A Ferritin of 14,500 Changes What “First-Line” Should Mean in Adult-Onset Still’s
The textbook approach starts with steroids and reserves biologics for treatment failure. Her ferritin is high enough that waiting to fail steroids first is its own real risk.
Ana Maria V., a 29-year-old graduate student in urban planning, came to the emergency department after ten days of daily fever spiking to 39.5-40°C each evening, an evanescent salmon-pink rash across her trunk that her roommate noticed came and went with the fever itself, and pain and swelling in both wrists and knees that had made typing for her thesis increasingly difficult. She had also had an unexplained sore throat early in the illness that resolved on its own — a detail that, taken with the fever pattern and rash, fits the classic Still's disease triad rather than a straightforward infectious pharyngitis. An extensive infectious workup, including blood cultures, viral serologies, and a throat culture, has come back entirely negative, and imaging has shown no lymphadenopathy or organomegaly suggestive of a lymphoproliferative process — both real, necessary exclusions before a diagnosis this reliant on ruling other things out can be accepted.
Her inflammatory markers are strikingly abnormal: ESR over 100, CRP above 200, and a ferritin that returned at 14,500 ng/mL, a level far beyond what her fever and rash alone would typically produce. She does not, as of this morning's labs, meet full criteria for MAS itself — her platelet count and fibrinogen remain within normal range, and she has no evidence of hepatic dysfunction or hemophagocytosis on the peripheral smear reviewed today — but the 2016 EULAR/ACR/PRINTO criteria set their ferritin threshold for macrophage activation syndrome at 684 ng/mL, and she sits more than twenty times above it while meeting none of the four supporting criteria. One element overshot enormously, the rest not met at all, is not the pattern those criteria were built to classify. Meeting Yamaguchi's criteria settles what disease this is; nothing in front of the team settles how fast it is moving, because no threshold anyone has published says what a ferritin of 14,500 predicts over the next forty-eight hours.
How urgently the first dose needs to move
A ferritin of 14,500 is not just a severe lab value — the 2016 EULAR/ACR/PRINTO macrophage activation syndrome criteria set their ferritin threshold at 684, and she is more than twenty times above it. I'd start anakinra now, as initial therapy rather than after a steroid trial, precisely because it works within days, and I don't want to spend those days finding out the traditional stepwise approach was too slow for this particular ferritin.
I'd point out that a genuine subset of Still's disease responds fully to high-dose glucocorticoids alone, and steroids can be started this hour with no access delay, unlike a newly initiated biologic. Cavalli and colleagues describe anakinra as the cornerstone of biologic therapy in this disease, but that's a statement about which biologic to reach for once one is needed — not proof that biologic therapy is needed as the first move for every new diagnosis.
Her ferritin is real and I'm not dismissing it, but she doesn't meet MAS criteria this morning — platelets and fibrinogen are both normal. I'd start steroids first and reserve anakinra for a steroid-refractory course or any sign of MAS actually evolving.
I don't think this needs to be steroids-then-see, or biologic-instead-of-steroids. Anakinra's onset is fast enough that starting it alongside high-dose glucocorticoids today costs very little if steroids alone would have been enough — but if her ferritin trajectory is heading toward MAS, waiting to find that out sequentially is the genuinely higher-risk choice.
I'd start both now, not because every new Still's diagnosis needs this, but because this specific ferritin does. If she settles quickly, anakinra can be tapered off just as fast as it was started.
High-dose glucocorticoids and anakinra were started together that day, with daily ferritin, platelet count, and fibrinogen monitoring specifically to watch for any evolution toward frank MAS criteria rather than assuming the combination had eliminated that risk.
Not agreed: whether this combined-initiation approach should become her team's default for future new Still's diagnoses that present with a less dramatically elevated ferritin. The Clinical Pharmacologist was explicit that today's decision was proportionate to this specific lab value, not a new general policy; the Hematologist remains committed to the traditional stepwise approach for a patient presenting with a more moderate ferritin elevation, while the Rheumatologist was less certain a lower threshold wouldn't still warrant the same urgency. All three agreed the question was worth revisiting on the next case, not resolved by this one.