Genetic heterogeneity in giant axonal neuropathy: an Algerian family not linked to chromosome 16q24.1

Giant axonal neuropathy is a rare severe autosomal recessive childhood disorder affecting both the peripheral nerves and the central nervous system. Peripheral nerves characteristically show giant axonal swellings filled with neurofilaments. The giant axonal neuropathy gene was localised by homozygosity mapping to chromosome 16q24.1 and identified as encoding a novel, ubiquitously expressed cytoskeletal protein named gigaxonin. We describe a consanguineous Algerian family with three affected sibs aged 16, 14 and 12 years who present a mild demyelinating sensory motor neuropathy, hypoacousia and kyphoscoliosis which was moderate in the two elder patients, severe in the third one, with no sign of central nervous system involvement and normal cerebral magnetic resonance imaging. This clinical picture is different from the classical severe form, with kinky hairs and early onset of central nervous system involvement and from the less severe form, with protracted course and late involvement of central nervous system. Nerve biopsy showed a moderate loss of myelinated fibers and several giant axons with thin or absent myelin, filled with neurofilaments. This neuropathological aspect is similar to the previously described families linked to the gigaxonin gene. Genetic study in this family showed absence of linkage to chromosome 16q24.1, indicating for the first time, a genetic heterogeneity in giant axonal neuropathy. We propose to call this form of giant axonal neuropathy giant axonal neuropathy 2, and to use the name of giant axonal neuropathy 1 for the form linked to 16q24.1.