Dermatology
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A 6 year old boy is brought to the Emergency Department by his father. He has developed a non-blanching purpuric rash over his lower limbs and is complaining of pain in both knees. He has a history of a recent sore throat. He is otherwise well and has no other past medical history. Which of the following is the most important investigation in this patient?
Answer:
Henoch–Schonlein purpura (HSP) is an IgA-mediated autoimmune systemic condition. The most worrying complication is that of acute kidney injury. Henoch–Schonlein nephritis is indistinguishable from that of IgA nephropathy, characteristically showing a focal and segmental proliferative glomerulonephritis. This may result in permanent and chronic kidney damage. Urinalysis should be done in all patients with suspected HSP to assess the degree of renal involvement. Serum IgA levels may be elevated, but this is not a specific test for HSP. Coagulation studies can be considered to help exclude other causes. Laboratory evaluation including antinuclear antibodies, antineutrophil cytoplasmic antibodies, and complement levels are typically negative and can help differentiate HSP from other vasculitides.Henoch-Schonlein Purpura
Dermatology
Last Updated: 8th September 2021
Henoch-Schonlein purpura (HSP) is the most common vasculitis of childhood, occurring predominantly between the ages of 3 and 15 years, and affecting the small vessels. HSP is characterised by the classic tetrad of rash, abdominal pain, arthritis/arthralgia, and glomerulonephritis.
Causes
The underlying cause of HSP remains unknown. It is an immune-mediated vasculitis, with a variety of infectious and chemical triggers having been proposed as a cause. Many cases of HSP occur after a upper respiratory tract infection (URTI), especially streptococcal infections. Some cases of HSP may be drug related (e.g. penicillin, cefaclor, minocycline, hydralazine, or phenytoin); however, the relationship is unclear.
Diagnosis
HSP is usually diagnosed clinically, based on characteristic features in the history and physical examination; laboratory tests are non-specific. The classic tetrad of rash, polyarthralgias, abdominal pain, and renal disease usually makes the diagnosis straightforward. Skin lesions are characterised as palpable purpura and are typically non-blanching. They can occur anywhere on the body, but are usually concentrated on the lower extremities.
However, while all patients with HSP will present with a characteristic rash, not all patients present with the other classic symptoms. In patients with an unusual presentation, such as pulmonary haemorrhage, headaches, or seizures followed by the development of a rash, a biopsy of an affected organ such as skin or kidney will show IgA deposition, which confirms the diagnosis of HSP.
Other tests:
- Urinalysis should be done in all patients with suspected HSP to assess the degree of renal involvement.
- Serum creatinine and electrolyte levels should be considered in all patients with an abnormal urinalysis.
- Serum IgA levels may be elevated, but this is not a specific test for HSP.
- Coagulation studies can be considered to help exclude other causes.
- Laboratory evaluation including antinuclear antibodies, antineutrophil cytoplasmic antibodies, and complement levels are typically negative and can help differentiate HSP from other vasculitides.
- Imaging by ultrasound is indicated for severe abdominal pain to evaluate for intussusception or perforation. It may also be used to evaluate testicular pain and swelling.
Management
Most cases of HSP resolve spontaneously (usually within 4 weeks) and the primary goal is to provide symptomatic treatment. Complete recovery occurs in 94% of children and 89% of adults. One third of patients may have a recurrence within 4 months, but the subsequent episode is generally milder; recurrences are more common in patients with nephritis.
Symptomatic management:
- Joint pain can typically be managed with either ibuprofen or paracetamol, both of which are considered equally efficacious. Mild to moderate abdominal pain is managed with paracetamol and supportive care.
- Patients with scrotal involvement or severe oedema or severe abdominal pain (based on patient's history, physical examination findings, and clinical judgment) are managed with oral prednisolone. If abdominal pain is accompanied by nausea and vomiting, intravenous corticosteroids may be used. Surgical consultation may be necessary for severe abdominal pain.
Renal involvement:
- Specific treatment is considered only in patients with nephrotic-range proteinuria and/or those with declining renal function, and intravenous corticosteroids (pulse dosing) are recommended.
- Renal impairment with rapidly progressive nephritis generally requires a combination of corticosteroids, immunosuppressants, and plasmapheresis.
- Renal transplant may be required in patients who progress to end-stage renal disease.
Complications
- Pulmonary haemorrhage
- GI haemorrhage and intussusception
- Renal impairment with deterioration of function
- End-stage renal disease
- CNS complications e.g. headaches, seizures
- Ocular complications e.g. keratitis or uveitis
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
