What is a Janus Cat?

A few weeks ago, a unique, two-faced cat named Frankie and Louie earned the Guinness World Record for becoming the longest-surviving Janus cat. Since that time, many have probably been wondering: what exactly is a Janus cat? What causes a feline to have this condition? What is the survival rate of a cat diagnosed with this condition?

With this article, we'll focus on the science behind the Janus cat, and seek to answer the many questions that arise from being exposed to this condition for the first time.

What Exactly is a Janus Cat?

In laymen's terms, a Janus cat is a cat that, like Frankie and Louie, has two faces. They are named Janus cats in reference to the Roman god Janus, who also had two faces.

Scientifically, however, a Janus cat is a feline that suffers from a rare congenital disorder known as craniofacial duplication, or the Greek term diprosopus (meaning "two-faced").

According to MedicineNet.com, diprosopus results in "part or all of the face being duplicated" on some part of the head.

How Does a Cat Become a Janus Cat?

There is no simple explanation, or a concrete one at that, as to why the congenital defects occur. Among other factors, however, scientists point to a protein dubbed the "Sonic Hedgehog homolog (SHH).”

In development, SHH determines how wide facial features are. According to a scientific report on dev.biologists.org, it is believed that excessive amounts of SHH can have "multiple and profound effects on the entire spectrum of craniofacial development."

How Rare Are Janus Cats?

Though it has been documented a few times, Janus cats, like humans that suffer from diprosopus, are extremely rare. 

How Long Can Janus Cats Live?

Like humans that suffer from diprosopus, Janus cats usually don't live very long. Their life expectancy is approximately four days or less.

Frankie and Louie defied those odds, of course, as he has been living for 12 years with the condition.