Understanding Hairy Cell Leukemia: Presentations and Complications

At the Hairy Cell Leukemia Foundation 2025 Conference in Bologna, Italy, we had the opportunity to sit down with Dr. Dima El-Sharkawi for a live interview. The discussion focused on how hairy cell leukemia typically presents in patients and the challenges clinicians face in identifying the disease early.

During the interview, El-Sharkawi also explored some of the rarer patterns of the disease, including unusual presentations with high white blood cell counts and potential complications involving the central nervous system.

Currently, El-Sharkawi serves as a consultant hematologist at the Royal Marsden NHS Foundation Trust Hospital, located in London, England.

Transcript

Can you describe how hairy cell leukemia typically presents in patients, and are there any rare or unusual patterns that clinicians should be aware of?

For most patients with hairy cell leukemia, when they present, it's with the symptoms of low blood counts. And actually, when you look down the microscope at the blood film to see all the cells, unless you're specifically looking for the hairy cells, there aren't many in the blood, so it's hard to see. In rare cases, for patients with hairy cell leukemia, as well as getting a reduction of the normal blood cells, you can see quite a lot of the hairy cells, so the abnormal leukemia cells coming out of the bone marrow and into the blood. So the white cell count can be quite high because of this.

Now, this is very unusual, so for most patients, the hairy cell leukemia stays in the bone marrow, and very little of it comes out into the blood. But we do know a small proportion of people can have what we call, in medical terms, hyperleukocytosis, so a high white count related to it. There have been some case reports published about patients with this hyperleukocytosis, and there is a suggestion that those patients often don't have as long a response to the standard treatments. I've presented a case, and there are other cases that have been presented at other similar conferences and also published in medical journals, detailing the outcomes of some of these patients with high white cells.

As with a lot of our diseases that we treat, we end up treating all patients in the same way, but we know that some patients' disease is going to come back much quicker than with other patients. We try and work out, based on genetic mutations or different features about their disease, if we can predict which patients are more likely to have a shorter time until their disease comes back. For hairy cell leukemia, one of these things may be having a high white cell count.

The other thing that we have seen, and others have seen, is that perhaps there's a slightly higher risk of a rare complication where the hairy cells not only go to the blood but that they may enter the central nervous system. So that's either affecting the brain or the fluid or the layers surrounding the brain and the spinal cord, and that can lead to symptoms like headaches, visual disturbances and dizziness.

When we think about treatments in that context, we need to think about treatments that are going to treat the hairy cell leukemia, but also cross what we call a blood-brain barrier, so to get to the area where we need it to go to treat the disease that's in the central nervous system. As I said, it is a very rare complication of hairy cell leukemia, so very little is known about the best way of treating it, but there is evidence that some of the standard treatments that we use, such as BRAF inhibitors, such as BTK inhibitors, that we know work for hairy cell leukemia, we also know cross this blood-brain barrier and so potentially could have efficacy in those circumstances.

Transcript has been edited for clarity and conciseness.

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