A gene for an autosomal recessive lower motor neuron disease with childhood onset maps to 1p36.

OBJECTIVE: To describe the clinical features of a novel variant of autosomal recessive lower motor neuron disease (LMND) with childhood onset and to map the disease-causing gene. METHODS: The authors performed a clinical study in a large consanguineous African family. After linkage exclusion to SMN1 and SOD1 loci, they performed a genome-wide linkage analysis to map the underlying genetic defect. RESULTS: This novel variant of LMND with childhood onset and autosomal recessive mode of inheritance is characterized by a progressive symmetric and generalized involvement of the musculature. Four of the five affected patients had muscle weakness since age 3, strongly worsening during childhood and leading to generalized tetraplegia in adulthood. Genetic analyses using homozygosity mapping strategy assigned this progressive generalized LMND locus to an interval of 3.9 cM (or 1.5 megabases) on chromosome 1p36, between loci D1S508 and D1S2633 (Z(max) = 3.79 at theta = 0.00 at locus D1S253). This region encloses 27 candidate genes. CONCLUSION: Genetic mapping of a novel rare phenotype of lower motor neuron disease opens the way toward the identification of a new gene involved in motor neuron degeneration, located in the 1p36 chromosomal region.

[Infantile spinal muscular atrophy]. / Amyotrophie spinale infantile.

The authors report 100 cases with prolonged spinal muscular atrophy (SMA) and survival beyond 4 years old. There were 46 boys and 54 girls. 23 of them had histories with an autosomal recessive form of inheritance. One case had a dominant form. The unity of cases described as Werdnig Hoffman disease [SMA I, SMA II (Childhood), ans SMA III (Kugelberg Welander)] is supported and our cases fell in three groups according to their ambulatory capabilities: never acquired, lost, or retained. 71 cases have never walked: the onset of symptoms was noted at an average age of 6.4 months +/- 3; the average age at the last examination was 16 years (4-39). Death occurred in 6 cases. Loss of walking occurred in 24 cases: the onset of symptoms was noted at an average age of 17.4 months +/- 14.2. 5 cases were still ambulatory: the onset of symptoms was noted at an average age of 2.4 years +/- 2.8. For these last 29 cases the average age at the last examination was 20 years (4-38); death occurred in two cases. The weakness was symmetrical and proximal. The period of worsening varied but, frequently, patients with a later onset of symptoms had a longer period of deterioration. Tongue fasciculations were present in all cases who never walked. Facial and masseter weakness occurred in 3 cases. Oesophagus dyskinesia and distension of the stomach due to brain stem lesions occurred in many cases. This brain stem damage was responsible of 2 sudden deaths (8-30 years). Premature puberty occurred in 14 cases.(ABSTRACT TRUNCATED AT 250 WORDS)