Rapidly progressive vasculopathy in an infantile-onset fibromuscular dysplasia

Fibromuscular dysplasia (FMD) is a non-atherosclerotic vascular disease that predominantly affects renal and cerebral vessels, causing renovascular hypertension and stroke. Because FMD occurs extremely rarely in early childhood, the clinical presentation at onset and the long-term outcome of childhood-onset FMD remain to be clarified.

A 19-month-old boy presented with moyamoya syndrome, presenting with recurrent ischemic attacks and hemi-convulsive seizures. Systolic blood pressure exceeded 200 mmHg on admission, and abdominal CT angiography revealed bilateral stenosis of the renal arteries with a "string-of-beads" appearance. Intensive care with continuous thiamylal infusion was required to manage recurrent seizures. On Day 34 of admission, a left nephrectomy was performed to control his blood pressure. Pathological analysis revealed medial fibromuscular dysplasia and intimal thickening of the renal artery, confirming FMD. At age 2 years and 3 months, he developed nonconvulsive status epilepticus. After recovery, he showed severe spastic quadriplegia and cognitive decline. Neuroimaging studies revealed rapid cerebral atrophy over an 11-month period of observation.

Exome sequencing for arteriopathy-related genes excluded pathogenic variants or copy number variants spanning FMD-related loci. Cytokine analyses showed an elevated TGF-β1 level in cerebrospinal fluid (125 pg/mL) in comparison with those of controls (n = 5; range 6.8-56.1 pg/mL).

This patient highlights the severe clinical presentation and the rapid deterioration of motor and cognitive functions in an early-onset form of FMD. Childhood-onset FMD might be related to unfavorable outcomes of brain functions due to systemic vasculopathy.