Orbital pseudotumor and skull base infiltration as the sole manifestation of granulomatosis with polyangiitis.

Granulomatosis with polyangiitis (GPA) is a vasculitis affecting small and medium-sized blood vessels. It typically presents with upper respiratory tract, lung, and kidney involvement. However, the disease may involve multiple other organs, and not all cases present with these classic manifestations. Periocular lesions are described in the GPA and, especially in the case of isolated, single-site disease, require extensive differentiation from other diseases, such as IgG4-related disease or myofibroblastic tumor. However, periocular lesions and coexisting symptoms suggesting changes in the central nervous system without other organ changes are undoubtedly a diagnostic challenge. Such situations are described in the literature mainly as case reports, not as a rule in connection with GPA. The impetus for writing this article and analyzing the literature was a case of GPA manifesting as infiltration of the skull base presenting as multiple cranial nerve palsies. A review of atypical cases of GPA in the literature suggests that skull-based involvement is an important yet easily overlooked presentation. Through this case-based review, we aim to raise awareness that GPA may present with isolated cranial nerve palsies.