A 7-year-old boy is brought to the emergency department due to rash, abdominal pain, and nausea. The rash first appeared 2 days ago. According to his father, a few initial red, round lesions on the back of both thighs now seem to have "merged together" and spread "all over his legs and buttocks." The rash is not itchy or painful. The abdominal pain and nausea began today and have been intermittent. The boy's appetite is decreased but he has no vomiting or diarrhea. His last bowel movement was yesterday and appeared normal. Other than an upper respiratory infection last week, the patient has been healthy and takes no medications. He went to a family barbeque last week and ate a hamburger and hot dog. Vaccinations are up to date and he has no allergies. His temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, and pulse is 105/min. On physical examination, his abdomen is soft, nondistended, and mildly tender to palpation in the periumbilical region. Skin examination shows a non-blanching purple rash on his lower extremities and buttocks. Stool guaiac is positive. Which of the following is the most likely diagnosis in this patient?

Question

A 7-year-old boy is brought to the emergency department due to rash, abdominal pain, and nausea.  The rash first appeared 2 days ago.  According to his father, a few initial red, round lesions on the back of both thighs now seem to have "merged together" and spread "all over his legs and buttocks."  The rash is not itchy or painful.  The abdominal pain and nausea began today and have been intermittent.  The boy's appetite is decreased but he has no vomiting or diarrhea.  His last bowel movement was yesterday and appeared normal.  Other than an upper respiratory infection last week, the patient has been healthy and takes no medications.  He went to a family barbeque last week and ate a hamburger and hot dog.  Vaccinations are up to date and he has no allergies.  His temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, and pulse is 105/min.  On physical examination, his abdomen is soft, nondistended, and mildly tender to palpation in the periumbilical region.  Skin examination shows a non-blanching purple rash on his lower extremities and buttocks.  Stool guaiac is positive.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfde_25b9_8f63_5d26de3960e9_MD0005_00 This patient's presentation is highly suggestive of Henoch-Schönlein purpura (HSP). HSP is primarily a pediatric vasculitis that results from systemic IgA deposition. The presentation varies in severity but most patients have a rash that begins as erythematous macules that coalesce into palpable purpura. The purpura is non-blanching and non-pruritic and is distributed symmetrically across gravity-dependent body parts (eg, legs, buttocks). Intermittent abdominal pain and nausea are usually due to small-bowel intussusception. Edema and hemorrhage in the small bowel serve as the pathological lead points. Involvement of the joints and kidneys is also common and usually manifests later. Some boys have scrotal pain/swelling. An antecedent upper respiratory infection is present in 50% of patients. HSP is diagnosed clinically, especially when the presentation is classic and involves lower-extremity purpura, as in this patient. Laboratory findings that support the diagnosis include a normal platelet count and coagulation studies and elevated inflammatory markers (eg, white blood cell count, erythrocyte sedimentation rate). Urinalysis may show casts, hematuria, pyuria, and proteinuria. HSP resolves spontaneously in most patients; some require nonsteroidal anti-inflammatory drugs or corticosteroids. (Choice A) Acute urticaria is characterized by pruritic, raised, erythematous wheals. Each lesion usually fades within 24 hours. This patient's rash is not itchy and has worsened after 24 hours, making this diagnosis unlikely. (Choice B) Hemolytic uremic syndrome consists of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure that typically occurs in patients age <5 after an acute bloody diarrheal illness. This patient has had no preceding diarrhea, making this diagnosis unlikely. (Choice D) Idiopathic thrombocytopenic purpura (ITP) presents as petechiae or purpura that develop in any skin area spontaneously or with low impact. Although it often follows a viral upper respiratory infection, the abdominal pain and extensive distribution of the purpura on this patient's legs are more consistent with HSP than ITP. (Choice E) Thrombotic thrombocytopenic purpura is a serious disorder characterized by the pentad of fever, microangiopathic hemolytic anemia (pallor), thrombocytopenia, renal failure, and neurologic impairment (eg, confusion). This patient is afebrile and neurologically intact, making this diagnosis unlikely. Educational objective: Henoch-Schönlein purpura commonly presents with purpura in gravity-dependent areas (eg, legs, buttocks) and abdominal pain from small-bowel intussusception. Arthralgias and IgA nephropathy are also common but usually manifest later. The diagnosis is based primarily on the clinical presentation. References: Clinical practice: diagnosis and management of Henoch-Schönlein purpura. (http://www.ncbi.nlm.nih.gov/pubmed/20012647) Henoch-Schönlein purpura. (http://www.ncbi.nlm.nih.gov/pubmed/19817340)

A 7-Year-Old Boy Is Brought to the Emergency Department Due