Transient cytoplasmic bodies in muscle of three infants with Werdnig-Hoffmann disease

[Diagnostic difficulties in spinal muscular atrophy]

OBJECTIVE

To describe the clinical findings of patients with spinal muscular atrophy (SMA) with survival motor neuron (SMN) gene deletion.

METHOD

Descriptive study of SMA cases confirmed with the deletion of the SMN gene. Frequency determination of positive clinical and laboratory revised diagnostic criteria.

RESULTS

All of the 22 included patients had symmetrical muscle weakness, which was diffuse in those with onset of symptoms up to 6 months of age (75 %), and either proximal or predominant in lower limbs in the remaining group (67 %). Fasciculations and atrophy were both frequent findings (82 %). Laboratory tests findings were variable, with a positivity of 57 % for electrophysiology and of 58 % for muscle biopsy.

CONCLUSION

The presence of a deletion in the SMN gene can help to confirm this diagnosis in unclear presentations.

Axonal neuropathy and predominance of type II myofibers in infantile spinal muscular atrophy

Two affected siblings with infantile spinal muscular atrophy (SMA I) presented with generalized muscular hypotonia, which progressed to early death. Quadriceps muscle biopsy did not show the typical neurogenic pattern of spinal muscular atrophy. The histochemical fiber type determination revealed a predominance of type II fibers without type I hypertrophy, an unprecedented finding in spinal muscular atrophy. Sural nerve biopsy exhibited findings typical for axonal neuropathy. In one patient, electrical stimulation of peripheral nerves showed an inexcitability of motor and sensory nerves. Genetic studies revealed homozygous deletions of the telomeric survival motor neuron (SMN) gene and the neuronal apoptosis inhibitory protein (NAIP) gene in the affected children. This is the second case report of molecular genetically proven spinal muscular atrophy associated with axonal neuropathy. We conclude atypical findings on muscle biopsy and evidence of axonal neuropathy are compatible with the diagnosis of infantile spinal muscular atrophy.