Question 1

Almost 99% of the sickle cell patients I see in clinical practice cannot afford curative treatment options. How can I best improve quality of life for these patients?

Dr. Arun Singh Danewa · Accepted Answer

Hydroxyurea should be given to every single patient, along with L-glutamine: these are the two proven medications that are effective in sickle cell anaemia, and further drugs are in trials. Vaccination, especially against Haemophilus influenzae, pneumococcus and Neisseria meningitidis, should be part of every patient's programme. In children, transcranial Doppler screening is very important: if the reading crosses the cutoff, chronic transfusion therapy should be started to prevent a first stroke, and a patient who has already had a stroke needs chronic transfusion therapy regardless. Patients should also be educated about the precipitating factors of a pain crisis, such as changes in weather and infection.

Question 2

If disease-modifying drugs continue to improve, will that eventually eliminate the need for bone marrow transplant?

Dr. Arun Singh Danewa · Accepted Answer

No. These drugs do not hit the primary pathology, the sickling process itself. They can reduce pain symptoms and severity, but the silent chronic organ damage keeps progressing underneath. Only bone marrow transplant and gene therapy correct the underlying disease, so a patient who can access and afford curative therapy should pursue it; supportive therapy remains the best option only where curative treatment is out of reach.

Question 3

Over a lifetime, would supportive therapy end up costing more than a bone marrow transplant?

Dr. Arun Singh Danewa · Accepted Answer

The cumulative cost is similar. I have seen many patients aged 34 or 36 say they will accept any risk of transplant just to be rid of the disease, because they are fed up. If hospitalizations and drugs are added together, the total cost is similar to that of a bone marrow transplant. The difference is that transplant needs the money at one time, in a short span, while supportive care is paid in smaller instalments that are less visible.

Question 4

How many times can one person be a bone marrow donor, and after how long can they donate again?

Dr. Arun Singh Danewa · Accepted Answer

Blood bank regulations differ from country to country, but a donor can usually donate a maximum of two times. The minimum gap between two donations should be six months; six months to a year is preferred, and in a life-threatening situation it can very rarely be done at three or four months. In most Indian settings, donation is not permitted after two donations, so a donor can donate twice in their lifetime.

Question 5

If two siblings both have sickle cell disease and one sibling is a full-match donor, can that one donor's harvest be used for both patients?

Dr. Arun Singh Danewa · Accepted Answer

Yes, this is done in practice. Since the minimum stem cell dose is 3 million cells per kilogram of the recipient's weight, a larger harvest can be divided into two doses for two patients. Where families want to proceed with one transplant first and the second once funds are arranged, half the dose is used immediately and the rest is cryopreserved for the second transplant later, sometimes with additional stimulating injections used to boost the donor's total yield.

Question 6

Why cryopreserve stem cells rather than simply asking the donor to donate again later?

Dr. Arun Singh Danewa · Accepted Answer

Collected stem cells only survive about 72 hours at refrigerator temperature, 2 to 8 degrees, before they die. Cryopreservation stores them at minus 80 to minus 90 degrees, where they remain viable for about a year, the same technique used for sperm banking or oocyte preservation. This means a single donation is sufficient if enough dose is collected upfront, and the donor does not need to return for a second transplant planned months later.

Question 7

If a patient undergoes a successful bone marrow transplant, grows up, and has children of their own, is the sickle cell inheritance chain broken for the next generation?

Dr. Arun Singh Danewa · Accepted Answer

No. Transplant replaces the hematopoietic stem cell system, not the gene: the reproductive organs still carry the SS gene, so the patient will transmit one sickle gene to every child. If the partner is unaffected, the children will be carriers. If the partner is also a carrier and passes on a sickle gene, the child can again have sickle cell disease. It is therefore important to educate families that after a successful transplant, when the patient grows up and wants to have children, the partner should be tested for sickle cell.

Question 8

Infertility and sexual dysfunction are different things. If a child who underwent transplant grows up to be infertile, will he also have sexual dysfunction?

