RASH AND ABDOMINAL PAIN IN AN ADOLESCENT -Case 23
A 17-year-old youth is referred urgently to the rheumatology department with a rapidly progressing rash over his buttocks and legs, and severe, cramping abdominal pain. The rash began as flat, red areas which became ‘bumpy’ and then developed into palpable dark red–purple lumps that fail to blanch on pressure. The abdominal pain occurs in spasms and does not appear to relate to food. His bowel habit is unchanged.
This youth is well but clearly very uncomfortable. His pulse rate is 84/min and blood pressure 117/62 mmHg. He has palpable purpura over his buttocks and the backs of his legs. His right ankle is mildly synovitic but otherwise his joints are normal and he has no other stigmata of inflammatory disease. Palpation of his abdomen reveals diffuse tenderness but no guarding or rebound. There is no organomegaly and normal bowel sounds are audible.
A urine dipstick reveals 3+ protein but no blood.
• What are the common causes of purpura?
• What is the most likely diagnosis condition in this case?
• How can this diagnosis be confirmed?
• How would you manage this patient?
Purpura are the result of a spontaneous extravasation of blood from the capillaries into the skin. If small they are known as petechiae, when they are large they are termed ecchymoses. There is an extensive differential diagnosis for purpura:
Causes of purpura
Infection – Meningococcal disease (consider in any patient as it carries a high mortality),Infective endocarditis, Septicaemia
Thrombocytopenia – Idiopathic thrombocytopenic purpura, Thrombotic thrombocytopenic purpura, Marrow failure of any cause
Vascular defect – Senile or steroid-induced purpura, Vasculitis (especially Henoch–Schönlein purpura)
Coagulation defect – Haemophilia
Drugs – Steroids, Sulphonamides
The combination of palpable purpura (distributed particularly over the buttocks and extensor surfaces of legs), abdominal pain, arthritis and renal disease is a classic presentation of Henoch–Schönlein purpura (HSP). HSP is a distinct and frequently self-limiting small-vessel vasculitis that can affect any age; but the majority of cases present in children aged 2–10 years, in whom the prognosis is more benign than the adult form, often remitting entirely within 3–4 months.
The abdominal pain may mimic a surgical abdomen and can presage intussusception, haemorrhage or perforation. The arthritis, in contrast, is relatively mild and tends to affect the knees and ankles. Renal disease is generally mild in children, but its presence and severity determine the prognosis of the condition. Many will experience only a mild glomerulitis with microscopic haematuria, but a crescentic glomerulonephritis may occur, with the development of nephrotic s yndrome or acute renal failure.
The diagnostic test is a skin biopsy which reveals a leucocytoclastic vasculitis with IgA deposition in the affected blood vessels; IgA is also detectable in the renal mesangium. Treatment depends on the severity of the disease. In mild cases, no specific therapy is necessary. The arthritis will in general respond to non-steroidal anti-inflammatory drugs (NSAIDs); steroid therapy is reserved for those with severe abdominal symptoms.
If renal disease is severe (deteriorating renal function, hypertension, nephrotic syndrome or crescents on renal biopsy), high-dose steroids and cytotoxics such as cyclophosphamide may be effective first-line; plasma exchange or intravenous immunoglobulin may be tried in refractory cases.
• Consider HSP in a patient with purpura affecting the back of the legs preferentially.
• Abdominal pain in these patients is a sinister symptom.
• The disease is milder in children and frequently remits spontaneously.