A 33-year-old man with no prior medical history comes to the emergency department due to abdominal discomfort that began 24 hours ago. He describes the discomfort as a dull ache in his abdomen that is accompanied by nausea and malaise. Approximately 3 weeks ago, he abruptly developed pain in his hands, ankles, and knees. This was quickly followed by a pruritic rash that initially involved only his lower abdomen but then spread to his entire trunk and extremities. He also had low-grade fevers over the same period. He has had no recent travel or insect bites but reports using intravenous heroin over the last year. Temperature is 38.3 C (100.9 F), blood pressure is 120/70 mm Hg, pulse is 92/min, and respirations are 14/min. Examination shows moist mucous membranes and poor dentition with no lesions in the oropharynx. Lung fields are clear with normal S1 and S2. The abdomen is soft and mildly tender in the right upper quadrant with a palpable liver 3 cm below the costal margin. The joints of his hands, ankles, and knees are diffusely tender to palpation but without erythema or edema. Scattered skin lesions that are raised, erythematous, and well-defined are noted over his trunk and extremities. Laboratory results are as follows: Which of the following has the most similar pathophysiological mechanism to that of this patient's current condition?

Question

A 33-year-old man with no prior medical history comes to the emergency department due to abdominal discomfort that began 24 hours ago.  He describes the discomfort as a dull ache in his abdomen that is accompanied by nausea and malaise.  Approximately 3 weeks ago, he abruptly developed pain in his hands, ankles, and knees.  This was quickly followed by a pruritic rash that initially involved only his lower abdomen but then spread to his entire trunk and extremities.  He also had low-grade fevers over the same period.  He has had no recent travel or insect bites but reports using intravenous heroin over the last year.  Temperature is 38.3 C (100.9 F), blood pressure is 120/70 mm Hg, pulse is 92/min, and respirations are 14/min.  Examination shows moist mucous membranes and poor dentition with no lesions in the oropharynx.  Lung fields are clear with normal S1 and S2.  The abdomen is soft and mildly tender in the right upper quadrant with a palpable liver 3 cm below the costal margin.  The joints of his hands, ankles, and knees are diffusely tender to palpation but without erythema or edema.  Scattered skin lesions that are raised, erythematous, and well-defined are noted over his trunk and extremities.  Laboratory results are as follows:  Which of the following has the most similar pathophysiological mechanism to that of this patient's current condition?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c171_e4bc_8f63_9fc42f981e73_MD0005_00 Serum sickness (SS) is an immune complex-mediated hypersensitivity reaction (type III) that occurs when circulating antibodies combine with antigen (classically heterologous proteins such as equine proteins) in blood and tissues and overload normal clearance mechanisms. This then activates complement and causes disease. This patient with recent intravenous drug use has likely contracted hepatitis B infection. A minority of patients with acute hepatitis B infection develop an SS-like syndrome that is attributed to complement activation by circulating immune complexes composed of hepatitis B surface antigen. It is characterized by fever, polyarthritis, and dermatitis. Patients also frequently report fatigue or malaise. The rash of the illness is variable and can include urticaria, as seen in this patient, or several other patterns (eg, maculopapular, petechial). SS-like syndrome usually develops during the prodromal, preicteric phase of acute infection and resolves with the onset of jaundice. Other extrahepatic manifestations of hepatitis B infection explained by circulating immune complexes include polyarteritis nodosa and glomerulonephritis (usually membrane nephropathy and less often membranoproliferative glomerulonephritis). (Choice A) Anaphylaxis classically involves an IgE-mediated immediate hypersensitivity reaction (type I). Urticarial rash occurs but arthralgias are not typical. (Choice B) Autoimmune hemolytic anemia occurs when circulating cytotoxic autoantibodies (type II reaction) are directed against the patient's own red blood cells. Patients typically have symptoms of anemia (eg, dyspnea on exertion). (Choice C) Contact dermatitis is an example of T cell-mediated hypersensitivity (type IV reaction). Skin rash occurs, but systemic manifestations (eg, fever, arthralgias) are not typical. (Choice D) Septic arthritis is due to direct bacterial or fungal invasion of the synovium rather than immune complex deposition. It is most commonly monoarticular rather than polyarticular. Educational objective: A serum sickness-like syndrome in patients in the prodromal phase of acute hepatitis B infection can be attributed to complement activation by circulating immune complexes. Other extrahepatic manifestations of hepatitis B infection explained by circulating immune complexes include polyarteritis nodosa and glomerulonephritis. References: Extrahepatic manifestations of acute hepatitis B virus infection. (http://www.ncbi.nlm.nih.gov/pubmed/23983659) Case records of the Massachusetts General Hospital. Case 10-2013. A 30-year-old man with fever, myalgias, arthritis, and rash. (http://www.ncbi.nlm.nih.gov/pubmed/23514249)

A 33-Year-Old Man with No Prior Medical History Comes to the Emergency