the case of the sixteen-year-old infant

Brooke Greenberg is sixteen years old. In a way. Due to a yet-unknown series of genetic (and maybe epigenetic) factors, she is an infant; her development is, in a word, "disorganized." Andy Coghlan of NewScientist explains:

When Walker and his colleagues sequenced Brooke's DNA, they found that the genes associated with the premature-ageing diseases were normal, unlike the mutated versions in patients with Werner's Syndrome and progeria. "That was the first thing we looked at," he said.

Nor does the analysis support the idea that Brooke is somehow "frozen-in-time", in perpetual infanthood. Instead, Walker and colleagues found that different parts of her body and anatomy are maturing at different rates.

"I think she has differential growth of her body," says Walker. "It's not growing like a unified organism, but in fragmented parts."

Her brain, for example, is scarcely more mature than that of a newborn infant. Although she can recognise her mother and make gestures and noises to articulate her wishes, she can't talk.

Yet her bones – although still abnormally short – are around 10 years old, as determined by the maturity of the cells and structures. And despite being a teenager, she still has her baby teeth, with an estimated developmental age of about eight years....

Walker thinks that Brooke is the first recorded case of what he describes as "developmental disorganization". His hypothesis is that the cause is disruption of an as-yet unidentified gene, or genes, that hold the key to ageing by orchestrating how an organism matures to adulthood, reproduces, then gradually ages and dies.

An incredible, existentially baffling case.