Henoch–Schönlein purpura

Henoch–Schönlein purpura
Typical purpura on lower legs and buttocks
ICD-10
ICD-9
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eMedicine	derm 177 emerg/767 emerg/845 ped/3020
MeSH ID

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Typical purpura on lower leg

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More severe case of HSP on child's foot, leg, and arm

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Immunostaining showing IgA in the glomerulus of a patient with Henoch-Schönlein nephritis

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Microphotograph of a histological section of human skin prepared for direct immunofluorescence using an anti-IgA antibody, the skin is a biopsy of a patient with Henoch-Schönlein purpura. IgA deposits are found in the walls of small superficial capillaries (yellow arrows). The pale wavy green area on top is the epidermis, the bottom fibrous area is the dermis.

Henoch–Schönlein purpura (abbreviated as HSP), also known under several other names including anaphylactoid purpura, purpura rheumatica, and Schönlein–Henoch purpura, is a multifaceted disease predominantly affecting the skin but also has implications for various other organs. Although children are the most commonly affected demographic, it can impact individuals of any age.

Overview

HSP is essentially a systemic vasculitis, which means it results from the inflammation of blood vessels. Its etiological hallmark is the deposition of immune complexes containing the antibody IgA, though the precise trigger for this occurrence remains a subject of research. Its typical clinical manifestations include palpable purpura (small, raised purple spots resulting from hemorrhages), accompanied often by joint pain and abdominal discomfort.

A noteworthy precursor to the onset of HSP is often an infection, with throat infections being a frequent precursor.

Clinical Presentation

The fundamental clinical manifestation of HSP is the appearance of purpura. This is invariably seen in all diagnosed cases. The triad of symptoms that define the disease includes:

Purpura: Palpable and usually visible on the legs and buttocks. However, they can also manifest on the arms, face, and trunk. Arthritis: Joint pains, especially in the ankles, knees, and elbows. Hands and feet may also be affected. The arthritis is non-erosive, so it does not lead to permanent deformity. Abdominal Pain: Often colicky in nature and may be associated with nausea, vomiting, constipation, or diarrhea. In certain cases, blood or mucus may be present in the stools. A subset of patients may also experience gastrointestinal hemorrhage.

Pathophysiology

HSP is primarily a small-vessel vasculitis where immunoglobulin A (IgA) and complement component 3 (C3) complexes are deposited on various blood vessels such as arterioles, capillaries, and venules. This is somewhat similar to the pathology observed in IgA nephropathy, though the latter typically targets young adults and affects mainly the kidneys. HSP, on the other hand, is more prevalent in children and has systemic manifestations including the skin, connective tissues, scrotum, joints, gastrointestinal tract, and kidneys.

Diagnosis

The diagnosis of HSP hinges largely on its unique clinical presentation. Laboratory tests may show:

Elevated levels of creatinine and urea in cases with kidney involvement. Raised IgA levels in approximately 50% of the patients. Increased C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR). A possibly raised platelet count. Histopathologically, skin or renal biopsy can show IgA deposition, aiding in a definitive diagnosis.

Classification

Multiple diagnostic criteria have been proposed for HSP, such as the 1990 American College of Rheumatology (ACR) criteria and the 1994 Chapel Hill Consensus Conference. The 2006 European League Against Rheumatism (EULAR) and Pediatric Rheumatology Society (PReS) classification emphasizes palpable purpura along with at least one additional clinical manifestation for a diagnosis.

Treatment

While HSP often resolves spontaneously, symptom control is essential. Pain management is crucial, especially for abdominal and joint pains. Although steroids are not a mainstay treatment for HSP, early administration in the disease course may mitigate symptoms and potentially reduce the risk of severe renal involvement. However, their role in preventing long-term kidney disease is still debated.

Prognosis

The prognosis for HSP patients is generally favorable. Recovery rates are notably high, especially in children. However, recurrence, especially within the first few months following the initial episode, is seen in a significant proportion of patients. This risk is especially heightened in older children and adults.

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