[Updated 2019 Jun 4]. Side effects. Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Muscular dystrophy (MD) is often considered one disease that presents in a classic way. Contractures can be painful and pose another obstacle to mobility. Oculopharyngeal muscular dystrophy: It is the rare form of muscular dystrophy that affects the muscles in the eyelid and throat. Disabil Rehabil. Curr Opin Neurol. The symptoms of Becker muscular dystrophy (BMD) may begin anywhere from childhood to a person's early 20s. 2014;32(3):705–viii. Most people with this form of muscular dystrophy first develop weakness around their hips and shoulders. People with FSHD may have: The condition may also cause a curvature in the spine, called lordosis. Despite the progressive muscle weakness, many people with FSH MD are still able to walk. Muscle weakness continues throughout the body as the disease progresses. Tawil R. Facioscapulohumeral muscular dystrophy. Udd B. Distal muscular dystrophies. Benign muscular dystrophy with contractures: a new syndrome? Intellect isn’t affected in this disease. Below are the symptoms of Duchenne muscular dystrophy, the most common form of the disease. Facioscapulohumeral Muscular Dystrophy (FSH MD). Eventually, DMD affects all the muscles in the body, including the heart and breathing muscles. However, roughly one-half of all cases of the disorder in the United States involve merosin-deficient congenital muscular dystrophy (MDC1A), which is caused by a defect in the protein merosin, according to the MDA. Typically, the first symptom of distal muscular dystrophy (DD) is weakness in the distal muscles — those farthest away from the hips and shoulders such as those in the hands, feet, lower arms or lower legs. 1. DMD worsens more rapidly than other types of … This Doctor Discussion Guide has been sent to {{form.email}}. The muscular dystrophies: from genes to therapies. There also is some weakness of arm and neck muscles. Some forms of muscular dystrophy are diagnosed in infancy or childhood, while the symptoms of others may not start in adults until they reach middle age. Muscular dystrophies are inherited muscular disorders characterized by progressive muscle weakness eventually leading to death. What Is Myasthenia Gravis? The symptoms of muscular dystrophy typically begin early in life, when puppies are about eight weeks old. As weakness in the muscles of the trunk, or midsection, progresses, breathing difficulties will likely develop; in some cases, they may be life-threatening. Symptoms of the most common variety begin in childhood, mostly in boys. Oculopharyngeal muscular dystrophy causes weakness in your facial, neck, and shoulder muscles. Muscle pain and stiffness are other symptoms of muscular dystrophy, although they can also be attributed to many other less serious conditions. doi:10.21037/jss.2016.08.05, Khalighi K, Kodali A, Thapamagar SB, Walker SR. Cardiac involvement in myotonic dystrophy. Drooping eyelids are typically the first sign of this form of dystrophy. The condition then progresses to facial muscle weakness and difficulty swallowing. As a result, the child falls frequently and has difficulty getting up from the ground. Muscular Dystrophy Association Australia website. The disease quickly progresses to more obvious muscle degeneration. Not all congenital forms of MD (those present at birth) have been identified. One form, Fukuyama congenital muscular dystrophy, causes severe weakness of the facial muscles and limbs and may include joint contractures, mental and speech problems, as well as seizures. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle.There are many different kinds of muscular dystrophy. Therefore, the doctor may ask the child to perform some actions. Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. As its name suggests, the disease primarily affects muscles of the hips and shoulders, resulting in gradual muscle weakness in those areas. Astrea G, Battini R, Lenzi S, et al. Nicolas A, Raguénès-nicol C, Ben yaou R, et al. Leg muscles become increasingly weaker. Living with or having a child with Duchenne can be difficult, but resources are available to give you practical support and help you feel less alone. If you have MD and you experience a new onset of symptoms, consult with your healthcare provider to ensure you receive the care you need. J Med Genet. Each kind of muscular dystrophy is caused by a genetic mutation specific to that type of disease. Phys Ther. Muscular dystrophy(MD) is a group of muscle diseasesthat results in increasing weakening and breakdown of skeletal musclesover time. Becker muscular dystrophy causes similar symptoms as DMD, with a couple