Dr. Arun Singh Danewa · Accepted Answer

Sickle cell is a double-edged sword. Before transplant, the disease itself affects the reproductive organs, just as it affects the chest and kidneys. One known complication is priapism: during a sickle crisis the penis can remain erect, and if this lasts four hours it can cause lifelong erectile dysfunction. In girls, repeated sickling episodes affecting the ovaries can cause infertility. After transplant, busulfan destroys the sperm-producing cells as well as the cells that support them, which reduces testosterone, so these children may not attain puberty properly. With newer drugs the chances are very low, but sexual dysfunction, not only infertility, can occur after transplant. This should be an integral part of transplant counseling: for adolescent patients, families should consider sperm banking or oocyte preservation before coming for transplant.

Question 9

Is it safe to do a bone marrow transplant in a child between one and two years old, when they cannot yet express symptoms during the process, or is it better to wait until they can?

Dr. Arun Singh Danewa · Accepted Answer

One year is the age given in the literature, though I would prefer to transplant by two years of age. The child's inability to express symptoms is not an issue: in leukaemia and other do-or-die situations, transplants are done even at six or eight months or one year. What matters is that the body can handle the immunosuppression, the drugs and the heavy toll of the transplant, which requires more mature organs. So transplant can be done at one year, but the preferable age is two to five years, when the outcome is excellent.

Question 10

What are the chances of a sickle cell carrier experiencing a crisis?

Dr. Arun Singh Danewa · Accepted Answer

Extreme changes in environment can sometimes precipitate symptoms even in a carrier, for example going to high altitude in the mountains without acclimatisation. Stress, infection and cold temperature, which causes vasoconstriction, can also precipitate symptoms. Carriers have less than 50% sickle haemoglobin, typically about 35 to 40%, so they can have mild to moderate symptoms, but the severity is much lower than in a sickle cell patient and is not as concerning as the disease itself. The same logic applies after transplant: the book figure for the chimerism needed in sickle cell is only 12%, and in our experience, if even 25% of donor cells are working after one, two or five years, the patient will not have sickle symptoms. Carriers, with about 35 to 40% sickle haemoglobin, likewise have no symptoms except in very extreme situations.

Question 11

What chimerism percentages do you look for after transplant, starting at day 30, and what do you do if chimerism is below the target?

Dr. Arun Singh Danewa · Accepted Answer

By definition, chimerism above 95% is full donor chimerism, anything between 5% and 95% is mixed chimerism, and anything below 5% is graft failure. At day 30 we want 95%. The real target, however, is stable chimerism rather than 95%: if chimerism is at 50% at six months but is not going down, that is stable mixed chimerism, and the body has accepted the donor cells. In thalassaemia at least 80 to 85% is needed, but in sickle cell a stable level between 25% and 95% is acceptable. Ten years after transplant a sickle cell patient may have only 50% chimerism and still have no symptoms. The 25% figure is my personal experience; some reports suggest as low as 12% is sufficient. What matters early is stability, because when chimerism is 70% at day 30 it often falls quickly to 5% and the donor cells are rejected.

If chimerism at day 30 is below target, say 80% or 75%, the first step is to reduce the drugs given after transplant to prevent GVHD, such as cyclosporine and tacrolimus, because they suppress the donor cells, and recheck chimerism after two weeks. If it comes up, we resume at a reduced dose. If it keeps falling, the next method is donor lymphocyte infusion (DLI), a calculated dose of the donor's peripheral blood. We sometimes prepare a DLI aliquot at the time of harvest and cryopreserve it; otherwise the donor may need to be called back. If chimerism still falls below 5% after these two methods, a second transplant is the only way to overcome graft failure.

Question 12

How rare are these complications? Out of 100 transplants, how many proceed without complications or with manageable ones, and how many are a real worry?

Dr. Arun Singh Danewa · Accepted Answer

The answer lies in the hierarchy of donor selection. The best choice is a matched sibling. With a full-match brother or sister, the chances of graft failure and GVHD are minimal and easily handled; graft failure occurs in only 3 to 5%. With a matched unrelated donor or a haploidentical donor, the risk of graft failure is a little higher, around 5 to 8% in the literature and in my experience, provided a good conditioning regimen is used to eradicate the sickle bone marrow, cyclosporine and tacrolimus levels are tightly monitored, chimerism is checked at defined time points, and intervention is early.

Question 13

Is there a test that can be done while a mother is pregnant to know the sickle cell status of the baby before birth?

