The prognosis of HSP is excellent. Most children have complete resolution of the illness without any significant sequelae. Patients with HSP renal disease (elevated blood urea nitrogen, persistent high-grade proteinuria) are at highest risk for long-term complications, such as hypertension or renal insufficiency, particularly if the initial course was marked by significant nephritis. There is a long-term risk of progression to end-stage renal disease in less than 1% of children with HSP. The rare patients who develop end-stage renal disease may require renal transplantation. HSP may recur in the transplanted kidney.
Kawasaki disease (KD) is a vasculitis of unknown etiology that is characterized by multisystem involvement and inflammation of small to medium-sized arteries with resulting aneurysm formation.
KD is the second most common vasculitis of childhood. It is more common in children of Asian descent. It has been described in variable frequency in all parts of the world; the highest frequency is in Japan. KD most commonly occurs in children younger than 5 years of age, with a peak between 2 to 3 years, and is rare in children older than 7 years. The incidence in the United States is approximately 6 per 100,000 children who are younger than 5 years of age. A seasonal variability has been described with a peak between February and May, but the disease occurs throughout the year.
The clinical course of KD can be divided into three phases, each with its own unique manifestations. Aneurysmal involvement of the coronary arteries is the most important manifestation of KD.
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Lymphadenopathy Fever Without a Source Fever of Unknown Origin
The acute phase of KD, which lasts 1 to 2 weeks, is marked by sudden onset of a high, hectic fever (>40 °C) without an apparent source. The onset of fever is followed by conjunctival erythema; mucosal changes, including dry, cracked lips and a strawberry tongue; cervical lymphadenopathy; and swelling of the hands and feet (Fig. 88-1). Conjunctivitis is bilateral, bulbar, and nonsuppurative. Cervical lymphadenopathy is found in 70% of children and should be greater than 1.5 cm in diameter for the purposes of diagnosis. A rash, which can vary in appearance, occurs in 80% of children with KD and may be particularly accentuated in the inguinal area and on the chest. Extreme irritability is prominent, especially in infants. Abdominal pain and hydrops of the gallbladder, cerebrospinal fluid pleocytosis, sterile pyuria, and arthritis, particularly of medium-sized to large joints, may occur. Carditis in the acute phase may be manifested by tachycardia, shortness of breath, or overt congestive heart failure. Giant coronary artery aneurysms, which are rare but occur most commonly in very young children, can appear during this phase.
The subacute phase, which lasts until about the fourth week, is characterized by gradual resolution of fever (if untreated) and other symptoms. Desquamation of the skin, particularly of the fingers and toes, appears at this point. The platelet count, previously normal or slightly depressed, increases to a significant degree (often >1 million/mm3). This phase heralds the onset of coronary artery aneurysms, which may also appear in the convalescent phase and pose the highest risk of morbidity and mortality. Risk factors for development of coronary artery aneurysms include prolonged fever, prolonged elevation of inflammatory parameters such as the erythrocyte sedimentation rate (ESR), age younger than 1 year or older than 6 years, and male gender.
Figure 88-1 Facial features of Kawa-saki disease with (A) morbilliform rash and nonsuppurative conjunctivitis and (B) red, chapped lips. AB