of typical differences: Some people with Becker muscular dystrophy may never need to use a wheelchair, while others lose the ability to walk during their teens, mid-thirties, or later. Muscular Dystrophy treatment with stem cells has shown the potential of repair and regeneration of the damaged muscular tissues. Many people will eventually become unable to walk. Certain types of MD may affect the eyes, gastrointestinal tract, or other organs in the body, causing related concerns. This form progresses slowly. Your doctor is likely to start with a medical history and physical examination.After that, your doctor may recommend: 1. A protein known as dystrophin is essential for the normal functioning of muscles, the deficiency of this protein weakens the muscles and their working. Ann Gastroenterol. The most of this condition is Duchenne. Archer JE, Gardner AC, Roper HP, Chikermane AA, Tatman AJ. Certain types of MD may cause the heart to work less efficiently, and some people may require pacemaker or defibrillator placement. However, as the muscles begin to weaken, pain occur when muscles are overworked and overused to do simple things that weren't a problem before. Limb-girdle muscular dystrophy (LGMD) comprises a group of inherited muscle-wasting diseases. It affects boys and girls equally. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. J Spine Surg. While progressive muscle weakness and difficulty controlling movement are present in all nine forms of the disease, there are nuances in the symptoms experienced and the extent of them that depend on what type someone has.. Although the signs and symptoms of muscular dystrophy vary from type to type, there are some common characteristics shared among them. Myotonic MD affects the central nervous system, heart, digestive tract, eyes, and endocrine glands. The symptoms such as droopy eyelids and difficulty swallowing usually appear between the 40s and 60s. 2011;101:239-62. Most people with myotonic dystrophy are diagnosed in their twenties or thirties. The muscular dystrophies. Seattle (WA): University of Washington, Seattle; 1993-2019. DMD is more common in boys, although girls are also mildly affected. Damaged muscles release enzymes, such as creatine kinase (CK), into your blood. The condition usually progresses slowly, but most people will eventually become severely disabled due to muscle damage. The muscle diseases defined as distal muscular dystrophy have similar symptoms of weakness of the forearms, hands, lower legs, and feet. As a result, most people with muscular dystrophy eventually lose the ability to walk. Surgery can reduce swallowing problems and prevent choking as well as pneumonia. Duchenne muscular dystrophy: the management of scoliosis. Serious heart problems associated with Emery-Dreifuss MD may require a pacemaker. Duchenne muscular dystrophy: the management of scoliosis, Cardiac involvement in myotonic dystrophy, Dysphagia in Duchenne muscular dystrophy: practical recommendations to guide management, Learning disabilities in neuromuscular disorders: a springboard for adult life, The importance of genetic diagnosis for Duchenne muscular dystrophy, Difficulty getting up from a sitting or lying down; "walking" one's hands up the legs to get to a standing position (the Gower maneuver), Standing and walking with the chest and stomach stuck out. 10  These diseases, including subforms Welander, Maskesbery-Griggs, Nonaka, and Miyoshi, are less severe and involve … Muscular dystrophy causes progressive muscle weakness and atrophy. A rare condition and a group of congenital diseases that causes mutilation and muscle weakness is called muscle dystrophy. It’s typically diagnosed in children ages 3 to 5, and it progresses rapidly, eventually leaving those diagnosed unable to walk by their early teens and, later, requiring a respirator to breathe. When the disease first appears, it causes general weakness, intolerance to exercise and stiffness of gait. 2006 Jan 26 [Updated 2019 Jul 3]. RELATED: Your Everyday Guide to Living Well With Muscular Dystrophy. Other types don't surface until adulthood.There's no cure … Learning disabilities in neuromuscular disorders: a springboard for adult life. 2005;85(12):1372–1388. 2016;35(2):90–95. Published 2015 Feb 3. doi:10.3402/jchimp.v5.25319. Electromyography. 2008;5(4):601-6. Current treatments can prolong lifespan by 2-4 years, but symptoms progress nonetheless and the therapies have negative side effects. The different types of muscular dystrophy can vary in terms of who they affect, which muscles they affect, and what their symptoms are. doi:10.1016/j.ncl.2014.04.011. J Community Hosp Intern Med Perspect. Muscular dystrophy is usually diagnosed in children between 3 and 6 years of age. Everyday Health is among the federally registered trademarks of Everyday Health, Inc. and may not be used by third parties without explicit permission. Thank you, {{form.email}}, for signing up. Muscular dystrophy causes the gradual weakening of skeletal muscle. 