In HHS-affected patients, hair follicles start to shrink or miniaturize, causing the thick hair on the scalp to be replaced by a veneer of thin, baby-fine hair.  The finding is noteworthy because ultimately, the disease may yield clues leading to better options in the treatment of common pattern hair loss, a disorder affecting at least 40 million American men and 20 million American women.

APCDD1, located on Chromosome 18, was found in the genome of several affected families from Pakistan and Italy where HHS goes back generations.  Discussing the importance of the new study, lead author Angela Christiano, Ph.D., professor of dermatology at Columbia University Medical Center, New York, explained "the data is highly significant in terms of fundamental research because the findings suggest that manipulating the Wnt pathway may have an effect on hair follicle growth -- not just in mice, but for the first time, in humans".

Among people with HSS, a flawed version of APCDD1 disrupts a signalling pathway in which genes instruct proteins to turn hair growth on or off.  This so-called Wnt pathway has been extensively explored in lab mice, so observing that it also exists among humans is an important step forward in figuring out the causes of baldness.  The landmark paper appears this week in the British scientific journal Nature.