Aicardi-Goutières syndrome is a rare progressive encephalopathy characterized by a typical clinical picture, bilateral basal ganglia calcifications, leukodystrophy and brain atrophy, lymphocytosis, and elevated interferon-alpha in the cerebrospinal fluid. Among the cases described to date, variability in the clinical expression or in the cerebrospinal fluid abnormalities has been reported. We present a case with a delayed diagnosis at the age of 8 years, when brain computed tomography was done because there was no first image from the age of 8 months, when the disease started. Symmetric basal ganglia calcifications were visualized and led to purposeful investigation of the cerebrospinal fluid. It revealed an interferon-alpha titer of 103 IU/mL, which, together with the progressive brain damage and disease course, was crucial for the diagnosis. This rare finding of long-term highly elevated interferon-alpha in the cerebrospinal fluid is discussed with respect to the clinical course.