The "eye-of-the-tiger" sign may be absent in the early stages of classic pantothenate kinase associated neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare disorder associated with brain iron accumulation. The brain MRI abnormality consists of T2 hypointensity in the globus pallidus with a small hyperintensity in its medial part, called the "eye-of-the-tiger" sign. We report on 2 patients affected by PKAN, in whom MRI examination did not demonstrate the "eye-of-the-tiger" sign in the early stages; the typical abnormalities were detected only in the following examinations. Case 1 is a 4-year-old boy first studied at age 2 years for psychomotor delay. The brain MRI was normal. In the following 2 years, the motor impairment progressed. The second brain MRI at age 4 years demonstrated the "eye-of-the-tiger" sign. Molecular analysis of the PANK2 gene revealed a missense mutation F228S in exon 2 in homozygosis. Case 2 is a 6-year-old boy first studied at age 2 years because of psychomotor delay. His brain MRI did not demonstrate abnormalities in the globus pallidus. In the following years spastic-dystonic tetraparesis became evident. A brain MRI at age 4 years demonstrated the "eye-of-the-tiger" sign. Molecular analysis of the PANK2 gene revealed a missense mutation in exon 5 (N501I). Our 2 cases demonstrate that the observation of a normal globus pallidus in the early stage of the disease does not exclude the diagnosis of classic PKAN.