Pediatric emergency medicine trisk 2957 2957
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involving smaller vessels often can be visualized only by use of conventional
angiography.
The reference standard for diagnosing vasculitis remains histopathologic
demonstration of vascular inflammation, although tissue specimens may not be
available in many cases because of the inaccessibility of lesions or patchiness of the
vascular involvement.
Management
See sections below for PAN and KD.
POLYARTERITIS NODOSA
Current Evidence
The annual incidence of PAN in adults is approximately 0.3 per 100,000; no
comparable data are available for children. Corticosteroid therapy has reduced
mortality from nearly 100% to approximately 20%.
PAN is characterized by focal, pan-mural, necrotizing inflammation of small- and
medium-sized muscular arteries. As the name implies, vessels affected by PAN
typically develop nodules in the walls of muscular arteries. Sites of bifurcation are
particularly prone to involvement, presumably because of hemodynamic turbulence at
these points. Biopsies reveal a cellular infiltrate initially predominated by
polymorphonuclear leukocytes and fibrinoid necrosis. As lesions mature, mononuclear
cells, thrombosis, and recanalization mark the healing process.
The etiology of PAN is unknown, although it is considered to be an archetype of
immune complex–mediated vascular damage. Most children with PAN have serologic
evidence of an antecedent streptococcal infection; up to one-third of adults have
chronic hepatitis B or C, with viral proteins demonstrable in the circulating and fixed
immune complexes. The incidence of hepatitis-associated PAN in children is
significantly lower, particularly in Western countries.
Clinical Considerations
Clinical Recognition
Childhood PAN occurs in both cutaneous and generalized forms, and distinguishing
between them may be difficult. Both types display systemic manifestations, including
fever, malaise, and myalgias. However, generalized PAN is significantly more likely to
also involve the renal, GI, and central nervous systems. Common to both are rashes,
although these are more likely to be nodular or lacy (so called livedo reticularis) in the
cutaneous form, and urticarial, petechial, or ischemic in the systemic form. Renal
involvement (including proteinuria, abnormal urinary sediment, and hypertension),
abdominal pain (often a manifestation of gut vasculitis), arthritis, mononeuritis
multiplex, and CNS involvement (seizures, hemiparesis) typify generalized PAN. Less
