Summary about Disease
Kugelberg-Welander disease (KWD), also known as spinal muscular atrophy type III or IV, is a genetic neuromuscular disorder characterized by progressive muscle weakness and atrophy. It is a milder form of spinal muscular atrophy (SMA) compared to types I and II. The severity and age of onset vary significantly, even within the same type.
Symptoms
Symptoms of KWD typically appear after infancy, often in childhood or adolescence, but can also manifest in adulthood. Common symptoms include:
Muscle weakness, particularly in the proximal muscles (muscles closer to the trunk), such as the hips and thighs.
Difficulty walking, running, or climbing stairs.
Fatigue.
Tremors or fasciculations (muscle twitching).
Muscle cramps.
Scoliosis (curvature of the spine) may develop.
Respiratory difficulties can occur in some cases, but are less common than in more severe forms of SMA.
Causes
KWD is caused by a mutation in the SMN1 (survival motor neuron 1) gene located on chromosome 5. This gene produces a protein essential for the survival of motor neurons, which control muscle movement. Most affected individuals have a deletion or mutation of the *SMN1* gene on both chromosomes. A backup gene, *SMN2*, can also produce the SMN protein, but in insufficient amounts. The number of copies of the *SMN2* gene influences the severity of the disease. More copies of *SMN2* generally result in a milder phenotype. KWD is inherited in an autosomal recessive pattern, meaning both parents must carry a copy of the mutated gene for their child to be affected.
Medicine Used
Several medications are used to treat SMA, including KWD. These medications aim to either increase the amount of SMN protein produced or protect the motor neurons:
Nusinersen (Spinraza): An antisense oligonucleotide drug that modifies SMN2 splicing to produce more functional SMN protein. It is administered intrathecally (injection into the spinal fluid).
Risdiplam (Evrysdi): An oral SMN2 splicing modifier. It also works by increasing the amount of functional SMN protein.
Onasemnogene abeparvovec-xioi (Zolgensma): A gene therapy that delivers a functional copy of the SMN1 gene. It is administered as a one-time intravenous infusion.
Symptomatic treatments: Physical therapy, occupational therapy, and supportive care are essential for managing symptoms and maintaining function.
Is Communicable
Kugelberg-Welander disease is NOT communicable. It is a genetic disorder, meaning it is caused by a gene mutation and cannot be spread from person to person.
Precautions
Precautions for individuals with KWD and their families include:
Regular medical follow-up: To monitor disease progression and adjust treatment as needed.
Physical and occupational therapy: To maintain muscle strength and mobility.
Respiratory support: If breathing difficulties develop.
Genetic counseling: For families planning to have children, to understand the risk of recurrence.
Vaccinations: Maintaining recommended vaccinations to prevent infections.
Avoidance of prolonged immobilization: Promotes maintaining muscle function.
How long does an outbreak last?
Kugelberg-Welander disease is not an outbreak. As KWD is a genetic condition, there is no "outbreak" period. It is a chronic, progressive condition that can persist throughout a person's life.
How is it diagnosed?
Diagnosis of KWD typically involves:
Clinical evaluation: Assessment of muscle weakness, reflexes, and other neurological signs.
Genetic testing: To identify mutations in the SMN1 gene. This is the definitive diagnostic test.
Electromyography (EMG): To assess the electrical activity of muscles and nerves.
Muscle biopsy: In some cases, a muscle biopsy may be performed to examine muscle tissue.
Creatine kinase (CK) levels: Blood tests may show elevated CK levels, indicating muscle damage.
Timeline of Symptoms
The timeline of KWD symptoms can vary, but generally follows this pattern:
Onset: Symptoms typically begin after infancy, often in childhood or adolescence (sometimes adulthood).
Progression: Muscle weakness progresses slowly over time. The rate of progression varies.
Plateaus: Periods of stability may occur, where the disease does not progress significantly.
Late stages: In later stages, individuals may experience more significant mobility limitations and may require assistance with daily activities.
Important Considerations
Variability: KWD exhibits significant variability in its presentation and progression.
Early diagnosis: Early diagnosis and treatment are crucial to optimize outcomes.
Multidisciplinary care: Management requires a multidisciplinary approach involving neurologists, pulmonologists, physical therapists, occupational therapists, and other specialists.
Family support: Emotional and practical support for individuals with KWD and their families is essential.
Research: Ongoing research is focused on developing new and improved treatments for SMA, including KWD.