BackgroundUndifferentiated connective tissue disease (UCTD) is widely considered to be a distinct clinical entity, and now divided into two subgroups: stable UCTD and early UCTD. The most frequent onset symptoms of UCTD include arthralgias, arthritis, Raynaud’s phenomenon, mucocutaneous involvement, and sicca symptoms. However, Neurologic involvement is rare, and intracranial lesion as onset symptom in a patient with early UCTD has not yet been reported.Case presentationA 51-year-old Chinese female experienced progressive left leg weakness for 14 days before hospitalizing in our department. The lesion on right parietal lobe was initially detected by brain magnetic resonance imaging. Although the patient declined a cerebral biopsy, the possibility of stroke, cerebral venous sinus thrombosis, NMOSD, MS, autoimmune encephalitis, intracranial infections, and malignant tumors as cause of the lesion was excluded by intracranial angiogram, CSF study, MRI enhancement and MRS examination. Moreover, immunologic studies showed high titer of antinuclear antibody, increased erythrocyte sedimentation rate and C-reactive protein. These results led to a diagnosis of early UCTD with central nerve system (CNS) involvement. After low dose corticosteroid and azathioprine therapy, the patient’s symptoms, abnormalities in immunologic tests and cerebral radiologic examinations were all greatly improved within a short duration.ConclusionsThis is the first report of intracranial lesion as onset symptom in a patient with early UCTD. Our case suggested that central nerve system (CNS) involvement could be the onset symptom in early UCTD, and should be recognized quickly with exclusion of other causative factors in the differential diagnosis. Prompt and adequate treatment with low-dose steroid and immunosuppressive drugs could improve the prognosis of both early UCTD and CNS involvement.Electronic supplementary materialThe online version of this article (doi:10.1186/s12883-017-0868-4) contains supplementary material, which is available to authorized users.