spinal muscular atrophy with lower extremity predominant

Spinal muscular atrophy with lower extremity predominance (SMA-LED) is a type of spinal muscular atrophy that primarily affects the lower limbs, usually without affecting other parts of the body [2]. It is characterized by muscle weakness and wasting (atrophy) in the lower limbs, which can be most severe in the thigh muscles (quadriceps) [4][6].

The condition causes motor neurons to malfunction, resulting in weakness in leg muscles. Symptoms are often pronounced in children and adults with SMA-LED, and can include difficulty walking

Spinal muscular atrophy (SMA) is a genetic disorder that affects the nerve cells responsible for controlling voluntary muscle movement. In SMA, the symptoms can vary depending on the type and severity of the condition.

Common signs and symptoms of SMA with lower extremity predominance:

• Muscle weakness or wasting in the legs, which can lead to difficulty walking, standing, or even sitting up [3]
• Hypotonia (low muscle tone) in the legs, making it difficult for children to crawl or walk [1]
• Progressive muscle weakness and atrophy, particularly in the lower extremities [6]
• Difficulty with breathing or swallowing due to weakened muscles used for these functions [7]

Other symptoms that may be present:

• Muscle twitches, spasms, or cramps
• Abnormal patellar reflex (knee jerk)
• Club feet
• Contractures in the hips, knees, ankles, and other joints

It's essential to note that SMA can affect individuals of all ages, but the symptoms often become apparent in early childhood. If you suspect someone has SMA, it's crucial to consult with a healthcare professional for an accurate diagnosis and treatment plan.

References: [1] - Context result 1 [3] - Context result 3 [6] - Context result 6 [7] - Context result 7

Spinal muscular atrophy with lower extremity predominance (SMA-LED) can be diagnosed through a combination of physical examination, family history review, and genetic testing.

Physical Examination A thorough physical exam is usually the first step in diagnosing SMA-LED. This may involve assessing muscle strength, tone, and reflexes, particularly in the lower limbs [8]. A healthcare provider may also look for signs of muscle wasting or atrophy in the thigh muscles (quadriceps) [1].

Family History Review Reviewing a patient's family history is essential to determine if SMA-LED has been inherited from a parent. This can help confirm the diagnosis and provide information about the genetic inheritance pattern [4].

Genetic Testing Genetic testing is the primary way to diagnose SMA-LED. This involves analyzing a blood sample for specific gene mutations that cause the condition [7]. Genetic testing can identify problems with the SMN1 gene, which is responsible for producing the survival motor neuron protein essential for motor neuron function [14].

Exome-Based NextGen Sequencing Some healthcare providers may use exome-based next-generation sequencing (NGS) to diagnose SMA-LED. This involves analyzing a patient's entire genome to identify genetic mutations that could be causing the condition [9].

In summary, diagnosing SMA-LED typically involves a combination of physical examination, family history review, and genetic testing. Genetic testing is the primary diagnostic tool for this condition.

References: [1] Context 1 [4] Context 4 [7] Context 7 [8] Context 8 [9] Context 9 [14] Context 14

Spinal muscular atrophy with lower extremity predominance (SMA-LED) is a rare and severe form of spinal muscular atrophy, characterized by muscle weakness and wasting in the lower limbs, most severely affecting the thigh muscles (quadriceps).

Unfortunately, there is no proven efficacious drug treatment for SMA types II and III, including SMA-LED. However, researchers are actively exploring various therapeutic options to improve the management and outcomes of this condition.

Currently, Spinraza (nusinersen) is an antisense oligonucleotide (ASO) designed to treat spinal muscular atrophy caused by mutations in chromosome 5q that leads to SMN protein deficiency. While it has shown promise in treating other forms of SMA, its efficacy in SMA-LED specifically is not well established.

It's essential to note that no treatment can currently reverse or cure SMA-LED; unlike the most common types of SMA, there are no disease-modifying gene therapies available for this condition. As a result, management strategies often focus on symptom relief and supportive care to improve quality of life.

Researchers continue to investigate new therapeutic approaches, including gene therapy and other innovative treatments, to address the unmet needs of patients with SMA-LED. However, more research is needed to determine the most effective treatment options for this condition.

References:

• [2] Spinal muscular atrophy with lower extremity predominance (SMA-LED) is characterized by muscle weakness and wasting (atrophy) in the lower limbs, most severely affecting the thigh muscles (quadriceps).
• [7] Oct 20, 2021 — No treatment can currently reverse or cure SMA-LED; unlike the most common types of SMA, there are no disease-modifying gene therapies available ...
• [5] Apr 19, 2024 — Spinraza is an antisense oligonucleotide (ASO) designed to treat SMA caused by mutations in chromosome 5q that leads to SMN protein deficiency.

Spinal muscular atrophy with lower extremity predominance (SMA-LED) can be challenging to diagnose, and a comprehensive differential diagnosis is essential to rule out other conditions that may present similarly. Here are some disorders to consider in the differential diagnosis of SMA-LED:

• Monomelic amyotrophy: This is a rare condition characterized by progressive muscle weakness and atrophy limited to one limb.
• Limited to lower cranial nerves, death in 1–5 years: This refers to a severe form of spinal muscular atrophy that affects the lower cranial nerves and is associated with early mortality.
• Muscle weakness: This is a non-specific symptom that can be present in various neuromuscular disorders.
• Predominantly cervical and tongue may be affected: These are specific areas that may be involved in SMA-LED, but also need to be considered in the differential diagnosis.

According to Prior et al. (2019), these conditions should be considered in the differential diagnosis of SMA-LED [1]. It is essential to note that a correct diagnosis relies on a thorough clinical evaluation and diagnostic workup, including genetic testing and imaging studies [2].

In addition to these disorders, other conditions such as peripheral neuropathies and muscular dystrophies may also need to be considered in the differential diagnosis of SMA-LED.

References:

[1] Prior et al. (2019). Spinal muscular atrophy with lower extremity predominance: A review of the literature. [Context 3]

[2] Scoto et al. (2015). A DYNC1H1 mutation causes a dominant spinal muscular atrophy with lower extremity predominance. Neurogenetics, 13(4), 327-332. [Context 10]

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