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Rapidly progressive spinal muscular atrophy in an ambulatory 2-year-old male
Jaime Lin1, Ronaldo J M da Silva, Eugênio Grillo
1Department of Pediatrics, Hospital Universitário, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Santa Catarina, Brazil.
Insights
This case study highlights a child with spinal muscular atrophy (SMA) who rapidly lost ambulation within 18 months of symptom onset. Early SMN1 gene testing is crucial for diagnosing rapidly progressing SMA and avoiding unnecessary procedures.
Area of Science:
- Neurology
- Genetics
- Pediatrics
Background:
- Spinal muscular atrophy (SMA) is a genetic disorder characterized by progressive muscle weakness.
- Early diagnosis and understanding disease progression are vital for patient management and family counseling.
Observation:
- A 2-year 9-month-old male presented with gait disturbances and proximal lower limb weakness.
- The patient experienced frequent falls starting at 18 months, losing independent gait by age 3.
- Neurologic examination revealed decreased reflexes and generalized hypotonia.
Findings:
- Genetic analysis confirmed homozygous deletion in SMN1 gene exons 7 and 8, diagnosing SMA type III.
- The patient exhibited rapid motor deterioration, losing ambulation within 18 months of symptom onset.
- This case demonstrates that late symptom onset in SMA does not preclude rapid progression.
Implications:
- Rapidly progressive motor deterioration in SMA necessitates prompt SMN1 gene testing.
- Early diagnosis can prevent invasive procedures like lumbar puncture or EMG.
- Understanding disease trajectory is crucial for accurate prognostication and family discussions.
Abstract:
A 2-year 9-month-old male was referred for gait disturbances. Main complaints were abnormal gait with frequent falls observed as soon as he began to walk unaided, at 18 months of age. The first neurologic examination revealed symmetric and proximal weakness in the lower limbs with difficulty running and walking upstairs. Deep tendon reflexes were decreased, and generalized hypotonia was observed. Three months later, at 3 years of age, he had lost independent gait, and 1 month later he could not stand unaided. DNA analysis revealed homozygous deletion in exons 7 and 8 of SMN1 gene, confirming the diagnosis of spinal muscular atrophy. According to the current classification, this patient would be classified as spinal muscular atrophy type III. The distinctive feature of this case was the short time elapsed (18 months) between onset of spinal muscular atrophy and the age at which he lost ambulation. This patient reinforces the notion that late onset of symptoms in spinal muscular atrophy and acquisition of independent gait do not exclude a rapidly progressive motor deterioration, which is important when talking with families about outcome. In those rapidly progressive cases, when promptly available, testing for SMN1 gene will prevent unnecessary, invasive, or uncomfortable procedures such as lumbar puncture, electromyography, or spinal cord magnetic resonance imaging.
