Here’s a graphic from Birmingham university that I saved (to share with my HLH Facebook support group) -
The weird thing is that previously HLH has been rare, but far more common in children - it’s divided into two groups, primary (aka familial, inherited, or genetic) and secondary (aka acquired) with primary usually being diagnosed in babies. Lately, doctors have started to think of the two types as a spectrum rather than two distinct groups.
Secondary HLH in adults usually has a malignant trigger (mostly Leukemias and Lymphomas). It’s rare enough that in the US, most adults with it have their treatment supervised by one of the two paediatric treatment centres (Cincinnati Children’s Hospital and Texas Children’s Hospital).
The question amongst all of us in the HLH survivor/parent support group, as I’m sure you can imagine, is why is this triggering a similar condition to HLH, but almost exclusively in adults?
I have seen UK doctors on Twitter saying that all critical admissions for COVID19 are being screened for HLH/cytokine storm by testing ferritin levels. These are usually between 12-300 but can go absolutely bonkers in HLH (60,000 to 90,000 being common in HLH kids). It’s not a proper diagnosis (my DD’s diagnosis was confirmed by bone marrow aspiration which probably isn’t practical/safe in the current situation) but ferritin is good, cheap, screen and enough to start speculative treatment. HLH progresses to complete organ failure very rapidly, so prompt diagnosis and treatment is vital.
sHLH can be triggered by all kinds of things but the most common trigger is EBV - 95% of the world has had Epstein Barr Virus, most of us won’t have noticed it being anything other than a cold type virus, but in teenagers it can cause glandular fever, and in some cases, it goes on to cause cancer: www.cancerresearchuk.org/about-cancer/causes-of-cancer/infections-eg-hpv-and-cancer/does-ebv-cause-cancer
I try not to speculate re: COVID peaks and curves and death rates etc, but it’s hard not to worry if some of these mild COVID19 cases will go on to cause a massive uptick in some cancers in ten or 20 years time.