Aplastic anemia: the bone marrow that stops making blood, and the two roads back
Last updated September 3, 2026.
Aplastic anemia is the bone marrow failing to make enough of all three blood cell lines: red cells, white cells, and platelets. The result is the triple shortage: exhaustion and breathlessness from anemia, infections from low white cells, and bruising and bleeding from low platelets. It is rare, it can strike at any age, and it comes on over weeks to months. In most cases the cause is the immune system attacking the marrow, and for many no trigger is ever found; some cases follow viruses, medicines, chemicals, or pregnancy. Diagnosis needs a bone marrow biopsy, because the failing marrow must be seen directly. Treatment comes down to two roads: a stem cell transplant, the curative option for younger patients with a matched donor, and immunosuppressive treatment, usually horse ATG with cyclosporine and eltrombopag, which restores blood production in the majority. While counts are low, the daily disciplines are infection vigilance and bleeding precautions, and the fever rule is absolute.
What does it look like?
The three shortages produce the three symptom groups, often together: tiredness, pale skin, and breathlessness on stairs from the anemia; fevers, mouth ulcers, sore throats, and infections that linger from the white cells; and easy bruising, bleeding gums, nosebleeds, heavy periods, or pinprick red spots on the skin from the platelets. The pace is usually weeks to months of creeping symptoms rather than a sudden collapse.
Why does it happen?
In most cases the immune system mistakenly attacks the stem cells in the marrow, and in most of those cases no one ever finds why. A minority follow a virus, a medicine, chemical exposure such as benzene, or pregnancy. It is not cancer, it is not contagious, and it is not caused by diet, stress, or anything the patient did. Rare inherited forms exist, which is why younger patients get extra testing.
How is it treated?
- A stem cell transplant is the cure when it is available. For younger patients with a matched sibling donor, transplant is usually the first choice, replacing the failing marrow entirely. Siblings get tested first, and unrelated donor registries extend the search.
- Immunosuppression restores the marrow for most others. Horse ATG, cyclosporine, and eltrombopag together switch off the immune attack, and the majority respond over months. Counts recover gradually, and relapses can happen, so follow-up is long.
- Supportive care bridges the gap. Transfusions hold the red cells and platelets, and antibiotics treat infections promptly. Transfusions are used thoughtfully, because too many can complicate a future transplant.
- The fever rule is absolute. With low white cells, a temperature of 100.4 degrees F or higher is a same-hour emergency, every time, until the team says otherwise.
- Daily life gets risk-adjusted, not cancelled. Bleeding precautions: soft toothbrush, electric razor, no contact sports while platelets are low, and a medication review to remove anything that thins blood further.
When is it the emergency?
A temperature of 100.4 or higher, shaking chills, bleeding that will not stop, a severe headache, or confusion are all same-hour emergencies while counts are low. New bruising patterns or blood in urine or stool deserve same-day contact with the team. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
How serious is this?
Serious, and treatable, and both halves are equally true. Serious because your marrow is under-producing all three blood cell lines, and the shortages carry real risks: infection from the low white cells, bleeding from the low platelets, and the exhaustion of anemia. Treatable because two roads exist: a stem cell transplant, which is often curative in young patients with a matched donor, and immunosuppressive treatment, which restores blood production in the majority. The next weeks are about which road is yours, and the fever rule and bleeding precautions keep you safe while the answer is found.
What does my brother being a donor actually involve?
First, a blood test to see whether his tissue type matches yours; siblings have roughly a one-in-four chance each. If he matches, his part is usually a process much like an extended blood donation: a few days of injections to push stem cells into the bloodstream, then a collection day on a machine, and he goes home tired and fine. Your part is the bigger one: chemotherapy to clear the failing marrow, then the transplanted cells finding their way home and rebuilding your blood over weeks. A matched sibling transplant in a young patient is the best shot this condition has, which is why the hematologist reached for his name first.
What is the horse antibody treatment, and does it work?
It is called ATG, and yes, it works. The thinking is that in most aplastic anemia the immune system is attacking the marrow, so the treatment temporarily switches off the attackers: horse ATG does the heavy lifting, cyclosporine holds the line, and eltrombopag prods the marrow to produce. The majority of patients respond, with counts climbing over months, not days. It is given in hospital over a few days because reactions need watching. Relapses can happen later, which is why follow-up lasts years, and a relapse usually responds again or opens the transplant door.
Why does nobody know what caused mine?
Because in most cases there is no findable cause, and that is the honest state of the science. The mechanism is known: the immune system mistakenly attacks the marrow's stem cells. The trigger usually is not. A minority of cases follow a virus, a medicine, chemical exposure, or pregnancy, and your team will have hunted for those. The no-cause answer feels unfinished, but it changes nothing about the treatment, which targets the immune attack regardless of what started it. One certainty worth holding: it was not your diet, your stress, or anything you did.
What are the rules while my counts are low?
Two rules carry most of the weight. The fever rule: a temperature of 100.4 degrees F or higher is a same-hour emergency, every time, because your white cells cannot be trusted to contain an infection, and the teams would always rather see you early. The bleeding precautions: soft toothbrush, electric razor, no contact sports or heavy straining while platelets are low, blow your nose gently, and check with the team before any medicine, because common ones like ibuprofen thin the blood further. Around those two rules, life is risk-adjusted rather than cancelled: work, friends, and exercise in moderation are usually fine.
Will this come back after treatment?
It can, and the honest numbers are worth having. After a successful transplant, cures are usually permanent. After immunosuppression, a substantial minority relapse over the years, which is why the follow-up appointments never really end. A relapse is not a failure: it is the condition's nature, and it usually responds to another round of treatment or becomes the reason transplant moves to the front of the queue. The practical takeaway is to keep the appointments even when you feel well, because the counts change before the symptoms do, and catching a slide early is always easier.