PARIS - SCIENTISTS say they have pinned down a DNA mechanism that gives rise to a rare but distressing form of baldness that strikes before adulthood.

Flaws in a gene called U2HR are to blame for a condition called Maria Unna hereditary hypotrichosis, or MUHH, named after the German trichologist who identified the problem.

Children with MUHH have sparse or no hair at birth, followed by wiry or coarse hair in childhood but progressively lose it at puberty.

Researchers led by Dr Xue Zhang of the Peking Union Medical College in Beijing found that U2HR, located on Chromosome 8, acts as a key switch in the process.

U2HR controls a small peptide - a kind of mini-protein - that in turn affects a previously-identified protein called the human hairless monolog, or HR, which is crucial for the regeneration of hair follicles.

Sifting through the genome of 19 Chinese families with a history of MUHH, the team found mutations of U2HR led to increased levels of HR, the death of hair follicles and thus greater likelihood of this kind of baldness.

The study, published online on Sunday in the journal Nature Genetics, offers a potential target for drugs that would block this pathway, offering the hope that youngsters who inherit the mutations will one day keep their hair, say the authors. -- AFP