Infantile polyarteritis nodosa presenting as hyponatraemic hypertensive syndrome

The association of arterial hypertension with hyponatraemic dehydration, known as hyponatraemic hypertensive syndrome (HHS), is a rare and serious hypertensive complication. Here, we describe a 17-mo-old girl who presented with severe hyponatraemic dehydration, hypokalaemia, polyuria, and nephrotic-range proteinuria associated with malignant arterial hypertension and systemic inflammatory disease. Diagnosis of classic polyarteritis nodosa (c-PAN) was made on the basis of renal arteriography demonstrating small arterial aneurysms in association with non-aneurismal changes such as arterial cut-off, arterial tapering stenosis and nephrogram perfusion defect. A decrease of blood pressure by antihypertensive treatment resulted in the normalization of HHS abnormalities. However, c-PAN became well controlled only after 4 mo of immunosuppressive therapy. CONCLUSION: The main interest of this case was the uncommon presentation of systemic polyarteritis nodosa in a very young child. Renal ischaemia from intrarenal vessel disease may have been the trigger event for HHS in our case. Management of PAN-associated severe arterial hypertension is based on immunosuppressive and antihypertensive treatment.