When Mitchel Hammond came home from a camping trip last summer, the first thing his mother said was, "Go wash your face, it's dirty."

The right side of Mitch's forehead was noticeably whiter than the rest of his face, recalls his mother. But a few scrubbings later, Patricia Hammand realized that dirt, or lack of it, wasn't the problem. The right half of her son's face, including his eyebow, had turned white. Patricia Hammond took her son to a pediatrician near their Arlington home, who said Mitchel had vitiligo, a little understood disease that robs the skin of its color. The pediatrician then referred Mitch to a dermatologist.

"He was neither helpful nor very interested," complained Patricia Hammand. "He said he couldn't treat it, but he vaguely mentioned a program at Howard University."

Hammond suspects the dermatologist didn't think the discoloration was a problem, and assumed the family wouldn't be interested in going to a predominantly black institution in the District for help.

Vitiligo is often mistaken for burn scars and is thought by many to be a disease of black people, because the drastic difference in skin color makes it much more noticeable among dark-skinned persons. But vitiligo, which affect 2 to 4 percent of the people in this country, does not discriminate among age, race or sex. Though the disease doesn't seem to affect general health, and is not contagious, it can be a source of motional anguish.

In the case of 11-year-old Mitch and his family, embarrassment was overridden by curiosity. Immediately after talking to the dermatologist, the Hammonds called Howard University, where they were referred to the dermatology department and the vitiligo clinic, headed by Dr. Pearl E. Grimes. Since last October, Mitch has been a twice-a-month patient at the clinic, and because of the treatments he has received, most of the color on his face has returned.

Mitch now considers himself the local "expert" on the disease: he has toured Grimes' laboratories, done as much research as possible and is writing a report on vitiligo for his sixth grade class. If other children tease him, he simply explains what he has, though getting out a word like "vitiligo," pronounced vit-al-EYE-go, takes a bit of tongue twisting.

The Tuesday-Thursday vitiligo clinic at Howard University Hospital is part of a four-year, $2 million National Institutes of Health grant to six facilities including Howard, Yale University, the University of Pennsylvania, Bryn Mawr College, the University of Massachusetts and the Massachusette Eye and Ear Infirmary.

The six centers are investigating the causes of vitiligo, its psychological impact on a person and his or her family, methods of treatment and whether the disease is related to other medical problems.

Few people are aware of the Howard clinic, the only one of its kinds in this area, because few dermatologists know about the disease, and therefore are unwilling to handle vitiligo patients.

Since the clinic opened about 14 months ago, Grimes and her staff have been 180 patients. About one-fourth of the patients are whites.

"Many whites suffer tremendously," says Grimes, referring to the psychological problems of her patients, "especially the darker-skinned Caucasians and those who tan."

Vitiligo can appear on any part of the body, Grimes says, but patients with the ghostly white patches on their hands or face are especially self-conscious.

"For me, the best season is when I can wear a turtleneck and long sleeves," one patient told a reporter. "In the summer I'll have to cover more with makeup."

Treatment for the condition, once mistaken for leprosy, was discovered by ancient Egyptians, who ate psoralen berries, then sunned themselves on the banks of the Nile to coax their natural color back. Psoralen lotion and pills are still used in conjunction with ultraviolet light and are significantly effective for about 40 percent of patients, Grimes said.

"If they are conscientious about taking their medications, they'll get some response," adds Grimes, but "we have no panacea," and it's a time-consuming process.

Enrollment in the clinic costs $35 and subsequent visits, usually scheduled once every week or two, are $10. The costs included prescription medications.

Vitilgo destroys pigment cells, called melanocytes. Though researchers have not discovered how or why the cells are destroyed, they do know that the cells usually do not spontaneously replaces themselves. Psoralen promotes the growth of new pigment cells, and with the help of real or artificial sunlight, the new cells migrate to areas that have lost pigmentation.

Researchers in Connecticut and Massachusetts have found that in some individuals, vitiligo seems to be loosely related to other autoimmune disease -- those where one system of the body works against another, such as diabets, thyroid irregularities and loss of piegment of the eye. In some cases, such as Mitch Hammond's, the disease is hereditary; one of Mitch's cousins and a great-aunt also have vitiligo.

Grimes has found that stress often accompanies the onset of vitiligo. Micth's parents recalled that just before the vitiligo appeared, Mitch received poor grades, which temporarily cost him his job on the school safety patrol.

The Hammands also noticed the telltale blotchy skin on a child on Mitch's soccer team. The patches first appeared on Pablo A. Contillana's stomach when he was four. But when the family moved to the United States from Chile three years ago, the patches rapidly spread to his arms and legs.

"I was kinda nervous about moving here," says Pablo who now speaks English well and claims to be a great soccer player.

The Contillanas had never heard of vitiligo until they met the Hammonds nearly a year ago. Pablo says the discoloration doen't bother him, but Mitch has invited him to Grimes' clinic because it's "neat." Pablo's parents are thinking about it.

Grimes, who also is treating a Chinese patient, says she is interested in treating Pablo to compare the way the disease affects different skin colors.