• Clinical science

Henoch-Schonlein purpura (Anaphylactoid purpura…)


Henoch-Schonlein purpura (HSP) is an acute immune complex-mediated small vessel vasculitis that most commonly occurs in children. It is often preceded by an upper respiratory tract infection and typically presents with a tetrad of symptoms: palpable purpura, arthritis/arthralgia, abdominal pain, and renal disease. However, in any individual patient, only some of the classic tetrad of symptoms may be present. HSP is a clinical diagnosis, but in particularly unclear or atypical cases a biopsy may be used to confirm the diagnosis. Because the disease course is usually self-limiting, treatment is generally supportive. Severe cases may require glucocorticoids, antihypertensive drugs, and possibly dialysis. HSP has an excellent prognosis, usually resolving within one month when not complicated by significant renal disease.


  • Sex: >
  • Age: more common in children
    • 90% of cases < 10 years [1]
    • Peak incidence: 6 years [2]

Epidemiological data refers to the US, unless otherwise specified.


The exact pathogenesis is unknown and assumed to be multifactorial. Factors that likely play a role include:


Clinical features


  • Symptom onset often 1–3 weeks after an infection, typically affecting the upper respiratory tract [3]

Manifestations [5][1]

HSP is characterized by a tetrad of clinical features: palpable purpura, arthritis/arthralgia, GI symptoms, and renal disease. HSP is one of the important differential diagnoses to consider in cases of pediatric limp.


HSP is a clinical diagnosis; , laboratory tests are not essential to HSP diagnosis. However, they may be useful for excluding differential diagnoses in patients exhibiting only one or two of the HSP tetrad of symptoms, as is often the case in the first few days. Laboratory tests are also useful for monitoring the extent of renal involvement, which helps determine the prognosis. Definitive diagnosis in uncertain cases is made via biopsy. [1][6]

Laboratory tests

The platelet count in HSP is normal or elevated, as opposed to other causes of purpura.


  • Indication: performed in patients with marked abdominal symptoms or suspected complications
  • Modalities: abdominal ultrasound/CT


Differential diagnoses

Clinical feature of HSP Differential diagnosis Distinguishing feature
Purpura [5]
  • No IgA deposition on biopsy
  • Arthritis typically in a single joint
  • No rash, abdominal pain, or renal symptoms
Renal disease
  • No rash, joint, or GI symptoms
  • Primarily affects (young) adults

HSP is a unique cause of purpura without thrombocytopenia.

The differential diagnoses listed here are not exhaustive.


Most cases of HSP are self-limiting and only require supportive care; (e.g., pain management) with regular outpatient follow-up. Severe HSP requires hospitalization and intensive medical therapy.

Mild disease

  • Outpatient treatment
  • Usually no treatment necessary
  • NSAIDs for pain management, rest, and adequate hydration
  • Discontinuation of suspected precipitating drug, if applicable

Severe disease [7]


We list the most important complications. The selection is not exhaustive.