A previously healthy 11-year-old girl presents to her pediatrician with a rash on her legs and knee pain. She admits to having abdominal pain the day before but her stomach is feeling better today. She denies fever, nausea, vomiting, and diarrhea. The right knee hurts sufficiently that she has been limping since she woke up. Upon exam the child is afebrile and does not appear to be in distress. She has an impressive rash on her legs with right knee swelling (Figure 153-1). The rash is petechial and purpuric and slightly palpable. The linear pattern running down the thigh matches the seams of her pants. A urinalysis performed in the office reveals blood in the urine but no protein. The pediatrician diagnoses Henoch Schonlein purpura (a type of vasculitis) and discusses the treatment plan with the girl and her mother.
FIGURE 153-1
Henoch-Schönlein purpura in an 11-year-old girl. A. In addition to the palpable purpura, this patient also had abdominal pain. Note how the seam of her jeans is visible in the purpuric pattern. B. She also had knee pain and swelling and was walking with a limp. (Used with permission from 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 (HSP) is also known as leukocytoclastic vasculitis. HSP is a type of leukocytoclastic vasculitis.
HSP (Figures 153-1 to 153-3) occurs mainly in children with an incidence of approximately 1 in 5000 children annually.2 It is the most common vasculitis in the pediatric population.3
Although HSP affects all age groups, it is most common in children ages 2 to 6 years old.3–5 The disease affects an estimated 70.3 per 100,000 children per year with a male to female ratio of 1.2:1.3,4
White children have a much higher incidence of HSP compared to black children.3,4
Although the incidence in children has been reported to be about 100 times greater than adults, HSP is typically less severe in the pediatric population.6
FIGURE 153-3
Close-up of palpable purpura from the patient in Figure 153-2. Some lesions look like target lesions but this is Henoch-Schönlein purpura and not erythema multiforme. (Used with permission from Richard P. Usatine, MD.)
HSP is usually benign and self-limiting, and tends to occur in the springtime. It results from immunoglobulin (Ig) A-containing immune complexes in blood vessel walls in the skin, kidney, and GI tract. 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 153-1). 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, the patient should have palpable purpura or petechiae more in lower limbs and one or more of the following:7,8
Bowel angina (pain).
Arthritis or arthralgia.
GI bleeding.
Hematuria (renal involvement).
Leukocytoclastic vasculitis (Figures 153-4 and 153-5) is the most commonly seen form of small vessel vasculitis. Prodromal symptoms include fever, malaise, myalgia, and joint pain. The palpable purpura begins as asymptomatic localized areas of cutaneous hemorrhage that become palpable. Few or many discrete lesions are most commonly seen on the lower extremities but may occur on any dependent area. Small lesions itch and are painful, but nodules, ulcers, and bullae may be very painful. Lesions appear in crops, last for 1 to 4 weeks, and may heal with residual scarring and hyperpigmentation. Patients may experience 1 episode (drug reaction or viral infection) or multiple episodes (RA or SLE). The disease is usually self-limited and confined to the skin. To make the diagnosis, look for presence of 3 or more of the following:9
Age older than 16 years (not for HSP).
Use of a possible offending drug in temporal relation to the symptoms.
Palpable purpura.
Maculopapular rash.
Biopsy of a skin lesion showing neutrophils around an arteriole or venule. Systemic manifestations of leukocytoclastic vasculitis may include kidney disease, heart, nervous system, GI tract, lungs, and joint involvement.
Vasculitis is defined as inflammation of the blood vessel wall. The mechanisms of vascular damage consist of a humoral response, immune complex deposition, or cell-mediated T-lymphocyte response with granuloma formation.10
Vasculitis induced injury to blood vessels may lead to increased vascular permeability, vessel weakening, aneurysm formation, hemorrhage, intimal proliferation, and thrombosis that result in obstruction and local ischemia.10
Small-vessel vasculitis is initiated by hypersensitivity to various antigens (drugs, chemicals, microorganisms, and endogenous antigens), with formation of circulating immune complexes that are deposited in walls of postcapillary venules. The vessel-bound immune complexes activate complement, which attracts polymorphonuclear leukocytes. They damage the walls of small veins by release of lysosomal enzymes. This causes vessel necrosis and local hemorrhage.
Small-vessel vasculitis most commonly affects the skin and rarely causes serious internal organ dysfunction, except when the kidney is involved. Small-vessel vasculitis is associated with leukocytoclastic vasculitis, HSP, essential mixed cryoglobulinemia, connective tissue diseases or malignancies, serum sickness, and serum sickness-like reactions, chronic urticaria, and acute hepatitis B or C infection.
Hypersensitivity (leukocytoclastic) vasculitis causes acute inflammation and necrosis of venules in the dermis. The term leukocytoclastic vasculitis describes the histologic pattern produced when leukocytes fragment.
Some patients with systemic lupus erythematosus (SLE; Figure 153-6) and other connective tissue disorders develop an associated necrotizing vasculitis. It most frequently involves the small muscular arteries, arterioles, and venules. The blood vessels can become blocked leading to tissue necrosis (Figure 153-6). The skin and internal organs may be involved.
FIGURE 153-5
Leukocytoclastic vasculitis in a young man. A. Palpable purpura on the lower leg. B. Involvement of the lower abdomen. (Used with permission from Richard P. Usatine, MD.)
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