By Emma Patten-Hitt

NEW YORK, Mar 20 (Reuters Health) - In some patients with a rare genetic disorder, a simple fever can cause them to lose all of their hair. The hair grows back after the fever has passed, but now researchers think they know the reason why the patients lose their hair in the first place.

Patients with this disorder, called trichothiodystrophy (TTD), already have brittle hair, nails and scaly skin. But some patients with the disorder have an additional burden: during a fever, they can lose their hair in 1 or 2 days.

Dr. Jan H. J. Hoeijmakers from Erasmus University in the Netherlands and colleagues looked at four patients who had TTD and fever-related hair loss. The investigators analyzed the patients' cells and found that high temperatures impaired the cells' ability to repair damaged DNA, as well as to translate genes into proteins--a key process in the body. All four patients had a particular mutation in the gene that causes TTD.

The researchers were particularly interested in this mutation because it is "temperature-sensitive," meaning that it only is activated under conditions of increased heat, such as that produced by fever. Previously, scientists have mostly seen these types of defects in lower organisms such as bacteria and yeast--they have not been fully identified in humans.

Writing in the March issue of Nature Genetics, Hoeijmakers and colleagues speculate that during fever the same defect that causes the hair to be naturally brittle in these patients is aggravated even further and introduces a "highly fragile point at the base of the hair resulting in immediate complete hair loss."

In an interview with Reuters Health, Hoeijmakers said, "The finding explains a previously puzzling observation and makes us aware that these very rare type of mutations exist in the human population."

Patients with TTD also suffer from features of premature aging and the researchers have developed a mouse that has the same genetic defects and symptoms as humans with TTD.

They hope that their research on TTD may shed light on the normal aging process in humans. The authors believe that these patients age prematurely due to a problem with the same malfunctioning protein that causes brittle hair.

"We have recently discovered that a number of the symptoms are associated with accelerated aging, so we hope to obtain insight into the mechanism that underlies aspects of natural aging and age-related disease," Hoeijmakers said.

"It is evident that there will be more disorders--yet to be discovered--in which the defect is temperature sensitive, very much in the same way as has been documented before in lower organisms," Hoeijmakers said.

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