A 21-year-old woman presented with a 3-day history of a painful purpuric rash on her lower extremities (Figure 179-1 and Figure 179-2). The lesions had appeared suddenly, and the patient had experienced no prior similar episodes. The patient had been diagnosed with a case of pharyngitis earlier that week and was given a course of clindamycin. She had not experienced any nausea or vomiting, fever, abdominal cramping, or gross hematuria. Urine dipstick revealed blood in her urine, but no protein. The typical palpable purpura on the legs is consistent with Henoch-Schönlein purpura (HSP).
Henoch-Schönlein purpura presenting as palpable purpura on the lower extremity. The visible sock lines are from lesions that formed where the socks exerted pressure on the legs. (Courtesy of Richard P. Usatine, MD.)
Close-up of palpable purpura from the patient in Figure 179-1. Some lesions look like target lesions but this is Henoch-Schönlein purpura and not erythema multiforme. (Courtesy of Richard P. Usatine, MD.)
Vasculitis refers to a group of disorders characterized by inflammation and damage in blood vessel walls. They may be limited to skin or may be a multisystem disorder. Cutaneous vasculitic diseases are classified according to the size (small versus medium to large vessel) and type of blood vessel involved (venule, arteriole, artery, or vein). Small- and medium-size vessels are found in the dermis and deep reticular dermis, respectively. The clinical presentation varies with the intensity of the inflammation, and the size and type of blood vessel involved.1
Hypersensitivity vasculitis is also known as leukocytoclastic vasculitis.
HSP is a type of leukocytoclastic vasculitis.
- HSP (Figure 179-1, Figure 179-2, and Figure 179-3) occurs mainly in children with an incidence of approximately 1 in 5000 children annually.2 It results from immunoglobulin (Ig) A-containing immune complexes in blood vessel walls in the skin, kidney, and GI tract. HSP is usually benign and self-limiting, and tends to occur in the springtime. A streptococcal or viral upper respiratory infection often precedes the disease by 1 to 3 weeks. Prodromal symptoms include anorexia and fever. Most children with HSP also have joint pain and swelling with the knees and ankles being most commonly involved (Figure 179-3). In half of the cases there are recurrences, typically in the first 3 months. Recurrences are more common in patients with nephritis and are milder than the original episode. To make the diagnosis of HSP, establish the presence of 3 or more of the following:3
- Palpable purpura
- Bowel angina (pain)
- GI bleeding
- Onset ≤20 years
- No new medications
- Some patients with systemic lupus erythematosus (SLE) (Figure 179-4 and Figure 179-5), rheumatoid arthritis (RA), relapsing polychondritis, and ...