Atypical neuroaxonal dystrophy in childhood related to PLA2G6: a French cohort

Atypical neuroaxonal dystrophy (ANAD) is a rare form of neurodegeneration linked to the PLA2G6 gene. Unlike classical infantile neuroaxonal dystrophy (INAD), it occurs later in childhood and seems less progressive. It appears phenotypically different from juvenile form of Parkinson disease linked to PLA2G6 (PARK14). A genotype-phenotype correlation has been suggested. We describe a large genetically confirmed cohort of pediatric patients with ANAD, describe their clinical symptomatology, brain imaging, other complementary explorations, symptomatic medication and compare to patients reported in the literature. Fourteen patients were identified with early childhood onset and slowly progressive cerebello-spastic syndrome with variable dystonia and parkinsonism. Complementary investigations were inconsistently abnormal compared to INAD, with variable iron deposits on brain imaging, infrequent rapid rhythms on EEG and absence of neuronal spheroids on skin biopsy leading to diagnosis difficulties in absence of large molecular analysis. Nine of the seventeen reported variants were novel variants and a relative genotype-phenotype correlation was confirmed. This study reports a large cohort of ANAD, providing new insights into this paediatric phenotype; which is less frequently described in the literature compared to INAD or PARK14.