Viliuisk encephalomyelitis--review of the spectrum of pathological changes

Viliuisk encephalomyelitis (VE) is an unique neurological disease occurring in the Iakut (Sakha) people of Siberia. Evolution of the disease follows one of three broad clinical forms: subacute, slowly progressive or chronic. Death occurs within 3 to 6 months in subacute cases and within 6 years in the slowly progressive cases. Chronic cases lack a subacute phase but show a slowly progressive dementia associated with bradykinesia, dysarthria and spastic paraparesis that stabilizes late in the disease process. In subacute and slowly progressive cases, focal necrotizing encephalomyelitis is seen at necropsy. Chronic cases show multifocal areas of lysis with a gliotic margin, predominantly within grey matter, lacking associated chronic inflammatory changes seen in the other forms of the disease. Epidemiological studies are consistent with a disease of low-grade communicability, but laboratory studies have so far failed to reveal an infectious organism. The spectrum of neuropathological changes are reviewed in this examination of 11 cases. Although the aetiology of VE remains obscure, further studies are warranted since it may represent a novel disease process.

Unstable triplet repeat and phenotypic variability of spinocerebellar ataxia type 1

A Siberian kindred with spinocerebellar ataxia genetically linked to the SCA1 locus on chromosome 6p has been screened for the CAG triplet expansion within the coding region of the SCA1 gene. The kindred includes 1,484 individuals, 225 affected and 656 at risk, making this collection the largest spinocerebellar ataxia type 1 (SCA1) pedigree known. Each of the studied 78 SCA1 patients carried an expanded allele containing a stretch of 39 to 72 uninterrupted CAG repeats. Normal alleles had 25 to 37 trinucleotide repeats. Expanded alleles containing 40 to 55 repeats were found in 26 at-risk relatives. The number of CAG repeats in the mutated allele was inversely correlated with age at disease onset. Cerebellar deficiency was present in each patient and its severity was moderately affected by the number of CAG repeats. In contrast, the associated signs, dysphagia, diffuse skeletal muscle atrophy with fasciculations, and tongue atrophy were absent or mild in patients with low CAG repeat numbers, but severely complicated the course of illness in patients with a larger number of repeat units. One female mutation carrier was asymptomatic at age 66, more than 2 standard deviations beyond the average age of risk, suggesting incomplete penetrance. In 2 symptomatic individuals who had an expanded number of CAG repeats on both chromosomes, age at onset, rate of progression, and clinical manifestation corresponded to the size of the larger allele.

[Modern concepts of the metabolism and genetic polymorphism of collagen (a review)]

The data on structure, biosynthesis, post-synthetic modifications, extracellular development and degradation of collagen are briefly reviewed. Role of main enzymes, participating in collagen turnover, is discussed. Isoforms of the protein are considered in details. The importance of studies on collagen proteins is noted in connection with investigations on morphogenesis, cell differentiation, regeneration.