Classification Tree for the Diagnosis of Henoch-Schonlein Purpura

Henoch-Schonlein Purpura can be diagnosed by using a classification tree approach.

top level	second level	third level	fourth level	diagnosis
palpable purpura present	age at onset <= 20			HSP
	age > 20	extra or perivascular granulocytes on biopsy		HSP
		no granulocytes on biopsy		non-HSP
palpable purpura absent	age <= 20	extra or perivascular granulocytes		HSP
		no granulocytes on biopsy	GI bleeding	HSP
			no GI bleeding	non-HSP
	age > 20			non-HSP

Surrogate criteria:

• if biopsy data not available with palpable purpura and age > 20 years, then GI bleeding may be used

Criteria	Comment
palpable purpura	slightly raised "palpable" hemorrhagic skin lesions, not related to thrombocytopenia
age <= 20 years at onset of first symptom
gastrointestinal bleeding	passage of melena, grossly bloody stool, or a positive result for occult blood in stool (usually by the guiac method)
extravascular or perivascular granulocytes on biopsy	granulocytes in a perivascular cuff around arterioles or venules, or in an extravascular location

Patient Subsets	Findings
HSP patients	palpable purpura present; age <= 20
	palpable purpura present; age > 20; extravascular or perivascular granulocytes on biopsy
	palpable purpura absent; age <= 20; extravascular or perivascular granulocytes on biopsy
	palpable purpura absent; age <= 20; no extravascular or perivascular granulocytes on biopsy; GI bleeding present
non-HSP patients	palpable purpura present; age > 20; no extravascular or perivascular granulocytes on biopsy
	palpable purpura absent; age <= 20; no extravascular or perivascular granulocytes on biopsy; GI bleeding absent
	palpable purpura absent; age > 20

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