A mutation can hide for decades, waiting for the right moment to be found.
Em oito anos de busca silenciosa por entre meio milhão de amostras de sangue, pesquisadores tailandeses encontraram o que a ciência ainda não havia nomeado: um tipo sanguíneo tão raro que apenas três pessoas o carregam em todo o conjunto estudado. A descoberta, feita na Universidade Mahidol, revela uma variação inédita do fenótipo B(A) — um híbrido enzimático que engana os testes convencionais e permaneceu invisível por décadas. É um lembrete de que mesmo os sistemas biológicos que julgamos bem mapeados guardam, nas margens, segredos que só a paciência científica consegue revelar.
- Testes de tipagem sanguínea começaram a retornar resultados contraditórios em bancos de sangue tailandeses, sinalizando uma anomalia que não se encaixava em nenhuma categoria conhecida.
- Três amostras entre 554 mil apresentavam enzimas com comportamento híbrido — tecnicamente tipo B, mas com atividade parcial do tipo A, criando um disfarce imunológico capaz de confundir tanto testes diretos quanto reversos.
- A variação nunca havia sido catalogada em nenhuma base de dados genética internacional, tornando este fenótipo B(A) mutante uma descoberta absolutamente inédita na imunogenética mundial.
- Para a medicina transfusional, o achado é urgente: uma pessoa com esse tipo sanguíneo poderia ser classificada erroneamente e receber sangue incompatível em uma transfusão de emergência.
- A descoberta amplia a compreensão de que o sistema ABO contém variações ainda desconhecidas, especialmente em populações menos estudadas, onde mutações podem persistir silenciosamente por gerações.
Oito anos. Mais de meio milhão de amostras de sangue. E, ao final, três pessoas cujo sangue se comportava de um modo que a ciência ainda não havia descrito.
Pesquisadores da Universidade Mahidol, na Tailândia, identificaram uma variação inédita do fenótipo B(A) — um tipo sanguíneo tão raro que nunca havia sido catalogado em nenhuma base de dados genética internacional. A investigação, publicada na revista Transfusion and Apheresis Science, começou com uma pergunta aparentemente simples: por que alguns testes de tipagem ABO estavam produzindo resultados contraditórios em bancos de sangue?
A resposta estava escondida em três amostras que desafiavam a lógica convencional. O sangue dessas pessoas era tecnicamente do tipo B, mas suas enzimas apresentavam atividade parcial característica do tipo A — um comportamento híbrido que enganava simultaneamente os testes diretos e reversos de tipagem. A mutação havia alterado a enzima responsável pela adição de antígenos nas hemácias, fazendo-a agir de forma incompleta e ambígua, como um sinal que os testes não conseguiam interpretar com clareza.
O que torna a descoberta especialmente significativa é a invisibilidade que a precedeu. O fenótipo B(A) já é considerado raro globalmente, mas essa variação específica nunca havia sido identificada. Entre 554 mil amostras, apenas três pessoas a carregavam — uma proporção que ilustra com precisão como variações genéticas podem permanecer ocultas por décadas, especialmente em populações menos estudadas. Mutações assim podem atravessar gerações sem causar crises médicas, sem despertar investigações, esperando silenciosamente pela escala e atenção científica necessárias para serem reconhecidas.
As implicações práticas são concretas. Uma pessoa com esse tipo sanguíneo poderia ser classificada incorretamente em uma triagem padrão, com risco real de receber sangue incompatível em uma transfusão. A descoberta oferece à medicina transfusional uma nova categoria a vigiar — e lembra que a diversidade genética humana ainda reserva surpresas, mesmo nos sistemas que acreditávamos conhecer por completo.
Eight years. Half a million blood samples. Three people whose blood behaved in a way that shouldn't have been possible.
Researchers at Mahidol University in Thailand have identified a blood type so rare that it exists in the medical literature as a single entry—a genetic variation of the B(A) phenotype that had never been cataloged anywhere in the world. The discovery, published in Transfusion and Apheresis Science, emerged from a methodical hunt through 554,000 samples, a search that began with a simple puzzle: why were some blood tests giving contradictory results?
