headache, this condition can rapidly progress and is fatal if not treated immediately. The rash in meningococcemia can initially appear as nonblanching petechiae.
- Rare diagnoses
- Amyloidosis: Cutaneous amyloidosis can present with petechiae, but it's rare and usually associated with other systemic or cutaneous manifestations.
- Scurvy: Vitamin C deficiency can lead to perifollicular petechiae and other skin manifestations. Given the patient's age and potential for poor nutrition, this could be considered, although it's less likely without other symptoms like malaise or joint pain.