Wednesday, September 5, 2007


A 30 year old man comes into your clinic because of this rash shown above. He says that it began around his bellybutton and has spread to his back, his chest, and now his arms. He says, "The rash started a few days ago, but I haven't had any contact with anything new or different. I mean, last week, I got bit by that stupid Arizona coral snake again, but I took some micrurus antivenin. When I was bitten by it last year, I took the same antivenin, so I know I'm not allergic to either the snake or the meds."

On exam, you find no mucosal or pharyngeal lesions. The patient has a temperature of 39 C but he says his temperature has been fluctuating a lot. He also complains about painful knees, wrists, ankles, and shoulders. You notice no swelling in those joints. He says his muscles have been feeling weak. The rest of the exam is normal.

Challenge: What is the diagnosis?

Related Questions:
1. How would you describe that skin lesion?
2. What is the joint complaint called?
3. What type of reaction is this? That is, what is the pathogenesis?

Image is in the public domain.

1 comment:

Craig said...


This is serum sickness with the cardinal features of rash, fever, and polyarthralgias. The skin lesion is best described as urticaria (hives) with raised, red skin welts. The rash can also present as a morbilliform rash, frequently pruritic. The joint complaint is arthralgia (rather than arthritis). The serum sickness occurred because the patient had developed antibodies against the antiserum derived from an animal source. The antivenin he took was probably made from an equine, rabbit, or ovine source. The first time he received antivenin, he sensitized his immune system to the antisera. The later reaction is Type III immune complex hypersensitivity. Antigen-antibody complexes deposit into the tissue, causing inflammation.

Sources: Wikipedia, UpToDate.