- Henoch-Schönlein Purpura (Anaphylctoid purpura)

Henoch-Schönlein Purpura (Anaphylctoid purpura)

Immune complex mediated disease contain IgA within capillaries of skin, GI and renal involvement.
Incidence:

• HSP is the commonest generalized vasculitis of childhood.
• HSP is the commonest cause of non-thrombocytopenic purpura in children.
• Can occur at any age but peaking at 3–10 years of age.
• Male : female = 2:1
• Peaks during the winter months.

Etiology: the cause is unknown.
- It is postulated that genetic predisposition and antigen exposure increase circulating IgA levels and disrupt IgG synthesis.
-The IgA and IgG interact to produce complexes that activate complement and are deposited in affected organs, precipitating an inflammatory response with vasculitis.
- Antigen may be:

• Infections (e.g. Group A ß hemolytic streptococci or ohers)
•  Insect bites
• Drugs or food allergy.

Pathology and pathogenesis:

• IgA-mediated vasculitis of small blood vessels with IgA deposits seen in these vessels, primarily those of the skin and intestine.
• Deposition of polymeric immunoglobulin A (IgA) in glomeruli. 
• IgA deposits are present by immunofluorescence,
•  Broad spectrum of glomerular lesions that can range from mild proliferation to necrotic and crescentic changes can be seen

Clinical presentation:
Preceded 1-3 weeks by upper respiratory tract infection.
It can affect one or more of 4 systems:
A. Skin: 95-100%

• Lesion: maculopapular urticarial rash (palpable and itchy), and may recur over several weeks.
•  Color: red→ purple → rusty brown → then fades.
• Site: symmetrically distributed over the buttocks, the extensor surfaces of the arms and legs, and the ankles. The trunk is usually spared.
• The rash is the first clinical feature and is the cornerstone of the diagnosis, which is clinical.
•  Ecchymosis and purpuric eruption
• They may have oedema, especially of hands, feet,face and/or scrotum.
• Spontaneous resolution occurs in up to 94% within 4 weeks.

  

  Typical purpura on lower legs and buttocks, by Madhero88 - http://www.dermnet.com/Henoch-Schonlein-Purpura/picture/14796

   

B.  Joints:75%

• Migratory polyarthritis or arthralgia "similar to that of rheumatic fever" with Periarticular oedema.
• But the joint not tender as that of rheumatic fever as reaction occur in small blood vessels while in the RF occur in the pain sensitive synovia.
• Not occur in small joints.
• Long-term damage to the joints does not occur, and symptoms usually resolve before the rash goes.

C.  GIT:50%

• Severe Abdominal pain
• Hematemesis, melena.
• Bloody diarrhea.
• Ileus, protein-losing enteropathy.

D.  Renal: 25-50% (worst prognosis)

• The nephritis associated with HSP usually follows onset of the rash, often presenting weeks or even months after the initial presentation of the disease.
• The severity of the systemic manifestations does not correlate with the severity of the nephritis.
• Features include:

-    Gross hematuria,
-    Microscopic hematuria,
-    proteinuria,
-    nephrotic/nephritic picture,
-    renal impairment
-    hypertension

complications:

•  The extra renal symptoms typically resolve rapidly without complication, and the long-term prognosis is mainly dependent on the severity of renal involvement.
• Complications involve:

-    Intussusception (due to hematoma in intestinal wall) can occur and can be particularly difficult to diagnose under these circumstances.
-    Orchitis and testicular torsion,
-    Subarachnoid or cerebral hge.
-    Chronic renal failure

Risk factors for progressive chronic kidney disease are in which Renal biopsy is indicated:
-    heavy proteinuria
-    oedema
-    hypertension
-    deteriorating renal function,

Investigations:

• All investigations of bleeding tendency are normal except Hiss test which may be +ve.
• Investigation for streptococcal infection: ASO titer.
• Urine analysis: to detect renal affection: should be performed weekly in patients with HSP during the period of active clinical disease. Thereafter, a urinalysis should be performed every 1mo for up to 6 mo. If all urinalyses are normal during this follow-up interval, nephritis is unlikely to develop.
• Occult blood in stool
• Serum IgA may be elevated
• Skin biopsy: definitive diagnosis for skin vasculitis which show:

- IgA deposits
- Necrotizing vasculitis with perivascular cuffing with PMN.

• If renal involvement is severe, consider complement C3, C4, antinuclear antibody (ANA), ANCA, ASOT and anti-DNase B, renal ultrasound and percutaneous renal biopsy.
• Renal function tests.

Treatment:

• Penicillin: if it 2ry to streptococcal infection.
• Arthritis: Acetyl salicylic acid (as for rheumatic arthritis)
•  GIT affection: prednisone (1-2 mg/kg/day oral) (absolute indication)
• Renal affection:

- immune suppressive drugs
e.g cyclophosphamide (endoxan) & azathioprine (Imuran)
- dipyridamole
- High-dose IV immunoglobulin G (IVIg)

• Corticosteroids alleviate the extrarenal symptoms of HSP effectively but do not prevent the development of nephritis.

Follow up:
Follow-up for renal dysfunction, hypertension and proteinuria for at least 1 year, or longer if these problems persist.

PROGNOSIS

• The prognosis is very good as it is usually self-limited with complete resolution by a mean of 1 month.
• Recurrence can occur at least for 6 Months. 
• Microscopic haematuria may persist, or macroscopic episodes occur after subsequent upper respiratoray tract infections.
• 1-5%  have long-term renal problems, with hypertension, proteinuria or renal dysfunction.
•  It uncommonly recurs in renal transplants.

Ibrahim Samaha