Differential Diagnosis
- Single most likely diagnosis
- Henoch-Schönlein purpura (HSP): This condition is characterized by the presence of diffuse ecchymoses and petechiae, particularly over the lower extremities, which matches the patient's presentation. The recent history of a viral illness also supports this diagnosis, as HSP often follows a viral infection. The laboratory findings, including a low hemoglobin level and elevated urea nitrogen, are consistent with HSP, which can involve renal and gastrointestinal manifestations.
- Other Likely diagnoses
- Hemolytic uremic syndrome (HUS): Given the patient's recent history of diarrhea, HUS is a consideration, especially with the elevated urea nitrogen and creatinine levels indicating renal involvement. However, the presence of ecchymoses and petechiae is more suggestive of HSP.
- Aplastic anemia: Although the patient has a low hemoglobin level and an elevated reticulocyte count, the presence of ecchymoses and petechiae, along with the recent viral illness, makes HSP more likely. Aplastic anemia would typically present with pancytopenia, which is not evident here.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Meningococcemia: This condition can present with petechiae and ecchymoses, but it is typically associated with a more severe and acute presentation, including fever, shock, and meningitis. Although the patient's temperature is normal, meningococcemia is a medical emergency that requires prompt recognition and treatment.
- Rare diagnoses
- Splenomegaly: While splenomegaly can be associated with various conditions that lead to bruising and petechiae (e.g., thrombocytopenia), there is no direct evidence in the provided information to support this as a primary diagnosis. Splenomegaly would typically be associated with other findings, such as hepatomegaly or specific laboratory abnormalities indicative of a underlying condition (e.g., lymphoma, leukemia).
- Other rare bleeding disorders: Conditions like thrombotic thrombocytopenic purpura (TTP) or certain coagulopathies could present with similar symptoms but are less likely given the clinical context and the absence of specific laboratory findings that would suggest these diagnoses.