Dr. Arun Singh Danewa · Accepted Answer

Yes. Where both partners are known sickle cell carriers, chorionic villus sampling at 10 to 13 weeks of pregnancy is the ideal method, telling the family whether the baby is AA, AS, or SS. Amniocentesis from 15 weeks is the alternative, and cordocentesis at 18 to 20 weeks is a further option but carries a higher complication rate, which is why testing earlier in pregnancy is preferred. What happens with that information depends on the country's laws on termination and the family's own wishes.

Question 14

Can you explain the immunological basis of graft rejection after a haploidentical transplant?

Dr. Arun Singh Danewa · Accepted Answer

There are two mechanisms. Antibody-mediated rejection happens when repeated blood transfusions leave a patient with donor-specific antibodies; if these are high, the graft is rejected outright and neutrophil engraftment never occurs, which is why a negative DSA result is mandatory before a haploidentical transplant, with desensitization required first if it is positive. Cell-mediated rejection happens when conditioning chemotherapy fails to fully eliminate the patient's own bone marrow, leaving residual recipient cells that reject the donor's stem cells. Preventing graft failure means confirming a negative DSA and using a sufficiently intense conditioning regimen.

Question 15

How do you manage a sickle cell patient who is also HIV-positive, and can the transplant address the HIV as well?

Dr. Arun Singh Danewa · Accepted Answer

There is no contraindication to transplanting a sickle cell patient who is HIV-positive. The first requirement is that the donor is HIV-negative, which is checked through viral markers in the pre-transplant evaluation. HIV resides in the CD4 lymphocytes; conditioning chemotherapy reduces the patient's lymphocytes, but the virus persists in hidden reservoirs and can infect the new donor cells, so antiretroviral therapy must continue through and after transplant. The few reported cures of HIV after bone marrow transplant used donors carrying a rare CCR5 mutation that makes cells resistant to HIV. It is not the standard of care, and there is no indication to transplant for HIV alone.

Question 16

In case of graft rejection, when can a bone marrow transplant be done again, and can the same donor be used?

Dr. Arun Singh Danewa · Accepted Answer

It depends on the patient's condition. Sickle cell is a benign disease and not immediately life-threatening, so for benign conditions such as thalassemia and sickle cell disease my advice after graft failure is to wait, ideally a year, and give the body time to recover from the previous transplant; six months to a year is sufficient, because transplant itself is a very complicated process. Some centres retransplant within three months, and there is no absolute contraindication. In leukaemia, by contrast, the second transplant has to be done immediately. A donor can donate twice in a lifetime, so the same donor can be used again: if the first transplant used a full-match sibling and the graft failed, I would still prefer that full-match donor over a half-match donor and collect stem cells from them again, with the necessary precautions. The donor can also be changed: one of our patients whose graft from his mother failed returned two years later, and we found a matched unrelated donor for his second transplant.

Question 17

On the age cutoff for transplant, one colleague argues that existing organ damage should matter more than age itself, so even a 35-year-old with preserved organ function would be attempted, while a 15-year-old with multi-organ damage would not. What is your view?

Dr. Arun Singh Danewa · Accepted Answer

That view is correct. Age becomes a factor only because of the organ damage that accumulates alongside it, so a patient with well-preserved organs despite their age should not be disqualified, and a full-match sibling donor with good organ function can support a transplant well into a patient's thirties. Haploidentical transplant in older patients is approached more cautiously, since complications run higher there specifically. Counseling has to be transparent regardless of age, walking families through expected complications and risks based on a comprehensive pre-transplant evaluation, since organ damage is sometimes more advanced than a patient realizes.

Question 18

After the one-year mark, with chimerism doing well, will further sickling episodes occur, and will organ damage from before the transplant reverse?

Dr. Arun Singh Danewa · Accepted Answer

If chimerism is at an adequate, stable level, no further sickling will occur; this is an all-or-none outcome once stable chimerism is achieved, not something that happens intermittently. However, damage that occurred before transplant, such as disability from a prior stroke, does not reverse; the transplant stops further damage rather than undoing what has already happened. After the one-year mark with good chimerism, the chance of graft failure is under 5%, and after two to three years it is close to zero, so cure in this context means no further sickling and no further organ damage, not an undoing of pre-existing injury.

Live Discussion with Dr. Arun Singh Danewa