Table I.

Most common conditions leading to pachymeningitis – diagnostic differentiation

	Most characteristic organ involvement	CNS features apart from HP	Histopathological findings in dura mater	Laboratory specific findings or supportive diagnostic tests	Therapy
GPA	ENT, lungs, kidney	Cranial neuropathy, ophthalmoplegia, cerebrovascular events	Necrotizing epithelioid granuloma	ANCA (+)	GKS, CYC, AZA, MMF MTX, RTX
Sarcoidosis	Lungs, hilar adenopathy	Facial nerve palsy, leptomeningitis mass lesions	Noncaseating epithelioid granuloma	ACE 1,25 OH D3	GKS, CYC, TNFi, RTX
Infectious meningitis	CNS	Encephalopathy, seizures	Inflammatory cell infiltration with neutrophils predominance	CSF analysis, urine and blood culture	Antibiotics, tuberculostatic and antifungal agents
Erd-heim-Chester disease	Skeletal, heart, aorta	Hypophysitis cerebellar dysfunction	Xanthogranuloma with foamy histiocytes	BRAF gene mutation	Vemurafenib, GKS
IgG4-related disease	Pancreas, sali-vary gland	Orbital pseudotumor, cranial neuropathies	Lymphoplasmacytic infiltrates with IgG4 cell predominance, storiform fibrosis, and obliter-ative phlebitis	Serum IgG4	GKS, AZA, MMF, RTX
Idiopathic pachymeningitis	Absence	Cranial neuropa-thies, cerebellar dysfunction	Lymphoplasmacytic infiltrates with fibrous proliferation	Absence	GKS, RTX

TNFi – TNFinhibitors; MTX- methotrexate; CYC- cyclophosphamide; GKS- glucocorticosteroids; AZA – azathioprine; ENT- ear-nose--throat; CNS – central nervous system, ANCA – antineutrophil cytoplasmic antibodies; RTX – rituximab; ACE – angiotensin converting enzyme; CSF- cerebrospinal fluid; MMF- mycophenolate mofetil