Hereditary peripheral neuropathies present a group of clinically and genetically heterogeneous entities. All known forms, including the various forms of Charcot-Marie-Tooth disease (CMT) are characterized as Mendelian traits and over 45 genes have been identified thus far. The mutational mechanism of the most common CMT type, CMT1A, is a 1.5 Mb chromosomal duplication at 17p12 that contains the gene PMP22. Deletion of PMP22 gene is associated with a different peripheral neuropathy, hereditary neuropathy with liability to pressure palsies (HNPP).

We report a case of nine years old boy seen in our out-patient department with CMT-1A whose microarray analysis revealed triplication in the region of PMP22 gene on the short arm of one chromosome 17. He presented with history of delayed walking at 4 years of age on the background of being floppy during infancy. Clinical examination revealed mild atrophy of calf muscles, mild hypotonia of lower limbs, pes cavus, absent deep tendon reflexes and a high stepping gait. Nerve conduction revealed severe demyelination neuropathy. In the family history his father, paternal aunt and paternal grandfather had history suggestive of lower motor neurone weakness but we did not have any further details.

Conclusion: Triplication of PMP22 region presenting with classical clinical and electrophysiological signs of CMT-1A has been described only once before to our knowledge. Whether it alters the long-term outcome of the condition is not known.