Serum sickness

Background

• A type III hypersensitivity reaction
  • Secondary to injection of anitoxins (e.g. tetanus, rabies)
• Reactions secondary to the administration of nonprotein drugs
  • Amoxicillin, cefaclor, cephalexin (Keflex), trimethoprim-sulfamethoxazole

Diagnosis

1. Primary occurs 6-21 days after exposure
   1. 1-4 days after subsequent exposures to the same antigen
2. Fever
3. Arthralgia
4. Lymphadenopathy
5. Skin eruption (rash)
   1. Urticaria
   2. Scarlatiniform rash
   3. Maculopapular or purpuric lesions
   4. Erythema multiforme

DDX

1. Erythema Multiforme
2. Mononucleosis
3. Polymyositis
4. Systemic Lupus Erythematosus
5. Tick-Borne Diseases, Rocky Mountain Spotted Fever
6. Toxic Epidermal Necrolysis

Treatment

1. D/C antigen
2. Diphenhydramamine
3. Prednisone

Disposition

Admit for:

1. Significant comorbidities (advanced or very young age, immunocompromised)
2. Severe symptoms
3. Hemodynamic instability/hypotension
4. Unclear diagnosis

Prognosis

1. Symptoms usually last 1-2 weeks before spontaneously subsiding
2. Long-lasting sequelae generally do not occur
3. Fatalities are rare and usually are due to continued administration of the antigen