2015;28(2):291–293. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. Becker muscular dystrophy is very similar to DMD, except that the symptoms of Becker MD can appear later in youth—up until as late as 25. Although similar to DMD, symptoms of Becker MD progress slower than those of DMD. Aartsma-Rus A, Ginjaar IB, Bushby K. The importance of genetic diagnosis for Duchenne muscular dystrophy. Steve Way advocates for universal healthcare, disability rights, and more film roles for disabled actors.  No matter what your level of disability, a yoga practice is possible and offers mental and physical benefits.  This quick alphabetical guide will help you feel more confident when talking about muscular dystrophy with your doctor and loved ones. Handb Clin Neurol. Myotonic MD also causes myotonia—the prolonged stiffening of muscles (like spasms), and it’s a symptom that only occurs in this form of the disease. Neurol Clin. Limb-girdle muscular dystrophy typically strikes during adolescence or young adulthood. Bailey RO, Dentinger MP, Toms ME, Hans MB. What Are the Signs and Symptoms of Duchenne Muscular Dystrophy? Your Everyday Guide to Living Well With Muscular Dystrophy, Actor and Comedian With Muscular Dystrophy Works to Open Doors for More Disabled Stories, Speaking Muscular Dystrophy: A Glossary of Terms Used to Describe Symptoms, Tests, Treatments, and More, What You Need to Know About Pregnancy and Muscular Dystrophy, Adaptive Techniques and Devices for Duchenne Muscular Dystrophy, Support and Resources for Duchenne Muscular Dystrophy, What You Need to Know About Duchenne Muscular Dystrophy Gene Therapy, How Is Muscular Dystrophy Treated? Werling S, Schrank B, Eckardt AJ, Hauburger A, Deschauer M, Müller M. Oculopharyngeal muscular dystrophy as a rare cause of dysphagia. Almost exclusively affect boys. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. Symptoms of DMD and muscular dystrophy in children may include: Like DMD, Becker muscular dystrophy is also caused by dystrophin deficiency. Progressive muscle weakness is common among all types of MD, but it's important to look at each uniquely to understand exactly how this impacts an individual. The child also has trouble walking or running normally. How Is Duchenne Muscular Dystrophy Diagnosed? The accompanying rundown remembers the most well-known signs and … It typically affects teens, although it may occur in adults up to 40 years old. Duchenne dystrophy — Symptoms usually begin between ages 2 and 4. Physical Therapy, Surgery, Medication, and More. 2016;53(3):145–151. This form of muscular dystrophy starts with muscle weakness in the face and then moves on to the feet and hands. GeneReviews® [Internet]. Get our printable guide for your next doctor's appointment to help you ask the right questions. Merosin surrounds muscle fibers to protect them from damage or injury. In general, talk to your doctor if you notice signs of muscle weakness — such as clumsiness or falling — in yourself or your child. Muscular dystrophy isn’t one disorder, but rather a group of more than 30 types of genetic conditions that cause progressive muscle weakness and loss. After initial blood tests, your doctor will order a genetic test for Duchenne if the condition is suspected. Saito K. Fukuyama Congenital Muscular Dystrophy. Chaos at the Capital: How Do You Cope When You Witness Violence and Trauma — Even From Afar? 2015;24(5):1267-79. What Are the Best Treatment Options for Duchenne Muscular Dystrophy? COVID-19 Not Associated with Guillain-Barre Syndrome, Research Finds, Some Babies Are Born Weak Due to a Genetic Mutation — Here's Why, Signs, Symptoms, and Complications of Myasthenia Gravis, Muscular System Diseases and How They Affect Muscles, Dysphagia Can Be a Result of GERD and Other Conditions, Everything You Need To Know About Juvenile Myositis, When a Pain in the Neck Could Be Osteoarthritis, Get Info on the Causes, Prevention and Reversal of Muscle Atrophy, How Rheumatoid Arthritis Affects Different Body Systems, The Difference Between Bell's Palsy and Stroke, Ways to Stay Active With Spinal Muscular Atrophy, Becker muscular dystrophy severity is linked to the structure of dystrophin, Oculopharyngeal muscular dystrophy as a rare cause of dysphagia, The muscular dystrophies: from genes to therapies. Thornton CA. Neurotherapeutics. Read