ANCA-associated and other childhood vasculitides — branching viva

Opening question

A 14-year-old boy presents with three weeks of bloody nasal discharge, a septal ulcer, a productive cough, and cola-coloured urine. His creatinine is rising, his urinalysis shows blood and protein with red-cell casts, and his PR3 (c-ANCA) is positive. Name the diagnosis, classify the childhood vasculitides by vessel size using the Chapel Hill 2012 nomenclature, and state what makes this the pulmonary-renal syndrome. [1][7]

Branch 1 — the pauci-immune mechanism and the induction and maintenance framework

The diagnosis is confirmed. Explain the pauci-immune mechanism, state the remission-induction regimen for this organ and life-threatening disease, and justify the maintenance therapy. Why is the induction started early, even before the biopsy, in this scenario? [3][6]

Branch 2 — the absent pulse and hypertension of Takayasu arteritis

The boy instead re-presents with an absent radial pulse, a blood-pressure discrepancy between the limbs, and a subclavian bruit. How does this change the vessel size and the diagnosis, what is the mandatory investigation, and how is the disease managed with the glucocorticoid, the biologic and the revascularisation? [9]

Branch 3 — the asthma, eosinophilia and mononeuritis multiplex of EGPA

The boy instead has a two-year history of severe asthma, a marked eosinophilia, and a new mononeuritis multiplex. Name the diagnosis, explain why the troponin and the echocardiogram are essential, and state the management and the leading cause of death. [5][6]

Branch 4 — the Kawasaki cross-link

A 4-year-old presents with six days of fever, conjunctivitis, a strawberry tongue and extremity changes. How does Kawasaki disease differ in vessel size and ANCA from the ANCA-associated vasculitides, what is the treatment, and why does a positive ANCA in this phenotype argue against Kawasaki disease? [8][10]

Closing — coordination and the long-term outcome

In one sentence, what determines the long-term outcome of the ANCA-associated vasculitides and the Takayasu arteritis, and why does the general paediatrician sit at the centre of the recognition, the induction, the maintenance and the transition to the adult care? [6][9]