AP4 deficiency: A novel form of neurodegeneration with brain iron accumulation?

Objective: To describe the clinico-radiological phenotype of 3 patients harboring a homozygous novel AP4M1 pathogenic mutation. Methods: The 3 patients from an inbred family who exhibited early-onset developmental delay, tetra-paresis, juvenile motor function deterioration, and intellectual deficiency were investigated by magnetic brain imaging using T1-weighted, T2-weighted, T2∗-weighted, fluid-attenuated inversion recovery, susceptibility weighted imaging (SWI) sequences. Whole-exome sequencing was performed on the 3 patients. Results: In the 3 patients, brain imaging identified the same pattern of bilateral SWI hyposignal of the globus pallidus, concordant with iron accumulation. A novel homozygous nonsense mutation was identified in AP4M1, segregating with the disease and leading to truncation of half of the adap domain of the protein. Conclusions: Our results suggest that AP4M1 represents a new candidate gene that should be considered in the neurodegeneration with brain iron accumulation (NBIA) spectrum of disorders and highlight the intersections between hereditary spastic paraplegia and NBIA clinical presentations. Copyright © 2018 The Author(s).