Williams syndrome — branching viva

Opening framework

My framework has four layers. First, the pattern — a dysmorphic infant with a murmur, hypertension, and metabolic disturbance points to a contiguous-gene microdeletion syndrome. Second, the gene — the cardiovascular phenotype is driven by ELN haploinsufficiency, producing an elastin arteriopathy. Third, the test — a chromosomal microarray confirms the 7q11.23 deletion. Fourth, the family — the deletion is autosomal dominant, so a parent who carries it confers a 50 percent recurrence risk. [1] [2]

The diagnosis and the gene

The unifying diagnosis is Williams, or Williams-Beuren, syndrome, caused by a microdeletion at chromosome 7q11.23 of approximately 1.5 to 1.8 megabases, removing 26 to 28 genes. The gene that drives the cardiovascular and connective-tissue phenotype is ELN, the elastin gene: loss of one copy removes arterial elastic lamellae. I confirm the deletion with a chromosomal microarray, which is first-line because it detects the submicroscopic deletion and defines its size; a conventional karyotype will miss it. FISH with a 7q11.23 probe is the historical confirmatory test and remains useful for family cascade testing. [2] [5]

Why stenosis, not aneurysm

The mechanism of the arteriopathy is the key teaching point. With only one ELN copy, the arterial media lays down fewer, thinner elastic lamellae, and the vessel wall compensates with excessive smooth-muscle proliferation and a thickened, disordered media. The result is a diffuse, stenotic arteriopathy — the narrowing appears at the supravalvular aorta, the peripheral pulmonary arteries, the renal arteries, and the coronary arteries. This contrasts with the aneurysmal dilation seen in disorders of fibrillin matrix integrity such as Marfan syndrome, where the weakened wall dilates. The clinical consequences are supravalvular aortic stenosis, peripheral pulmonary stenosis, systemic and renovascular hypertension, and — most dangerously — coronary artery stenosis causing sudden death under anaesthesia and with exertion. [3] [5]

The cardiac surveillance obligation

Because the arteriopathy is progressive, the heart is never "cleared" — it is reassessed. The surveillance is cardiology-led and lifelong: a baseline echocardiogram at diagnosis defining the supravalvular aortic stenosis gradient, peripheral pulmonary stenosis, coronary origins, and ventricular hypertrophy; serial echocardiography tracking progression; four-limb blood pressure at every visit; and advanced CT or MR coronary angiography when symptoms, high-risk anatomy, or planned anaesthesia demand it. Surgical or catheter intervention is considered for progressive or high-gradient supravalvular aortic stenosis and for significant coronary lesions. Critically, no anaesthetic or sedation proceeds without dedicated cardiac and coronary assessment, because sudden cardiac death under anaesthesia is the feared complication. [3] [7]

Branch: the hypercalcaemia

The finding of hypercalcaemia is part of the syndrome — the historical name idiopathic infantile hypercalcaemia captures it. It reflects abnormal vitamin D and calcium metabolism and is usually transient but can be severe. I manage it with dietary restriction of calcium and vitamin D, avoidance of unnecessary supplementation, a low-calcium formula where levels are elevated, and periodic serum calcium monitoring in the first years. In the rare hypercalcaemic crisis with dehydration, vomiting, and polyuria, I admit for intravenous hydration and, under specialist metabolic guidance, consider bisphosphonates. The aim is to prevent nephrocalcinosis, irritability, and failure to thrive without inducing osteopenia from over-restriction. [6] [1]

Closing: inheritance and the family

The closing point is the inheritance and the counselling. Most cases are sporadic — a de novo deletion arising through low-copy-repeat-mediated unequal crossing-over at 7q11.23 — but the deletion behaves as autosomal dominant: an affected parent has a 50 percent recurrence risk per pregnancy. So once a child is diagnosed, I assess both parents clinically, offer testing where there is any suspicion, and arrange formal genetic counselling including prenatal and preimplantation options. I also confirm that I am not dealing with isolated familial supravalvular aortic stenosis — an ELN point mutation with normal facies and cognition — which carries the arteriopathy but a different developmental prognosis and counselling. The trap is to treat the diagnosis as purely cardiac and forget the cognitive profile, the calcium, and the family: the fluent, sociable speech masks real intellectual disability, and the deletion may run in the family. [1] [5]