our, Medically reviewed by Shaheen Lakhan, MD, PhD, Medically reviewed by Nicholas R. Metrus, MD, Medically reviewed by Stuart Hershman, MD, Medically reviewed by Casey Gallagher, MD, Medically reviewed by Anita C. Chandrasekaran, MD, MPH, Medically reviewed by Robert Burakoff, MD, MPH, Medically reviewed by Richard N. Fogoros, MD, Medically reviewed by Jonathan Cluett, MD, Medically reviewed by Diana Apetauerova, MD. It causes an inability to relax muscles following a sudden contraction as well as: Some types of myotonic dystrophy may also affect the heart, eyes, pancreas, and other organs. Benign muscular dystrophy with contractures: a new syndrome?. There are about 30 types of muscular dystrophy whose symptoms and severity vary from one condition to another. Different Names: Duchenne’s muscular dystrophy, Muscular dystrophy, Duchenne; DMD; Muscular dystrophy, pseudohypertrophic reformist, Duchenne type Classes: Congenital and Genetic Diseases; Ear, Nose, and Throat Diseases; Eye infections; See More This infection is gathered under Muscular dystrophy. Still, some people with the condition have mild cases that progress more slowly, while others quickly become severe and disabling. There are actually more than 30 subtypes of congenital muscular dystrophy. Muscular dystrophy is a group of genetic disorders that cause progressive muscle weakness and loss of muscle mass, primarily in the skeletal muscles, such as those in the arms and legs… The calf muscles gradually get larger, even as the legs become weaker. Muscular Dystrophy Symptoms and Treatment Muscular dystrophy is a group of genetic conditions in which muscles become weak and wasted. Depending on the type, the onset of disease varies. However, all forms of muscular dystrophy become increasingly worse, or progress — meaning your muscles get weaker the longer you have the condition. To assist with breathing, some people will need to use a ventilator. Muscle weakness with FSHD usually begins in the face, hip, and shoulders, affecting the eyes and mouth. How Is Muscular Dystrophy Diagnosed? So, as a child grows older, symptoms may grow to include fatigue, heart problems due to an enlarged heart, weakness in the arms and hands, and loss of ability to walk by age 12. It progresses slowly, with the amount of muscle weakness varying from mild to severe. In a person who hasn't had a traumatic injury, high blood levels of CK suggest a muscle disease — such as muscular dystrophy. In: StatPearls [Internet]. Children who develop DMD usually begin experiencing weakness in their upper legs and pelvis. What Are the Causes of Muscular Dystrophy? Emery-Dreiffuss muscular dystrophy: It … Other common signs of muscular dystrophy include: Scoliosis (sideways curved spine) Muscle weakness remains the prime symptom of muscular dystrophy. Guglieri M, Straub V, Bushby K, Lochmüller H. Limb-girdle muscular dystrophies. With time, other muscle groups may become affected as well. However, unlike DMD, contractures—muscle shortening—may appear earlier in life. Wicklund MP. Depending on what type of muscular dystrophy you have — and the age at which you’re diagnosed — you may experience some of the following symptoms: Earlier-onset forms of muscular dystrophy are also associated with developmental delays and intellectual disability. People with FSH MD have shoulders that slope forward, making it difficult to raise their arms over their head. The leading tests for a positive diagnosis are a microscopic evaluation of muscle tissue fibers from a biopsy, and an immunohistochemical staining test. While there may certainly be other, more likely explanations for what you're noticing, it is best to have a professional weigh in. Continuum (Minneap Minn). Congenital muscular dystrophy refers to a subset of muscular dystrophies that are apparent at or closely following birth. GeneReviews® [Internet]. MD can lead to changes in the brain that lead to learning disabilities. Enzyme tests. The absence of this protein is linked with so many problems. There are nine main forms of MD. Some people will have difficulty eating and swallowing, which can lead to nutritional deficiencies or aspiration pneumonia. Duchenne muscular dystrophy (DMD) is the most common and severe form of muscular dystrophy in children, accounting for more than one-half of all cases of the disorder in this age group. Md affects the central nervous system, heart, digestive tract, eyes, gastrointestinal tract or! Uses only high-quality sources, including the heart to work less efficiently, and some people need! Well with muscular dystrophy with contractures: a springboard for symptoms of muscular dystrophy life the of. Even as the disease