The matted and mussed hair of the famously bizarre German children’s book character Struwwelpeter was meant to serve as a warning about bad hygiene. But for kids that bear a striking resemblance to the straw-haired mischiefmaker (above), tangled hair is no fault of their own: It’s due to a rare genetic mutation. Scientists have now pinpointed the three genes that cause so-called “uncombable hair syndrome,” a hair shaft disorder characterized by dry, frizzy, pale hair that—like the name says—is impossible to comb flat. To indisputably diagnose the condition, hairs are split in half and placed under a high-powered scanning electron microscope. Straight hair appears round, curly hair appears oblique, but uncombable hair is triangular or heart-shaped at the cross section and grooved from root to end. Three genes—PADI3, TGM3, and TCHH—direct the process that causes the misshaped strands, researchers report this month in the American Journal of Human Genetics. If just one of these genes malfunctions, the structure and stability of the hair is affected. Only about 100 cases have ever been reported, though the researchers suspect not all sufferers are reporting their symptoms. Think about it: When was the last time you visited your doctor because of a bad hair day? Fortunately for patients, the snarls seem to become more manageable with age, and the syndrome does not have health implications beyond tangled tresses. As for everyone else, at least you can rest easy knowing your kid’s knots probably aren’t caused by flawed genes.