Introduction. Spinal muscular atrophy type 1 is an autosomal recessive neuromuscular disorder characterized by degeneration of the anterior horn cells in the spinal cord, leading to symmetric muscle weakness and atrophy. 95% of affected children die before 2 years of age. The annual incidence in the world has been estimated at around 1/11 000. The errors (mutations) in the SMN1 gene prevalence vary from 1: 38 to 1: 70 in the population. The disorder is primarily caused by the homozygous deletions of the gene (5q12.2-q13.3). The SMN gene mutation is primarily caused by a homozygous deletion in exons 7 or 8.
Case presentations. 2 clinical cases of children with the Werdnig-Hoffmann disorder will be presented, and a literature review of this pathology. Two cases of spinal muscular atrophy diagnosed in Chernivtsi region, Ukraine, are presented. In both children, a molecular genetic analysis found the homozygous deletions of SMN1 gene in exons 7 and 8. Most affected children die within 2.3- 1.3 years of age. These two cases ended lethally due to subinfection.
Material was collected in accordance with ethical standards of work person under Helsinki Declaration (World Medical Association Declaration of Helsinki, Ethical Principles for Medical Research Involving Human Subjects). Genealogical analysis of families, biochemical analysis of blood, ENMG were carried out. The molecular genetic method was used: DNA was extracted and the deletions of 7 and 8 exons of the telomeric SMN gene were tested by PCR method. The disorder usually manifests in young children, if mother has a history indicating a weak fetal movement during pregnancy. Hypotension and hypotrophy of muscles, absence of tendon reflexes on lower extremities, fibrillation of the muscles of the tongue and fingers are observed in the neonatal period. Children with this pathology can poise their heads, but never turn over and do not sit. They are characterized by a „frog“ position: the limbs are laid in the shoulder and femoral joints and bent in elbow and knee joints. Chest distortions are pathognomonic. The main cause of death is respiratory distress associated with intercurrent respiratory disorders.
Conclusion. Based on the literature data and our experience of monitoring children with SMA type I, the disorder has a malignant rapidly progressing course.
Keywords: Werdnig-Hoffmann disease, spinal muscular atrophy, SMN1 and SMN2 gene, children.
Abbreviations. PCR – polymerase chain reacti on; ENMG – electroneuromyography; SMA – Spinal Muscular Atrophy.
Address for correspondence:
Mariana Alexandrovna RYZNYCHUK
Nezavisimosti Ave., 95/27
Chernivtsi, Ukraine, 58005
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