Spinal Muscular Atrophy Lower Extremity Predominant 2b Prenatal Onset Autosomal Dominant C4749003
A severe genetic neuromuscular disorder causing progressive muscle weakness in the legs from before birth. Inherits autosomal dominantly and affects motor neurons, requiring multidisciplinary supportive care.
Key facts at a glance
- ICD-10
- G40.909
- ICD-11
- 8A00.0
- Body system
- neurologic
- Severity
- severe
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Warning signs - seek immediate care
Respiratory insufficiency
Generalized symptoms
(neurologic)Significant symptoms that substantially affect daily functioning.
Frequency: Common at all stages
Progressive muscle weakness
(neurologic)Motor developmental delay
(neurologic)Joint contractures
(neurologic)Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Disease-Modifying Therapy
Treatment with SMA-specific disease-modifying agents that target the underlying genetic cause. These therapies aim to increase functional SMN protein levels and may slow disease progression.
Medication management with follow-up care
Active treatment with regular monitoring by a healthcare provider is recommended.
Musculoskeletal Maintenance Program
Comprehensive physical therapy including passive range of motion, gentle stretching, and positioning to prevent contractures. Aquatic therapy provides low-impact exercise and resistance training.
Additional treatment options
Orthopedic Intervention
Surgical procedures to address severe contractures, scoliosis, or hip subluxation including tendon releases, spinal fusion, and joint stabilization. Timing requires careful multidisciplinary planning.
surgicalRespiratory Function Monitoring
Regular pulmonary function testing and sleep studies to monitor for respiratory muscle weakness and nocturnal hypoventilation. Early intervention with cough assist and non-invasive ventilation may be needed.
monitoringNutritional Support and Swallowing Therapy
Nutritional assessment and management including caloric optimization, texture-modified diets if needed, and supplementation. Feeding therapy addresses swallowing difficulties and prevents aspiration.
dietaryWhen to seek medical help
Recognize when you need immediate medical attention.
See a doctor within 24 hours
Moderate to severe symptoms that may indicate worsening of this condition. Prompt medical evaluation is recommended.
Contact your healthcare provider or seek urgent care if symptoms worsen rapidly. Go to the emergency department for life-threatening symptoms.
Frequently asked questions
Common questions about this topic.
What is Spinal Muscular Atrophy Lower Extremity Predominant 2b Prenatal Onset Autosomal Dominant C4749003?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Mercuri E, Finkel RS, Muntoni F, et al. Diagnosis and management of spinal muscular atrophy: part 1. Recommendations of the SPMA Care and Treatment Advisory Board. Neuromuscul Disord. 2021.
Wang CH, Kolb SJ, Prior TW. Spinal muscular atrophy: mechanisms and therapeutic targets. Neurotherapeutics. 2022.
Finkel RS, Mercuri E, Darras BT, et al. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2020.
Luo M, Song B, Zhu J. Genotype-phenotype correlation in spinal muscular atrophy: a meta-analysis. J Neurol. 2023.
Medication Comparisons
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View Medication ComparisonsThis information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy