X-linked bulbo-spinal neuronopathy of late onset

Ocular myasthenia gravis associated with x-linked recessive spinal and bulbar muscular atrophy

We describe a 34-year-old patient who was admitted with episodic diplopia, ptosis, and swallowing difficulties of 6 months duration. He also had some muscle cramps aggravated by exercise since the age of 20. Bilateral ptosis of the eyelids, normal gaze, rare fasciculations of the tongue, easy fatigability of ocular and bilateral proximal limb muscles, atrophy of the testes, and gynecomastia were found on neurologic examination. Repetitive nerve stimulation studies and jitter measurement disclosed the defect of neuromuscular junction transmission. Acetylcholine receptor binding antibody was not detected. Acetylcholine esterase inhibitors relieved these episodic symptoms. A genetic study that showed an expansion of cytosine-adenine-guanine (CAG) repeat in the first exon of the androgen receptor (AR) confirmed the diagnosis of X-linked recessive spinal and bulbar muscular atrophy (X-SBMA). Thus, this case shows a rare association of ocular myasthenia gravis with X-SBMA.

Clinical aspects of CAG repeat diseases

Seven neurodegenerative disorders are known to be caused by unstable expansions of the trinucleotide CAG within human genes, and more will be discovered in the coming years. These disorders share some clinical similarities, as well as some differences, which are summarized here. These diseases have unusual clinical genetic properties related to the dynamic nature of CAG repeat expansions, including instability of the repeat expansion in meiosis, particularly male meiosis; a strong correlation between onset age and size of the repeat expansion; anticipation (earlier disease onset in succeeding generations); new mutations arising from unstable, mutable alleles with a high-normal CAG repeat number; and reduced penetrance for alleles in the low-affected range. Much more remains to be learned about the molecular biology and clinical pathophysiology of this new class of genetic diseases.

X-linked recessive bulbospinal neuronopathy (Kennedy's syndrome): a neurophysiological study

We examined 8 men with X-linked recessive bulbospinal neuronopathy. Quantitative electromyography showed large amplitude motor unit action potentials of prolonged duration and increased polyphasia. There was a pronounced loss of motor units in all but one muscle at maximal volition even in muscles with normal or only mildly decreased force. Denervation activity was present in 53% sampled limb muscles, and fasciculation was recorded in 33% of limb muscles. Nerve conduction studies showed small amplitude sensory action potentials in 6 out of 8 patients. The motor and sensory conduction velocity was normal or borderline slow. The electrophysiologic findings were consistent with chronic partial denervation (motor axonopathy) combined with large fibre sensory axonopathy.

X-linked bulbospinal muscular atrophy (Kennedy's syndrome): a report of three cases

Two cases of X-linked bulbo-spinal muscular atrophy and one sporadic case with the same clinical features are presented. All three cases were extensively studied by electrophysiological methods. One of the patients showed some transient weakness, which was partly improved by pyridostigmin. In this patient the Decrement test and jitter revealed a mild degree of motor-end plate dysfunction. Clinical and electrophysiological findings obtained from all three patients suggest that in Kennedy syndrome cell bodies of group IA muscle afferents are also affected selectively, with other peripheral afferents.

Clinical-anatomic study of a family with bulbo-spinal muscular atrophy in adults

Four cases are presented, with bulbo-spinal muscular atrophy characterised by adult onset and rapid evolution. They belong to a family in which the type of inheritance is probably dominant. Two cases were studied histologically. The most striking feature was the disappearance of neurons in the lower motor nuclei of medulla and of the spinal anterior horns. An electron microscopic study was carried out in one case. Accumulation of neurofilaments was a general characteristic, in addition to the picture of different sized spheroids. The clinical-pathological relationship is discussed.