A SERIOUS disorder of the immune system that has been known to doctors for less than a year - a disorder that appears to affect primarily male homosexuals - has now afflicted at least 335 people, of whom it has killed 136, officials of the Centers for Disease Control in Atlanta said yesterday. Federal health officials are concerned that tens of thousands more homosexual men may be silently affected and therefore vulnerable to potentially grave ailments.
Moreover, this immune-system breakdown, which has been implicated in a rare type of cancer, called Kaposi's sarcoma, and seems to invite in its wake a wide variety of serious infections and other disorders, has developed among some heterosexual women and bisexual and heterosexual men.
At a recent Congressional hearing, Dr. Bruce A. Chabner of the National Cancer Institute said that the growing problem was now ''of concern to all Americans.''
The cause of the disorder is unknown. Researchers call it A.I.D., for acquired immunodeficiency disease, or GRID, for gay-related immunodeficiency. It has been reported in 20 states and seven countries. But the overwhelming majority of cases have been in New York City (158), elsewhere in New York State (10), New Jersey (14) and California (71)
Thirteen of those affected have been heterosexual women. Some male victims are believed to have been heterosexual, and to have been chiefly users of heroin and other drugs by injection into their veins. But most cases have occurred among homosexual men, in particular those who have had numerous sexual partners, often anonymous partners whose identity remains unknown.
According to both the Centers for Disease Control and the National Cancer Institute in Bethesda, Md., GRID has reached epidemic proportions and the current totals probably represent ''just the tip of the iceberg.'' Preliminary results of immunological tests have led some Federal health officials to fear that tens of thousands of homosexual men may have the acquired immune dysfunction and be at risk for developing complications such as Kaposi's cancer, infections and other disorders at some future date.
GRID is ''a matter of urgent public health and scientific importance,'' Dr. James W. Curran, a Federal epidemiologist who coordinates the Centers for Disease Control's task force on Kaposi's sarcoma and opportunistic infections, told the Congressional hearing. Opportunistic infections are those that rarely cause illness except in those whose immunological resistance has been lowered by drugs or disease.
More than human suffering is involved. Hospital costs have reached more than $64,000 per patient, and Dr. Curran said that if such costs are typical, ''the first 300 cases account for an estimated $18 million in hospital expenses alone.''
Experts currently think of GRID as a sort of immunological time bomb. Once it develops, it may stay silent for an unknown period, and then, at a later date, go on to produce Kaposi's sarcoma, an opportunistic infection, a so-called auto-immune disorder, or any combination of these.
Further, no one is certain that the immune disorder can be reversed. Many patients have survived a bout of pneumonia or other illness, only to succumb to another or to go on to develop Kaposi's sarcoma or some other fatal cancer. 'Natural' Immunity Suppressor..."