Henoch-Schönlein Purpura (HSP) is a condition caused by systemic inflammation of the body’s blood vessels. It is most common in childhood and is caused by an autoimmune phenomenon.
The diagnosis of this condition is based upon the characteristic clinical features and diagnostic tests. A purpuric or petechial cutaneous palpable rash presents in the form of reddish non-pruritic non-blanching dots, predominantly over the lower limbs. Diagnosis requires this in addition to at least one of the following:
- Arthritis or arthralgia (which usually resolves in 24-48 hours)
- Diffuse abdominal pain - this is often colicky, associated with vomiting (bowel angina) and is seen in 44% of children. Intestinal colic often disappears within 72 hours without treatment. Serious complications such as intussusception (in 3%), hematemesis or malaena (22%), perforation of the bowel, and pancreatitis, may occur in a few cases.
- Evidence of renal involvement:
- Hematuria positive on dipstick testing - this is found in 9 of every 10 patients, but persists in only 5%. If hematuria is present, the amount of blood in urine should be quantified.
- Proteinuria is defined as total urinary protein > 0.3 g in 24 hours
- Albumin is present in the morning urine albumin or creatinine levels are > 30 µmol/L
- (A few patients may have only signs of renal damage or even renal failure. Some others may have hypertension, or nephrotic range proteinuria.)
- Positive biopsy findings
Other less common symptoms should be enquired for, and include:
- Scrotal pain or edema
- Subcutaneous edema of the hands, sacrum or feet, which may be associated with severe pain
Rare presentations include:
- Cardiac involvement
Biopsy in HSP
The diagnosis is confirmed by biopsy of the skin immunoglobulin deposits, the kidney, or both.
A skin biopsy is taken under local anesthesia. The skin sample is excised and sent for histopathologic examination. The characteristic findings include leukocytoclastic vasculitis and antibody deposits, specifically IgA, in the walls of the small blood vessels in the skin. Both histopathologic examination and immunofluorescent testing are performed.
Renal biopsy is also required at times, and is carried out under local anesthetic, with a fine needle inserted under the guidance of CT scanning or ultrasound. It reveals the characteristic IgA deposits in the glomeruli of the kidneys, along with the presence of proliferative glomerulonephritis. Renal biopsy is important in that it not only allows a definitive diagnosis to be made but helps with determination of treatment, based on the extent of renal involvement. It also helps to determine which patients require follow up.
Formerly a biopsy was not thought essential in the management of this condition. However, the emergence of silent chronic renal failure in patients who had undiagnosed HSP with a paucity of clinical signs has led to the understanding that this condition may be missed. The best way to reliably diagnose it is by a skin or renal biopsy. This will enable proper follow-up and avoidance of renal damage.
Other tests include:
- A full blood count to rule out other types of purpura
- A blood culture to rule out infections such as meningococcemia which may also present with a skin rash