At some point or another, every weary parent wonders if their toddler’s hair is an impossible tuft of snags and snarls. But for a few rug rats, tangled hair is a real problem.

A rare genetic condition, called Uncombable Hair Syndrome, marks kids with hairdos best described as electrocution-inspired. These frizzy, wiry locks, often with a silvery blond or straw color, grow into untamable manes of fuzz. Scientists first documented the coiffure condition in 1973, but it is thought to have inspired the famous 1845 German children’s book character “Shockheaded Peter” (Struwwelpeter), later translated by Mark Twain to “Slovenly Peter.”

Since the '70s, scientists have documented around 100 cases, but it’s likely that many more have gone undiagnosed. The condition rears its unkempt head between the ages of three months and 12 years, usually improving as a child grows. Scientists knew little else about it other than that the condition appeared to have a genetic root, sometimes getting tangled in family lines.

Now, after combing through the genetics of 11 children affected by the syndrome, a team of scientists has teased out mutations in three genes that seem to be the cause. One of the genes contains the blueprints for a key protein in hair shafts. The other two genes code for enzymes that essentially act like masonry workers, preparing the protein for hair shaft assembly, then locking it into place among thin strands of keratin (a fibrous component of hair, nails, and skin). The findings were published Thursday in The American Journal of Human Genetics.

Using cell culture experiments, the team, led by hair expert Regina Betz at the University of Bonn, found that mutations in any one of the three genes frazzled the normal development of hair, producing misshapen shafts. This echoes what’s seen in affected kids. Normally, a cross-section of a strand of hair is circular. But the hair of kids with UHS often have triangular or heart-shaped cross-sections.

The team next engineered mice to have the same mutations, resulting in rodents with wavy fur and crinkled whiskers.

"From the mutations found, a huge amount can be learned about the mechanisms involved in forming healthy hair, and why disorders sometimes occur," Betz said in a press statement. "At the same time, we can now secure the clinical diagnosis of 'uncombable hair' with molecular genetic methods."

The American Journal of Human Genetics, 2016. DOI:10.1016/j.ajhg.2016.10.004 (About DOIs).