Logan Steele
Distal muscles are those farthest away from the hips and shoulders, including the hands, feet, forearms, and lower legs. Distal muscular dystrophy (DD) is a group of rare diseases that affect these muscles, causing weakness and wasting of muscles. The first symptom of DD is usually muscle weakness, followed by a visible decrease in muscle mass. DD is caused by a mutation in genes that code for proteins necessary for muscle function. The disease is passed down in a dominant manner, with a change in only one copy of the gene being enough to cause most forms of DD.
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What You'll Learn
- Distal muscular dystrophy (DD) is a group of rare diseases that affect distal muscles
- DD is caused by a mutation in genes that affect proteins necessary for muscle function
- DD affects the muscles in the lower arms, hands, lower legs, and feet
- The first symptom of DD is usually weakness in the distal muscles
- DD is inherited in an autosomal dominant pattern
Distal muscular dystrophy (DD) is a group of rare diseases that affect distal muscles
The onset of DD typically occurs between the ages of 40 and 60. However, it is important to note that the age of onset and the rate of progression can vary widely depending on the specific type of DD. For example, Finnish (tibial) distal myopathy usually appears after the age of 40, while Miyoshi distal myopathy shows up earlier, between the ages of 15 and 30. Some forms of DD, such as Nonaka distal myopathy, can affect people of all ages, with symptoms ranging from muscle weakness in adults to more severe muscle problems in children.
DD is caused by mutations in certain genes that affect the proteins necessary for muscle function. These genetic defects are usually passed down through families, and having a family history of DD puts an individual at a higher risk. Most forms of DD are dominant, meaning that a change in only one copy of the gene inherited from either parent is enough to cause the disease. However, some types of DD, such as Nonaka distal myopathy and Miyoshi muscular dystrophy, are recessive and require changes in both copies of the gene.
The symptoms and progression of DD can vary depending on the specific form of the disease. For example, in Welander distal myopathy, the arms are typically affected first, followed by the legs, while in Nonaka distal myopathy, the muscles near the shin are affected first, followed by muscle groups in the upper arms, upper legs, and neck. While the thigh muscles are usually spared in most forms of DD, some types, such as Miyoshi distal myopathy and hereditary inclusion-body myopathy type 2, can weaken the thigh muscles.
Managing DD often involves working closely with a healthcare team to provide physical therapy and supportive treatment. Early diagnosis and intervention are crucial to help slow the progression of the disease and maintain muscle function for as long as possible. While there is currently no cure for DD, ongoing research aims to understand better how gene defects affect protein abnormalities and muscle tissue in this diverse group of diseases.
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DD is caused by a mutation in genes that affect proteins necessary for muscle function
Distal muscles are those farthest away from the hips and shoulders, such as the hands, feet, lower arms, and lower legs. Distal muscular dystrophy (DD) is a group of rare diseases that primarily affect these distal muscles. It usually appears between the ages of 40 and 60 but can show up as early as the teenage years.
The mutations that cause DD affect the proteins made from the mutated genes, and these protein abnormalities, in turn, affect muscle tissue. Dystrophin, for example, is a protein complex that works to strengthen muscle fibers and protect them from injury as muscles contract and relax. It acts as an anchor, connecting each muscle cell's structural framework (cytoskeleton) with the extracellular matrix. Mutations in the gene encoding dystrophin can lead to reduced amounts or abnormal versions of the protein, resulting in muscle weakness and wasting. This is seen in conditions such as Duchenne and Becker muscular dystrophy, which are characterized by progressive muscle atrophy and a heart condition called dilated cardiomyopathy.
Research into the pathophysiology of dystrophic muscle and the discovery of new binding partners are paving the way for novel therapeutic strategies to treat this fatal muscle disease. Gene therapy, mutation correction using chimaeraplasts and short DNA fragments, exon skipping, and upregulation of other proteins are some of the approaches being explored to treat DD and other forms of muscular dystrophy.
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DD affects the muscles in the lower arms, hands, lower legs, and feet
Distal Muscular Dystrophy (DD) is a group of rare diseases that affect muscles in the body. DD affects the muscles in the lower arms, hands, lower legs, and feet. It causes a loss of muscle mass and strength, impacting the ability to grip objects, write, or type. It may also lead to difficulties in walking, with some forms of DD causing foot drop, making it challenging to lift the foot.
The lower arms, or forearms, contain several muscles that play a crucial role in various hand and wrist movements. These muscles can be classified as superficial or deep, depending on their proximity to the skin's surface. Superficial muscles on the underside of the forearm include the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, flexor digitorum superficialis, and pronator teres. In contrast, the brachioradialis, extensor carpi radialis longus and brevis, extensor digitorum communis, extensor digiti minimi, and extensor carpi ulnaris are found on the top of the forearm, beneath the superficial muscles. Deep muscles in the forearm include the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.
