ABSTRACT
Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by progressive anterior horn cell degeneration leading to motor weakness, muscular atrophy and denervation. Recently, the genes responsible for proximal muscular atrophy have been identified and named as survivor motor neuron (SMN) and neuronal apoptosis inhibitory protein genes. The clinical symptoms, courses and evaluation findings of proximal SMA type III are similar to those of distal SMA and proximal muscle myopathies such as limb gir-dle muscular dystrophy and fascioscapulohumeral muscular dystrophy. It cannot be diagnosed with muscle biopsy and electromyographic findings exclusively. In our case, the patient showed similar clinical manifestations of distal SMA. So we couldn't diagnose this case as SMA type III until we detected SMN 1 gene deletion. This case could be a good model for diagnostic approach to SMA type III and differential diagnosis to similar diseases.
Subject(s)
Humans , Anterior Horn Cells , Atrophy , Biopsy , Denervation , Diagnosis, Differential , Extremities , Gene Deletion , Motor Neuron Disease , Motor Neurons , Muscle Weakness , Muscular Atrophy , Muscular Atrophy, Spinal , Muscular Diseases , Muscular Dystrophies , Neuronal Apoptosis-Inhibitory Protein , SurvivorsABSTRACT
We present two cases of the patients with spinal muscular atrophy(SMA) confirmed by molecular genetic studies. The first one is 1-year-old female child with SMA type II(Dubowitz disease) who visited pediatric outpatient for developmental delay. She presented lower extremity hypotonia which progress to upper extremities and inability to sit alone. Spinal cord MRI showed normal findings but the needle electromyography suggested the possibility of myopathy. Following muscle biopsy findings were consistent with spinal muscular atrophy and PCR-SSCP(polymerase chain reaction-single strand conformation polymorphism) analysis showed homozygous deletion of telomeric SMN(survivor motor neuron) exon 7. The second is a 19-year-old female with SMA type III(Kugelberg-Welander disease) who visited neurologic outpatient for limbs weakness. She presented slowly progressive gait disturbance without muscle atrophy. The significantly decreased motor power of proximal limbs was observed. And findings of electromyography and muscle biopsy were consistent with spinal muscular atrophy. PCR-SSCP analysis revealed homozyous deletion of exon 7 of telomeric SMN and deletion of exon 8 of centromeric SMN gene. PCR analysis for NAIP(neuronal apoptosis inhibitory protein) exon 5 and 13 revealed no deletion in both cases. Molecular genetic analysis for SMN gene will be very useful for rapid diagnosis of spinal muscular atrophy.