A 17-year-old boy is brought to the emergency department due to a rash and scrotal swelling. Two days ago, he developed ankle pain, followed by a rash on his legs and the tops of his feet. The lesions are not painful, but they have coalesced and darkened. Today, the patient developed a dull ache in his scrotum. He has had no fever, headache, or diarrhea. The patient has no chronic medical conditions and takes no medications. He is sexually active with 1 partner. Temperature is 36.1 C (97 F), blood pressure is 110/70 mm Hg, and pulse is 94/min. The patient is awake and alert. The neck is supple with no lymphadenopathy. Cardiopulmonary examination is unremarkable. The abdomen is soft with no rebound tenderness or guarding. The extremities have 2+ peripheral pulses. Genitourinary examination shows mild edema in the right testicle with slight tenderness to palpation, and the left testicle is normal. Both ankles are swollen. Skin examination is shown in the exhibit. Results from a complete blood count are as follows: Which of the following is the most likely diagnosis in this patient?

Question

A 17-year-old boy is brought to the emergency department due to a rash and scrotal swelling.  Two days ago, he developed ankle pain, followed by a rash on his legs and the tops of his feet.  The lesions are not painful, but they have coalesced and darkened.  Today, the patient developed a dull ache in his scrotum.  He has had no fever, headache, or diarrhea.  The patient has no chronic medical conditions and takes no medications.  He is sexually active with 1 partner.  Temperature is 36.1 C (97 F), blood pressure is 110/70 mm Hg, and pulse is 94/min.  The patient is awake and alert.  The neck is supple with no lymphadenopathy.  Cardiopulmonary examination is unremarkable.  The abdomen is soft with no rebound tenderness or guarding.  The extremities have 2+ peripheral pulses.  Genitourinary examination shows mild edema in the right testicle with slight tenderness to palpation, and the left testicle is normal.  Both ankles are swollen.  Skin examination is shown in the exhibit.  Results from a complete blood count are as follows:  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d647_5af4_bc81_adbe5a61847d_MD0003_00 This patient's ankle pain and swelling and purpuric rash on the lower extremities are concerning for Henoch-Schönlein purpura (HSP), or IgA vasculitis. HSP is a leukocytoclastic vasculitis characterized by IgA immune complex deposition within small vessels. The classic tetrad of clinical manifestations includes the following: Henoch-Schönlein purpura (HSP) Lower extremity palpable purpura Lower extremity arthralgia/arthritis (eg, ankle pain) Abdominal pain (or occult gastrointestinal bleeding, which can result in anemia) Renal disease (eg, hematuria) Clinical findings can appear in any order and may not all be seen at initial presentation. Purpura is the most common initial manifestation and is not associated with thrombocytopenia or coagulopathy. The rash typically coalesces and darkens over days. In addition to classic symptoms, up to one-third of boys with HSP have unilateral or bilateral scrotal pain and swelling, as seen in this patient, due to localized vasculitis. Blood flow to the testicles is normal or increased, and scrotal symptoms typically self-resolve. (Choice A) Acute parvovirus infection is associated with joint pain and swelling, particularly in women. However, in contrast to this patient's purpuric lesions, erythematous cheeks and a lacy, reticular rash on the trunk and extremities are classic for parvovirus. erythematous cheeks (Choice B) Chlamydia trachomatis is a sexually transmitted infection that can cause unilateral scrotal pain and edema due to epididymitis, as well as joint swelling due to reactive arthritis. However, arthritis is typically asymmetric (most commonly involving the knees), and C trachomatis does not cause a purpuric rash as seen in this patient. (Choice D) Rocky Mountain spotted fever is a tickborne disease that can cause myalgia and arthralgia with a petechial rash that begins on the wrists and ankles and often involves the palms and soles. However, patients are typically ill-appearing with fever, headache, and thrombocytopenia (none of which are seen in this patient), and scrotal involvement does not occur. (Choice E) Although secondary syphilis can include arthritis/arthralgia and rash, the classic dermatologic finding is a scaly, papular rash involving the palms and soles. Genital examination may reveal condylomata lata (ie, raised, gray/white lesions) or a healing chancre (ie, painless ulcer seen with primary syphilis), but isolated scrotal edema would not be expected. scaly, papular rash Educational objective: The classic tetrad of findings seen with Henoch-Schönlein purpura (IgA vasculitis) includes lower extremity palpable purpura, arthralgia/arthritis, abdominal pain, and/or renal disease. The vasculitis can also involve the scrotum, causing scrotal pain and swelling. References: Unusual presentation of Henoch-Schönlein purpura. (http://www.ncbi.nlm.nih.gov/pubmed/29848517)

A 17-Year-Old Boy Is Brought to the Emergency Department Due