Idiopathic hypertrophic pachymeningitis presenting with a superficial soft tissue mass

Idiopathic hypertrophic pachymeningitis (IHP) is a chronic progressive diffuse inflammatory fibrosis of the dura-mater, leading to its diffuse enlargement. The following describes a case of IHP presenting with a superficial soft tissue mass. A 40-year-old female came to hospital with a subcutaneous lump over the left face and frontal headache for 6 months. An excision biopsy revealed chronic inflammation. Magnetic resonance imaging (MRI) of the brain showed left mastoiditis and early dural inflammation of the left temporal region. A few months later, she developed diplopia, complex partial seizures, and retrobulbar neuritis of the left optic nerve. Repeat MRI brain demonstrated meningeal thickening on both sides of the tentorium cerebelli extending to the left tempero-parietal meninges. The meningeal biopsy revealed markedly thickened fibro-connective dural tissue with infiltration of chronic inflammatory cells. There was no evidence of bacterial, fungal, tuberculous or neoplastic infiltration. IHP was diagnosed and steroid therapy initiated. Within weeks, she showed marked clinical improvement. IHP is a diagnosis of exclusion. The absence of underlying infective, neoplastic, or systemic autoimmune disease favors IHP. The above patient had headache, neuro-ophthalmic signs, seizures, which are features of IHP. However, superficial soft tissue involvement is rare.