A 16 y.o. female came to the ED with pain in the L shoulder and a diffuse rash.

BP was 99/55, lactate was 2.2. She was judged to be fluid depleted by IVC US and 4 L was given. She had delayed capillary refill. Antibiotics were started in case this represented toxic shock. Epinephrine was given in case this represented anaphylaxis. The CRP was 56, sed rate was normal. US of the shoulder was normal and no abscess was seen.

this was an image of the patients back with an area of edema

A lesion developed on her back. what do you think caused this?

Our patient was thought initially to have toxic shock or an allergic reaction but within 24 hrs she developed the classic lesion of a brown recluse spider bite with systemic symptoms of  loxoscelism.  She began to hemolyze and her hemoglobin dropped to 7.2 requiring transfusion.  

note the violin shape on the body of the spider. The spiders can be this large but are often smaller.

Loxoscelism refers to both a local and systemic reaction to the bite of the brown recluse spider.  It was first described in Tennessee in 1879. Rash, fever, nausea and vomiting have all been reported .  More serious reactions like hemolytic anemia may require transfusion as in our patient.  DIC may occur with resultant thrombocytopenia  as  well as  myonecrosis and rhabdomyolysis . 

The local reaction is caused by sphingomyelinase D which dissolves cell membranes which results in a necrotic lesion at the site of the bite. The spider biting apparatus is short and bites are only possible  in experimental animals with pressure on the spiders back suggesting many bites occur when a spider is trapped in a shirt sleeve or pants leg.

Brown recluse spiders are found routinely in Missouri

Antivenom is available but must be given within 12 hours and most bites to not come to attention in that time frame. The brown recluse demonstrates the only proven type of necrotic arachnidism in humans.  A second similar case was also seen.  A 21 y.o presented four days after a bite with myalgias, pruritis and dark urine.  He had hemolytic anemia as well with a Hgb that dropped from 16 to 10. Both patients recovered without sequellae.

The second poisonous spider to worry about in the US is the Black widow spider.  They   are common in North America and their bite can produce muscle pain, cramping and mild paralysis of the diaphragm. These spiders have a red hour-glass shape on their ventral surface.

The black widow has an hour glass shape on the ventral surface and eats her mate; hence the name.

TRIVIA

As if it wasn’t enough to worry about brown recluse and black widow spiders, A family in England was forced to move out of their house because it became infested with Brazilian wandering spiders which are poisonous and cause salivation,  arrhythmias and prolonged priapism in men.  An egg sac  had been deposited on a bunch of bananas shipped to the the family’s grocery store.  The egg sac broke open and “banana spiders” infested their home.

Other venomous spiders include Yellow sac spiders found in Mexico and the US and wolf spiders which can cause nausea, dizziness and tachycardia.

the wolf spider

Appel, M, Bertoni da Silveira R, Gremski W et al.  Insights into  brown spider and loxoscelism  Invertebrate Survival Journal.  University of Modena and Reggio Emilia 2(2):152-158.

Fisher R, Kelly  P,  Krober M, et al.  Necrotic arachnidism. 1994.  Western Journal of Medicine. 160(6):570-2.

Barbaro K, Knysak I, Martins R, et al. Enzymatic characterization, antigenic cross-reactivity and neutralization of demonecrotic activity of five loxosceles spider venoms of medial importance in the Americas. 2005 Toxicon 45(4):489-99.

Dr. Schwarz, toxicology weighing in:

Just to clarify on the antivenom, there are recluse antivenoms for generally more toxic species; there really isn't an antivenom available in the US. It is also unclear how efficacious some of the antivenoms are even in some of the other countries.

There is a fab 2 product (not US approved) for black widow spiders. If needed you might be able to get it imported but really aggressive sedation is the key. We used to give calcium but that no longer is really recommended, outside of maybe board exams.