Henoch-Schonlein Purpura (Anaphylactoid Purpura)

Pathophysiology

1) type of small vessel vasculitis thought to be secondary to immune complex deposition 2) most commonly occurs in children, but can occur in adults 3) typically self-limited

Signs and Symptoms

1) palpable purpura – most common over legs and buttocks 2) polyarthralgias – typically knees and ankles 3) GI complaints – colicky abdominal pain, nausea, vomiting, bloody diarrhea, and constipation 4) blood and mucus per rectum 5) glomerulonephritis – usually resolves spontaneously 6) myocardial dysfunction – adults only

Characteristic Test Findings

Laboratory – 1) proteinuria 2) microscopic hematuria 3) RBC casts in urine 4) increased serum IgA 5) eosinophilia 6) mild leukocytosis 7) all coagulation tests are normal

Histology/Gross Pathology

1) IgA deposits in walls of dermal blood vessels 2) increased vascular permeability 3) glomerular lesions identical to IgA nephropathy (Berger’s disease)

Associated Conditions

increased incidence with – 1) upper respiratory tract infection 2) immunizations 3) insect bites 4) streptococcus pharyngitis

Biochemistry

IgA is predominant antibody class in deposited immune complexes

Inheritance/Epidemiology

1) peak incidence in spring 2) slightly more common in males

Treatment

1) glucocorticoids (prednisone) decrease GI complaints and joint pain but do not alter overall course 2) if renal failure is rapidly progressive (which is uncommon), plasmapheresis and immunosuppressive drugs are used

Tips for USMLE

if questions mentions a 6 year-old boy with a bad cold who 2 weeks later develops red, raised lesions on his buttocks and the back of his thighs, sore ankles, and abdominal pain, think Henoch-Schonlein purpura