[Pilar dysplasia: an early marker of giant axonal neuropathy]

Giant axonal neuropathy is an autosomal recessive condition characterized by progressive degeneration of the central and peripheral nervous system. Sensoromotor neuropathy develops around 3 years of age. Children have particular faces with curly hair. Characteristic pilar anomalies occur early and have diagnostic value. CARE REPORT: An Algerian boy born to consanguineous parents (first cousins) had language retardation and gait disorders developed around 3 years of age. At 9 years, the child was in a cachetic state with valgus feet, amyotrophy and diminished muscle force predominating distally, ataxia, areflexia, sensoromotor neuropathy and nystagmus. Skin tropism was altered with pale, thin and dry skin, cold, cyanotic limbs and thick curly hair. Electrophysiology explorations showed signs of chronic sensoromotor polyneuropathy with axonal predominance. Brain and spinal MRI revealed cerebellar atropy and signs of leukodystrophy. The spinal tap was normal. A neuromuscular biopsy confirmed the diagnosis of giant axonal neuropathy. At examination the hair was thick with reduced refrangibility and a pseudo-pili torti aspect.

Giant axonal neurpathy is characterized by anomalous organization of the cytoskeleton of intermediary filaments in different types of cells. Hair anomalies occur early, before onset of neurological signs. At gross examination the hair is thick and curly, sometimes crimped and pale. Examination of the pilar shaft shows trichorrhexis nodosa, scalloped fringes and lack of internal structure. On the molecular level, there is a reduction in the number of bisulfur bridges which could be the cause of defective keratin filament alignement. Pathogenicaly, the pilar anomalies are considered as a direct manifestation of defective keratin organization characteristic of the disease.