IgA Vasculitis Nephritis

IgA vasculitis nephritis is glomerular inflammation with mesangial IgA deposition in IgA vasculitis, a small-vessel vasculitis of the skin, joints, gut and kidney.

• It is the commonest childhood vasculitis (peak 3 to 10 years); kidney involvement occurs in 30 to 50 percent, usually within 4 to 6 weeks of onset and in over 90 percent within 3 months.
• Triggers: upper respiratory infection (often streptococcal), other infections, drugs, vaccines.
• Adults are less often affected but have more severe renal disease and a worse long term outcome.

Palpable purpura on the buttocks and lower limbs, arthralgia or arthritis (knees, ankles), colicky abdominal pain with vomiting and melaena, scrotal swelling.

• Renal: microscopic or macroscopic haematuria, proteinuria, hypertension, oedema, nephritic or nephrotic syndrome, acute kidney injury.
• Differential diagnosis: IgA nephropathy, post-infectious glomerulonephritis, ANCA vasculitis, lupus nephritis, immune thrombocytopenic purpura, meningococcaemia, haemolytic uraemic syndrome, acute abdomen, acute scrotum.
• Complications: intussusception, bowel infarction and perforation, gastrointestinal haemorrhage, rapidly progressive glomerulonephritis, hypertension, chronic kidney disease (1 to 2 percent of children, 20 percent or more of adults with nephritis), end stage kidney disease, pulmonary haemorrhage, neurological involvement, relapses (one third).

Clinical, based on purpura with arthritis, abdominal pain or nephritis; normal platelets and clotting.

• Urinalysis (dysmorphic red cells, red cell casts), urine protein-to-creatinine ratio, creatinine, urea, electrolytes, albumin, full blood count, C-reactive protein, serum IgA (raised in half), C3 and C4 (normal), antistreptolysin O.
• Skin biopsy shows leucocytoclastic vasculitis with IgA on immunofluorescence.
• Abdominal ultrasound for intussusception and bowel wall thickening.
• Kidney biopsy for heavy proteinuria (above 250 mg/mmol), persistent proteinuria beyond 4 weeks (above 100 mg/mmol), nephrotic or nephritic syndrome, reduced eGFR, or atypical features; crescents above 50 percent of glomeruli indicate severe disease.

Supportive: rest, hydration, analgesia with paracetamol (15 mg/kg every 6 hours in children, 1 g in adults); avoid NSAIDs when nephritis is present; blood pressure and urine monitoring.

Pharmacological

• Mild disease (isolated haematuria, normal blood pressure, minimal proteinuria): observation only.
• Persistent proteinuria or hypertension: ACE inhibitor (enalapril 0.1 to 0.5 mg/kg/day in 1 to 2 doses in children, or ramipril 2.5 to 10 mg daily in adults) or an angiotensin receptor blocker (losartan 0.7 to 1.4 mg/kg/day, adults 50 to 100 mg daily); monitor potassium and creatinine.
• Moderate nephritis (proteinuria with preserved function): prednisolone 1 mg/kg daily (maximum 60 mg) for 4 weeks then taper over 4 to 8 weeks.
• Severe nephritis (crescents above 50 percent, rapid decline): methylprednisolone 10 to 30 mg/kg IV (maximum 1 g) daily for 3 days, then prednisolone 1 mg/kg daily with cyclophosphamide (500 mg/m2 IV monthly for 6 months) or mycophenolate mofetil (600 mg/m2 twice daily in children, 1 g twice daily in adults).
• Severe gastrointestinal disease: prednisolone 1 to 2 mg/kg daily; intussusception needs reduction or surgery.
• Arthritis: paracetamol; prednisolone short course if needed.

Procedures: plasma exchange (7 to 14 sessions) for crescentic disease with rapidly failing function in selected cases; dialysis for kidney failure; kidney transplantation (recurrence in 30 to 50 percent, graft loss in 10 to 15 percent).

Special groups: children (usually self-limited), adults (older age predicts worse outcome; screen for malignancy and drugs), pregnancy (prior nephritis raises hypertension and pre-eclampsia risk).

Red flags: nephrotic syndrome, creatinine rise, severe abdominal pain, melaena, hypertension, crescents on biopsy.

Follow-up: blood pressure and urinalysis weekly for 1 month, monthly for 6 months, then every 3 months; at least 5 years of monitoring after the acute episode (nephritis can appear late); counsel women about pregnancy.