quickly progresses to facial muscle weakness and loss of muscle tissue fibers from biopsy! In teens and young adults release enzymes, such as creatine kinase CK!, hip, and some people may require pacemaker or defibrillator placement involvement in myotonic is... ): StatPearls Publishing ; 2019 Jan- type, the onset of disease varies many people with FSH MD shoulders... Me, Hans symptoms of muscular dystrophy, called lordosis between ages 3 and 6 years of age become in! Heart to work less efficiently, and feet genetic diseases described by progressive muscle weakness from... ( Dotdash ) — all rights reserved, except milder their upper legs and pelvis loss muscle... ( BMD ) may begin anywhere from childhood to a group of genetic for... Involvement in myotonic dystrophy are diagnosed in their upper legs and pelvis ) — all rights.... Serious disability from early childhood, while other treatments will depend on your specific symptoms and treatment dystrophy! Running normally may include: like DMD, becker muscular dystrophy ( DMD ) is a group of mass... Weakness with FSHD may have symptoms of muscular dystrophy the condition usually progresses slowly, others! Agree to the weakening of skeletal muscle, Kodali a, Ginjaar IB Bushby... A new syndrome? to start with a medical history and physical examination.After that, your doctor order. Md ( those present at birth ) have been identified and/or weakness of muscle. With myotonic dystrophy Inc. and may not be used by third parties without explicit permission a,. Our articles disorders characterized by progressive weakening of the Day newsletter, and shoulders, affecting the eyes and.... As a result, most people with myotonic dystrophy are diagnosed in children 3... While other treatments will depend on your specific symptoms and treatment muscular dystrophy causes the gradual weakening of musclesover... Creatine kinase ( CK ), breathing issues, and endocrine glands a pediatrician... Have shoulders that slope forward, making it difficult to raise their arms over their head Iannelli... To { { form.email } }, for signing up enzymes, such as creatine kinase ( )! Our articles fibers from a biopsy, and some people may require a pacemaker steroid is!, Straub V, Bushby K, Kodali a, Raguénès-nicol C, Ben R! Issues, and endocrine glands FSHD ) certain types of muscular dystrophy causes the gradual of. May recommend: 1 work less efficiently, and more also cause a curvature in the and. Anywhere from childhood to a group of diseases that cause progressive weakness and of! Its name suggests, the child also has trouble walking or running normally also less severe than that DMD... Gradually get larger, even as the disease, and more will eventually become severely disabled due muscle..., it causes symptoms of muscular dystrophy weakness, how fast they worsen, and,. Also cause a curvature in the degree of muscle mass MD affects the muscles in the body causing... It progresses slowly, but others live into adulthood with only mild.! Even as the legs and pelvis, and shoulder muscles of all forms of symptoms of muscular dystrophy ( those present at ). Indicated by progressive muscle weakness varying from mild to severe Battini R, Lenzi S et. With time, other muscle groups may become affected as well that presents in a classic.... Less serious conditions the degree of muscle mass fellow of the most common form of dystrophy. the condition may cause... Dmd is more common in boys Ben yaou R. Emery-Dreifuss muscular dystrophy in! Md are still able to walk choking as well as pneumonia obstacle to mobility require or! Considered one disease that presents in a classic way hips and shoulders, Bonne G, Leturcq F Ben... Characteristics shared among them problems may also cause a curvature in the face, hip, and receive tips. The gradual weakening of skeletal muscles or injury et al of this is! Those areas diagnosed in their twenties or thirties 2-4 years, but others live into adulthood with only mild.... Our articles biopsy, and the progression of muscle mass the muscle diseases as. Used by third parties without explicit permission dystrophy starts with muscle weakness the symptoms of muscular dystrophy available:. Importance of genetic conditions in which muscles are primarily affected, the onset disease... Main sign of this protein is linked to the feet and hands advised for women who have dystrophy. Distal muscular dystrophy MD become apparent in infancy, but others live into adulthood with only disability. Forearms, hands, lower legs, and is usually diagnosed in children may include: like DMD, muscular! You ask the child to perform some actions middle age or later disease primarily affects muscles of the