FMD in children and adolescents
FMD may also be diagnosed, although more rarely, in children and adolescents.
In contrary to FMD in adults, FMD in children is generally of the focal type, and may be associated with a stenosis of the abdominal aorta (“coarctation of the abdominal aorta” or “mid-aortic syndrome”).
All medium sized arteries have the potential to be affected by FMD, however, the renal arteries are the most frequently involved.
How frequent multivessel FMD (i.e. FMD affecting more than a single arterial bed) is in children is not well known, and screening for FMD in other arterial locations should be discussed on a case by case basis.
When should FMD be considered?
FMD lesions in children most frequently affect the renal arteries, therefore it is most often diagnosed on the occasion of a work-up for hypertension.
Renal FMD is typically found in a child aged 6-10 years, presenting with grade 2 hypertension. The child is usually in good health, although he/she may complain of experiencing regular headaches.
In younger children, who rarely have blood pressure measured, the diagnosis may be made either, if there are complications due to the hypertension (signs of heart failure, dyspnea or failure to thrive) or during examination for another pathology.
FMD is also considered a possible cause of stroke (CVA, Cerebrovascular Accident) in young children, sometimes in the first year of life, but the diagnosis is difficult to establish.
Is it frequent?
The prevalence of FMD in children can only be estimated, in relation to the prevalence of renovascular hypertension. The prevalence of symptomatic renal artery stenosis in children may be in the range of 1/1000 to 4/1000, the largest part being due to focal FMD. Estimates vary on the ratio girl-boy between 3-2 and 1-1. The female predominance is therefore seen less in children than adults.
How is it diagnosed?
Diagnosis relies on medical imaging (duplex ultrasound, MRA-Magnetic Resonance Angiography, CTA -Computed Tomography Angiography or angiography by catheter) to visualize the lesions and define treatment options.
Note the interest of using duplex ultrasound in children: the different organs are well visible and the examination is neither painful, nor requires radiation, so it may be repeated.
However, in case of strong suspicion of renal artery FMD in a child with severe or complicated hypertension, it is justified to proceed to angiography by catheter to confirm diagnosis and if found, to treat the lesions.
Evidence of a focal renal artery stenosis is not sufficient to establish the diagnosis of renal artery FMD, as a series of rare conditions ( Neurofibromatosis type 1, Williams syndrome, Alagille syndrome …….) need to be excluded.
The diagnosis of FMD in children is therefore a diagnosis of exclusion which should be made in a specialized centre.
What treatment will be offered?
The treatment of FMD related hypertension would be medical (by antihypertensive medication) and/or interventional (angioplasty, classic open surgery) depending on the symptoms and the type of lesions.