Back in 1972 when I was still a trainee hematologist, my boss, Jeremy Lee Potter, told me that leg cramps were a feature of CLL. I couldn't find any data to establish this so I set about collecting my own. Sure enough, several of my patients complained about leg cramps, although lots of them denied ever having had a leg cramp. Some said that they had never had leg cramps before they had been diagnosed with CLL.
Of course, no study is complete without a control population, so I set about asking other people with hematological diseases of the same age, as well as patients admitted to hospital for routine surgery if they had leg cramps. Unfortunately, it soon transpired that lots of other people had leg cramps too, and I was never going to assemble a large enough population to establish whether or not there was a statistically significant difference in incidence.
I had some ideas about why patients had leg cramps, largely surrounding the enlarged spleen - patients with splenomegaly are known to get ischemic leg ulcers - but I couldn't make it stick.
I explored treatment too, including magnets under the mattress and soap on the sheets, but the one thing that always worked was quinine 200mg at night. I prescribed this for 30 years without mishap, but lately the pharmacologists have advised against it because of the rare occurrence of quinine induced immune thrombocytopenia. The reckon that leg cramps are not severe enough to warrant the tiny risk. I tend to ignore them.