Juvenile amyotrophic lateral sclerosis

Chapter 15 Juvenile amyotrophic lateral sclerosis

Several forms of genetically defined juvenile amy-otrophic lateral sclerosis (ALS) have now been charac-terized and discussion of these conditions will form the basis for this chapter. ALS2 is an autosomal recessive form of ALS with a juvenile onset and very slow progression that mapped to chromosome 2q33. Nine different mutations have been identified in the ALS2 gene that result in premature stop codons, suggesting a loss of function in the gene product, alsin. The alsin protein is thought to function as a guanine-nucleotide exchange factor for GTPases and may play a role in vesicle transport or membrane trafficking processes. ALS4 is an autosomal dominant form of juvenile onset ALS associated with slow progression, severe muscle weakness and pyramidal signs, in the absence of bulbar and sensory abnormalities. Mutations in the SETX gene cause ALS4, and the SETX gene product senataxin may have DNA and RNA helicase activity and play a role in the regulation of RNA and/or DNA in the cell. A third form of juvenile-onset ALS (ALS5) is associated with slowly progressing lower motor neuron signs (weak-ness and atrophy) initially of the hands and feet, with eventual bulbar involvement. Progressive upper motor neuron disease becomes more obvious with time. ALS5 has been linked to a 6 cM region of chromosome 15q15.1-q21.1, but the causative gene mutation for ALS5 has yet to be identified. The high degree of clin-ical and genetic heterogeneity in the various forms of juvenile ALS can make differential diagnosis difficult, other genetic disorders that must be considered include: spinal muscular atrophy, hereditary spastic paraplegia, SBMA, GM2 gangliosidosis and the hereditary motor neuronopathies/motor forms of Charcot-Marie-Tooth disease. Acquired disorders that must also be consid-ered include heavy metal intoxications (especially lead), multifocal motor neuropathy, paraneoplastic syndromes, vitamin deficiencies (B12) and infections (HTLV-II, HIV and poliomyelitis).

Motor neuron diseases in the university hospital of Fortaleza (Northeastern Brazil): a clinico-demographic analysis of 87 cases

In this retrospective (1980-1998) study, we have analyzed clinico-demographically, from the records of the University Hospital of Fortaleza (Brazil), a group of 87 patients showing signs and symptoms of motor neuron diseases (MNDs). Their diagnosis was determined clinically and laboratorially. The WFN criteria were used for amyotrophic lateral sclerosis (ALS) diagnosis. The clinico-demographic analysis of the 87 cases of MNDs showed that 4 were diagnosed as spinal muscular atrophy (SMA), 5 cases as ALS subsets: 2 as progressive bulbar paralysis (PBP), 2 as progressive muscular atrophy (PMA) and 1 as monomelic amyotrophy (MA), and 78 cases of ALS. The latter comprised 51 males and 27 females, with a mean age of 42.02 years. They were sub-divided into 4 groups according to age: from 15 to 29 years (n= 17), 30 to 39 years (n= 18), 40 to 69 years (n= 39) and 70 to 78 years (n= 4). From the 78 ALS patients, 76 were of the classic sporadic form whilst only 2 were of the familial form. The analysis of the 87 patients with MNDs from the University Hospital of Fortaleza showed a predominance of ALS patients, with a high number of cases of juvenile and early onset adult sporadic ALS.

Morphometric study of the sensory nerve in classical (or Charcot disease) and juvenile amyotrophic lateral sclerosis

Analysis of the superficial peroneal nerve sampled in 9 cases of classical amyotrophic lateral sclerosis (classical ALS, Charcot disease) and compared with 8 age-matched controls showed a very significant reduction of all myelinated fibres (P less than 0.001), affecting small-diameter (P less than 0.01) and large-diameter (P less than 0.02) fibres. Moreover, the small-diameter unmyelinated fibres were very significantly reduced (P less than 0.001) and the large-diameter fibres were highly increased (P less than 0.01). These results suggest a phenomenon of chronic axonal degeneration. Analysis of the same nerve in 7 patients suffering from juvenile ALS and compared with 4 age-matched controls showed a significant reduction (P less than 0.05) of myelinated fibres. The small-diameter and overall unmyelinated fibres were not significantly reduced while the large-diameter fibres, were significantly increased (P less than 0.01). The same analysis of 4 patients presenting an early-onset ALS compared with 3 controls showed lesions of a severity half-way between that of the classical and the juvenile form. Our study showed that the lesions of the sensory nerve are of the same type in classical ALS and in juvenile ALS, but of differing severity. The nosologic place of juvenile ALS compared with classical ALS and with heredodegenerative diseases of the nervous system is discussed.

Phenotypic and genotypic heterogeneity of dominantly inherited amyotrophic lateral sclerosis

Twenty-seven cases of hereditary amyotrophic lateral sclerosis (ALS), belonging to 8 families, are reported. The analysis of the pedigrees suggests an autosomal dominant transmission, apparently with incomplete penetration. The mean age at onset of symptoms was 50.3 (SD 12.4) years. The mean duration of the disease was 31.2 (SD 20.4) months, ranging from 9 to 86. The median survival time was 24 months. The degree of variation of some quantitative characters, both within and among families, was statistically analyzed. The results support the hypothesis of a phenotypic and genetic heterogeneity of autosomal dominant transmitted ALS.

An unusual case of lower motor neuron disease

An 11-year-old boy developed a rapidly progressive asymmetrical flaccid tetraparesis that ended fatally within 1 year. The classification of this unusual case is discussed.