Hereditary neuropathy with liability to pressure palsies associated with central nervous system myelin lesions

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder most commonly caused by a 1.5-Mb deletion in chromosome 17p11.2 which contains the peripheral myelin protein-22 (PMP22) gene. Mutations resulting in functional loss of one PMP22 gene copy are less frequent. We present a 51-year-old patient with a l.5-Mb deletion in chromosome 17p11.2 who exhibited signs of peripheral as well as central nervous system lesions. He gave a history of recurrent episodes of limb numbness and weakness with spontaneous but incomplete recovery since age 20. His father and two brothers had similar symptoms. Neurological examination revealed signs of multiple mononeuropathy associated with frontal lobe, corticospinal tract and cerebellar dysfunction, as well as signs of initial cognitive impairment. Electrophysiological investigations showed a demyelinating peripheral nerve disease with multiple conduction blocks and conduction disturbances in both optic nerves. Magnetic resonance imaging of the brain revealed multiple subcortical and periventricular foci of myelin lesions. The association of central and peripheral nervous system lesions in this patient indicates a possible role of PMP22 not only in peripheral but also in central nervous system myelin structure.

[Comparison of the number of CAG repeats in the gene for androgen receptors in a control Yugoslav population and in patients with schizophrenia]

INTRODUCTION

Dynamic mutations were recently discovered causing hereditary non polyposis colon cancer. Soon almost 15 hereditary neurological diseases were described caused by the expansion of trinucleotide repeats in target genes. These mutations are unstable: the number of trinucleotide repeats is increasing from generation to generation. These mutations do not obey Mendelian low. There is a positive correlation between the number of repeats and the severity of clinical symptoms, as well as with the age of onset. This fact explains the genetical basis of anticipation. Since schizophrenia is showing non-Mendelian way of inheritance and anticipation, it is believed that it might be caused by trinucleotide repeats in some gene(s). We analysed the number of CAG triplets in the gene for androgen receptor (AR) where expansions are causing spinal and bulbar muscular atrophy in healthy and schizophrenic subjects. The aim of this study was to see if the androgen receptor gene in schizophrenic patients shows instability in the number of trinucleotide repeats.

PATIENTS AND METHODS

In healthy Yugoslav population we analysed 85 X chromosomes from 52 non-related individuals (33 females and 19 males) from healthy Yugoslav population and 84 X chromosomes (41 females and 2 males) from patients with schizophrenia. DNA was isolated from peripheral blood leukocytes and used for further PCR amplification of the segment of AR gene containing CAG repeats. The exact number of these repeats was determined by electrophoresis on a 5% denaturing polyacrilamide gel stained by silver.

RESULTS

In healthy Yugoslav population we detected 16 different AR alleles in which the number of CAG triplets was from 14 to 29. The most common alleles were with 23 repeats (14.1%) and with 22 repeats (12.9%). The average number of CAG triplets per allele was 20.91. In patients with schizophrenia we detected 13 AR different alleles. The number of triplets was from 17 to 30. The most common allele was with 22 repeats (25%). The average number of CAG triplets per allele was 22.1.