The hands also contain various intrinsic muscles that facilitate thumb and finger movements. These include the extensor digitorum brevis, which extends toes two through four, and the extensor hallucis brevis, aiding in extending the big toe.
The lower legs, or legs in general, consist of anterior, lateral, and posterior muscles. The anterior muscles, located in the front part of the lower leg, help lift and lower the foot and extend the toes. The lateral muscles, running along the outside of the lower leg, provide stability during walking and running and enable side-to-side foot movements. The posterior muscles, situated in the back of the lower leg, assist in flexing and pointing the toes, jumping, running, and pushing off into a sprint. They also contribute to maintaining good posture and supporting the arch of the foot.
The feet contain three main compartments: anterior, lateral, and posterior, each housing specific extrinsic muscles. The anterior compartment includes the extensor digitorum longus, extensor hallucis longus, and peroneus tertius muscles, which aid in toe extension and dorsiflexion of the foot. The lateral compartment is home to the peroneus longus and peroneus brevis muscles, facilitating eversion and plantarflexion of the foot. The posterior compartment contains the gastrocnemius, soleus, and plantaris muscles, collectively forming the calf muscles and enabling plantarflexion of the foot.
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The first symptom of DD is usually weakness in the distal muscles
Distal muscular dystrophy (DD) is a group of rare diseases that affect the muscles. The first symptom of DD is usually weakness in the distal muscles, which are those farthest away from the hips and shoulders, such as the hands, feet, lower arms, and lower legs. This weakness in the distal muscles is a result of progressive muscle wasting or atrophy, which causes the affected muscles to shrink and decrease in size.
The age of onset for DD can vary, with most cases appearing between ages 40 and 60, but some cases appearing as early as the teenage years. For example, Miyoshi distal myopathy typically affects people between the ages of 15 and 30, while Welander distal myopathy usually affects people between ages 40 and 50. Finnish distal myopathy, on the other hand, usually shows up after age 40.
The specific symptoms and progression of DD can vary depending on the subtype. For instance, in Miyoshi distal myopathy, the weakness begins in the calf muscles, while in Nonaka distal myopathy, it starts in the muscles near the shin before spreading to the upper arm, upper leg, and neck. In Welander distal myopathy, the arms are usually affected first, followed by the legs.
It's important to note that while DD affects the muscles, it does not impact cognition or intellect. However, as the disease progresses, other muscle groups may become affected, potentially leading to limited mobility and range of motion. In some cases, DD may affect the muscles used for speaking or swallowing, and in rare cases, it may even impact the heart.
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DD is inherited in an autosomal dominant pattern
Distal muscles are those farthest away from the hips and shoulders, such as the hands, feet, lower arms, and lower legs. Distal muscular dystrophy (DD) is a group of rare diseases that affect these distal muscles. It usually appears between the ages of 40 and 60 but can sometimes manifest as early as the teenage years.
In the case of DD, a change in only one copy of the gene is enough to cause most forms of the disease. This means that the disease passes down in a dominant manner. For example, in Finnish distal myopathy, people with one copy of the changed gene have a weakness in the muscles in the fronts of the lower legs (the tibial muscles) after age 40. However, people with Finnish DD who inherit two changed genes have muscle problems beginning in childhood, and they may need a wheelchair by age 30.
The inheritance pattern of autosomal dominance has several distinctive features. Males and females are affected in roughly equal proportions, and individuals in more than one generation are affected if the condition is inherited. Affected males and females are both able to pass the condition to their sons and daughters, with each child having a 50% chance of inheriting the condition. However, it is important to note that autosomal dominant disorders are usually rare and that chance has no memory. This means that the 50% chance of inheriting the altered gene for the condition applies to each child, regardless of whether the parents have already had children with or without the condition.
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Frequently asked questions
Distal muscles are those farthest away from the hips and shoulders, including the hands, feet, forearms, and lower legs.
Distal muscular dystrophy is a group of rare diseases that affect distal muscles. It usually appears between the ages of 40 and 60 but can show up as early as the teen years.
The first symptom of distal muscular dystrophy is typically weakness in the distal muscles. Over time, other muscle groups may be affected, and muscle mass in the affected regions may become visibly wasted. In some cases, the range of motion may be limited.
Distal muscular dystrophy is caused by a mutation in at least one of eight genes that affect proteins necessary for muscle function.
