The Jokela type of spinal muscular atrophy (SMAJ) is an autosomal dominant lower motor neuron disorder characterized by adult-onset of muscle cramps and fasciculations affecting the proximal and distal muscles of the upper and lower limbs. The disorder ... The Jokela type of spinal muscular atrophy (SMAJ) is an autosomal dominant lower motor neuron disorder characterized by adult-onset of muscle cramps and fasciculations affecting the proximal and distal muscles of the upper and lower limbs. The disorder is slowly progressive, resulting in weakness and mild muscle atrophy later in life (summary by Jokela et al., 2011).
Jokela et al. (2011) reported 2 large unrelated Finnish families with late adult-onset spinal muscular atrophy. Twelve individuals were examined. Affected individuals developed painful muscle cramps associated with slowly progressive weakness and atrophy of the proximal and distal ... Jokela et al. (2011) reported 2 large unrelated Finnish families with late adult-onset spinal muscular atrophy. Twelve individuals were examined. Affected individuals developed painful muscle cramps associated with slowly progressive weakness and atrophy of the proximal and distal muscles of the upper and lower limbs. Fasciculations were almost always present, reflexes were absent, and EMG showed neurogenic changes. All retained the ability to walk independently, even after long disease duration. Five patients had pes cavus, 1 had pes planus, 3 had hammertoes, and 2 had calf hypertrophy. Five had reduced vibration sense in the distal part of the feet, and 5 had intention tremor. Serum creatine kinase was increased in most patients. Muscle imaging showed diffuse fatty degenerative changes in the posterior lower leg muscles. Muscle biopsy showed fiber-type grouping, consistent with denervation. Biopsy of 1 patient showed myopathic changes. None had bulbar signs, and extensor plantar responses were not present. The phenotype was consistent with a lower motor neuronopathy.