The investigation started conventionally enough. Scientists were trying to understand incompatibilities that appeared when direct and reverse ABO typing tests disagreed with each other in blood banks. These discrepancies are unusual enough to warrant attention, but not unusual enough to suggest something entirely new. Then three samples emerged from the dataset with readings that made no sense. The enzymes in these blood samples were behaving like a hybrid—technically type B, but with partial enzymatic activity that mimicked type A. The altered enzyme was adding antigens in a way that fooled both the direct and reverse tests, creating a kind of immunological disguise.
What makes this discovery significant is not just that it exists, but that it had remained invisible for so long. The B(A) phenotype itself is already considered rare globally. But this variant—this specific mutation—had never been identified before, never documented in any international genetic database. Among 554,000 samples, only three people carried it. That ratio speaks to how easily genetic variations can hide in plain sight, especially in smaller or less-studied populations. Geneticists note that mutations like this one can remain dormant and undetected for decades, waiting for the right combination of circumstances—a large enough sample size, the right testing methodology, the right moment of scientific attention—to be recognized.
The blood itself tells an interesting story about how the ABO system works. The gene that determines blood type produces enzymes that add specific antigens to red blood cells. In type A blood, one enzyme adds A antigens. In type B blood, a different enzyme adds B antigens. In this newly discovered variant, the mutation had altered the enzyme in a way that made it add antigens only partially, creating a phenotype that was neither fully B nor fully A, but something in between. This hybrid behavior is what made the blood confusing to standard typing tests—the tests were looking for clear signals, and instead they were getting ambiguous ones.
The discovery expands what researchers understand about how much variation the ABO system can actually contain. For decades, blood typing has been treated as a relatively straightforward classification: A, B, AB, or O. But the Thai research suggests that within those categories, there are subtypes and variations that remain unknown, particularly in populations that have not been extensively studied or screened. A mutation can persist undetected in a family or community for generations, never causing a medical crisis, never triggering the kind of investigation that would bring it to light. It takes a large-scale screening project, careful attention to anomalies, and the willingness to follow a thread for eight years to find what was always there.
For blood banks and transfusion medicine, the practical implications are real. A person with this blood type would need specially matched blood for a transfusion. Standard typing would likely misclassify them, potentially creating a dangerous mismatch. The discovery means that medical professionals now have a new category to watch for, a new reason to investigate when test results don't align. It also means that somewhere in Thailand, three people now have a medical record that acknowledges something genuinely unique about their biology—a reminder that human genetic diversity still contains surprises, even in systems we thought we understood completely.
Citas Notables
The altered enzyme adds antigens in a way that fools both direct and reverse tests, creating a kind of immunological disguise.— Mahidol University research findings
La Conversación del Hearth Otra perspectiva de la historia
Why did it take eight years to find something that exists in only three people?
Because you're looking at 554,000 samples. The rarity is the point. If it were common, it would have been found decades ago. You need scale and patience and the right moment when someone notices the anomaly.
But the tests were already failing. Shouldn't that have been a red flag earlier?
It was a red flag, but not necessarily the kind that screams "new blood type." Incompatibilities in ABO testing happen for various reasons. You have to be willing to dig deeper, to ask whether the test is wrong or whether the blood is telling you something new.
These three people—do they know they're unique?
They do now. They're in the medical literature. But they probably went their whole lives without knowing their blood was unusual. It only mattered when they needed a transfusion or when they happened to be part of a research sample.
Could there be more people out there with this blood type who haven't been tested?
Almost certainly. This variant was found in Thailand. There could be others in other populations, in communities that haven't been screened at this scale. The discovery is less about finding the only three people and more about understanding that these variations exist and can hide for a very long time.
What changes now for blood banks?
They have to add this to their awareness. When tests don't match up, they can't just assume human error anymore. They have to consider that the blood itself might be telling them something they've never seen before.