Granulomatosis with Polyangiitis Presenting with Pyoderma Gangrenosum-Like Ulceration and Negative Cytoplasmic Antineutrophilic Cytoplasmic Antibodies in a Child.

Granulomatosis with polyangiitis (GPA), a vasculitis that most commonly affects small to medium-size vessels of the respiratory tract and kidneys, may also present with a wide array of skin findings. We present the case of a 12-year-old boy with pyoderma gangrenosum-like ulcerations on his lower extremity as the initial manifestation of GPA despite negative cytoplasmic antineutrophilic cytoplasmic antibodies (c-ANCAs). Although GPA is strongly associated with c-ANCA, c-ANCA may be negative on presentation. Thus clinical and pathologic clues must be relied upon when serologic confirmation is negative.