Rare case of 18-month-old child with Moyamoya disease presenting with tubular dysfunction

A new finding in Moyamoya disease reported the occurrence of hypertension preceded by tubular dysfunction with an atypical hyponatremic-hypertensive syndrome (HHS). unilateral renal artery stenosis accounts for 8%-10% of renovascular hypertension in childhood and rarely causes hyponatremic-hypertensive syndrome (HHS).

Moyamoya disease is a progressive steno-occlusive cerebrovascular arteriopathy of unknown origin involving the distal intracranial internal carotid artery and its main branches and is a rare cause of pediatric stroke. It exhibits a distinguishing feature of the presence of a collateral network of overgrown and dilated small arteries from the circle of Willis that appear as a puff of smoke and hence the name Moyamoya. Different angiographic images are seen in certain disease conditions where such patients are characterized as Moyamoya syndrome.  Majority of the pediatric cases present clinically as ischemic stroke, while some as transient ischemia and hemorrhagic stroke with hemiparesis. Sometimes intracranial bleeding is seen in some adult patients, but children have more epilepsy than adults. Extracranial sites like the carotid, pulmonary, coronary, and renal arteries also show steno-occlusive arterial changes. 

Maria Luisa Conte et al presented a case of an atypical Moyamoya disease in the journal BMC Pediatrics. A18-month-old boy with a recent history of polyuria and polydipsia, having acute febrile gastroenteritis with neurological impairment, severe dehydration, hyponatremia, hypokalemia, kidney tubular dysfunction, and elevated aldosterone and renin even with normal blood pressure. Fluid and electrolyte levels were corrected, and the boy recovered completely.

Radiological findings:

• An abdominal ultrasound showed a smaller right kidney.
• A brain magnetic resonance and an electroencephalogram did not show any relevant abnormalities.
• Five months later when the child experienced left-side hemiparesis after a traumatic concussion and severe hypertension, a brain tomography was done which documented cerebral ischemia. 
• Brain and kidney angiographic studies displayed puff of smoke findings of internal right carotid artery branches and a steno-occlusive pattern of the right renal artery, respectively. 

Thus, the researchers diagnosed it to be Moyamoya disease with HHS secondary to unilateral renal artery stenosis. After an unsuccessful antiplatelet and antihypertensive pharmacological treatment, the boy underwent a renal angioplasty and a cerebral STA-MCA bypass (direct superficial temporal artery-to-middle cerebral artery bypass), significantly improving both neurological and kidney disease. 

This is the first case of the atypical hyponatremic hypertensive syndrome as the onset of Moyamoya arteriopathy in a child, with hypertension following tubular dysfunction and driven by unilateral renal artery stenosis. 

Further reading: Conte, M.L., La Scola, C., Mencarelli, F. et al. Moyamoya disease presenting with tubular dysfunction in a child: pitfalls in diagnosing an atypical hyponatremic-hypertensive syndrome. BMC Pediatr 23, 227 (2023). https://doi.org/10.1186/s12887-023-03926-1