Atypical Presentation of the GLUT-1 Deficiency Syndrome with Cataract and Normal Glucose Concentration in Cerebrospinal Fluid

Background: The SLC2A1 gene on chromosome 1 encodes a glucose transporter in the blood-brain barrier. A defect of this gene is responsible for the glucose transporter 1 (GLUT-1) deficiency syndrome, a metabolic disease which leads to an undersupply of glucose for the brain. Main symptoms are infantile-onset seizures refractory to anticonvulsant medications, an acquired microcephaly, and developmental delay and movement disorders. Other than the mentioned diseases, there is a rare form of hereditary stomatocytosis, called stomatin-deficient cryohydrocytosis, caused by a mutation in the same gene as the mutation of the GLUT-1 deficiency syndrome. The patients show anemia, a cataract, as well as neurological symptoms such as epilepsy, developmental delay, and movement disorders. In our case report, we present a new mutation of the SLC2A1 gene which includes symptoms of both clinical pictures in the phenotypical spectrum.

Case: We report on a patient with a detected mutation in the SLC2A1 gene and clinical symptoms of the GLUT-1 deficiency syndrome. Among the classical symptoms such as infantile-onset epilepsy resistance to therapy, developmental delay, and movement disorders, there are also atypical symptoms such as a cataract and splenomegaly. Other untypical diagnostic findings are normal glucose concentration in the cerebrospinal fluid and the absence of secondary microcephaly.

Conclusion: The detected mutation extended the phenotypical spectrum of the known mutations in the SLC2A1 gene. The differential diagnosis of infantile-onset seizures refractory to anticonvulsant medications in combination with cataract should contain the GLUT-1 deficiency syndrome. In addition, normal concentration of glucose in the cerebrospinal fluid in combination with earlier named symptoms should not be a criterion of exclusion for the GLUT-1 deficiency syndrome in the potential diagnosis. Furthermore, in a combination with anemia, cataract and neurological symptoms, a mutation in the SLC2A1 gene should be considered. Particularly, in regard to potential therapy with ketogenic diet, it is to prove whether this form of treatment could influence the neurological symptoms of patients with mutation in the SLC2A1 gene and an atypical presentation of the GLUT-1 deficiency syndrome.