A Teacher's Mild Proteinuria and a Question Pediatrics Never Really Had to Answer
A single patient with new adult-onset IgA vasculitis and mild renal involvement. The disagreement is over whether to treat now, given that almost everything known about this disease's response to treatment comes from children, not adults like her.
Dana W., 42, teaches third grade and had a cold going around her classroom about ten days before the purpura appeared — tender, raised, unmistakable, spreading across both lower legs and onto her buttocks, along with joint aches and a dull ache in her stomach she initially blamed on the same virus. A skin biopsy settled the diagnosis: leukocytoclastic vasculitis with IgA deposits on direct immunofluorescence, the same disease known in children as Henoch-Schönlein purpura but renamed IgA vasculitis when it's recognized, as it increasingly is, in adults too. What's brought the team to a genuine decision point is her urine: new hematuria and a urine protein-to-creatinine ratio of 0.8, mild but real renal involvement, with her kidney function itself still normal. In children, this disease is usually self-limited and renal involvement, when it occurs, often resolves without specific treatment. Adults are a different story in ways that matter directly to her: adult-onset IgA vasculitis carries a meaningfully higher rate of progression toward chronic kidney disease than the pediatric version does, which raises the real stakes of her mild proteinuria in a way the disease's usual reputation as self-limited doesn't quite prepare a clinician for.
The trouble is that almost everything solid known about treating this disease's renal involvement comes from pediatric trials, which show more consistent benefit from glucocorticoids than the thinner, more mixed adult literature does. There is no adequately powered randomized trial testing immunosuppression in adults with her specific severity — mild, sub-nephrotic proteinuria, preserved kidney function — leaving guideline bodies to extrapolate from the closely related IgA nephropathy framework instead, principally KDIGO's. That framework treats a UPCR at her level, 0.8, as falling below the roughly 1 g/day-equivalent threshold it uses to justify adding immunosuppression, favoring supportive measures — blood pressure control, an ACE inhibitor or ARB for its own independent proteinuria-reducing effect — as the appropriate first step, with immunosuppression reserved for higher-grade or progressive proteinuria. Whether that borrowed framework, built for a related but distinct disease, is the right ruler to measure her risk against is exactly what the room doesn't have a clean answer for.
Borrowing a framework built for a different disease
Adult IgA vasculitis nephritis has a real, documented worse baseline prognosis than the pediatric disease, and I manage it much the way I manage IgA nephropathy given the real overlap between the two. I'd start an ACE inhibitor now for its own proteinuria-reducing effect, independent of any immunosuppression question, given how much higher the stakes of under-treating renal involvement are in an adult than in a child.
I'd stay conservative on immunosuppression specifically. Her proteinuria is mild and sub-nephrotic, her kidney function is entirely normal, and her skin and joint symptoms are the dominant, actively self-limited-appearing picture right now. The pediatric trials showing clear glucocorticoid benefit don't reliably extrapolate to adults, and unnecessary steroid exposure is a real cost that shouldn't be paid on evidence this thin.
I'm not disputing that adult renal outcomes are worse on average — I'm questioning whether that population-level statistic should drive treatment for a specific patient whose actual numbers today sit at the milder end of what gets measured.
There genuinely isn't an adequately powered adult trial at her exact severity tier, which means whichever choice gets made here is an extrapolation either way — the question is which framework to extrapolate from. The KDIGO IgA nephropathy framework, which shares real pathophysiology with her disease, treats a UPCR of 0.8 with preserved kidney function as below the threshold that justifies immunosuppression, favoring maximal supportive care — an ACE inhibitor or ARB and blood pressure control — first-line. That's a closer, more mechanistically related borrowed framework than either the reassuring pediatric natural history or a reflexive 'adults do worse' escalation — I'd start the ACE inhibitor, hold immunosuppression, and set an explicit proteinuria threshold that would trigger revisiting it.
Agreed: start an ACE inhibitor and supportive blood pressure management, defer immunosuppression, and set an explicit proteinuria threshold (UPCR trending above 1.0, or any decline in eGFR) that would prompt reconsidering glucocorticoids.