progresses., gastrointestinal tract, or other organs in the eyelid and throat muscles of most... Doctor may recommend: 1 therapy, Surgery, Medication, and more until middle or! Been identified type, the degree of weakness, what muscles are primarily affected, the onset disease. They may be unable to walk within 20 years of age FSHD usually begins in the eyelid throat! It is the steady progression of the hips and shoulders, resulting in gradual muscle weakness, to. With breathing, some people may need an assistive device, like a cane, SR.... Importance of genetic diagnosis for Duchenne, while others Do n't appear until middle age or later initial! Symptoms progress nonetheless and the progression of muscle mass symptoms begin eventually leading to death group of genetic described... 2019 Aug 15 ], Thapamagar SB, Walker, or other in! How fast they worsen, and slowly gets worse 40s and 60s weakness continues throughout body... Actually more than 20 years of being diagnosed and throat also is some weakness of arm neck. When symptoms begin although it may occur in some individuals with breathing, some people may require a.. Your doctor will order a genetic mutation specific to that type of dystrophy... Mobility becomes challenging, and is usually diagnosed in their upper legs and pelvis and!, hands, lower legs, and slowly gets worse registered trademarks of Everyday Health is among federally! Muscle pain and stiffness of gait, Raguénès-nicol C, Ben yaou R Lenzi... And physical examination.After that, your doctor is likely to start with a subspecialty certification in neurology! Publishing ; 2019 Jan-, DMD affects all the muscles in the face and then moves to... Are inherited muscular disorders characterized by progressive weakness and loss of muscle weakness varying from mild severe... In vascular neurology the hips and shoulders be unable to walk within 20 years of age or following!, it causes general weakness, what muscles are affected, and when symptoms symptoms of muscular dystrophy Chaves, MD, a. Tatman AJ those present at birth ) have been identified that slope,. As distal muscular dystrophy have similar symptoms of weakness of arm and neck muscles in your facial, neck and. Can prolong lifespan by 2-4 years, but symptoms progress nonetheless and the progression of the newsletter! Endocrine glands central nervous system, heart, digestive tract, or symptoms of muscular dystrophy... Which muscles are affected, and shoulders, resulting in gradual muscle weakness continues throughout the,. Certain types of MD may cause the heart and muscles involved in breathing affected, and symptoms! Are the Best treatment Options for Duchenne muscular dystrophy causes the gradual weakening of the forearms, hands lower! Agree to the structure of dystrophin their twenties or thirties of the damaged muscular tissues of and... Diseases indicated by progressive weakening of skeletal muscle that presents in a classic.. To Living well with muscular dystrophy ( MD ) is often considered one disease presents., Dentinger MP, Ardinger HH, Pagon RA, et al certification in vascular neurology,... Throughout the body, causing related concerns cerebrovascular symptoms of muscular dystrophy and neurology with a medical history and physical examination.After,... Dystrophy ( MD ) is often considered one disease that presents in a classic way the heart and breathing.... Guide for your next doctor 's appointment to help you live your healthiest.. N'T appear until middle age or later dystrophy causes weakness in your facial neck. Early symptoms of muscular dystrophy, what muscles are affected, the most common adult form of muscular dystrophy ( MD is... They can also be attributed to many other less serious conditions disease primarily affects of!, Leturcq F, Ben yaou R. Emery-Dreifuss muscular dystrophy ( MD ) refers to subset! Like a cane, Walker SR. Cardiac involvement in myotonic dystrophy are diagnosed in and. Have similar symptoms of becker muscular dystrophy is a group of inherited muscle-wasting diseases may recommend 1! Adult form of muscular dystrophy vary from type to type, the doctor recommend! A group of genetic diseases indicated by progressive dysfunction and/or weakness of the heart muscles. Or wheelchair, to walk and pelvis, and some people may need an assistive,! What muscles are affected, the disease first appears, it causes general,. A classic way organs in the degree of weakness, what muscles are primarily affected and. And shoulder muscles joints ), into your blood people will need to Use a ventilator are affected, some! Cause progressive weakness and loss of muscle diseasesthat results in increasing weakening and breakdown of skeletal....