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.