Progressive muscular dystrophy

Japanese: 進行性筋ジストロフィー症 - しんこうせいきんジストロフィーしょう（英語表記）Progressive muscular dystrophy

What is the disease?

Muscle fiber Necrosis ( Replying to @sarah_mcdonald ) - Regeneration is the main lesion, and clinically, progressive muscle weakness and atrophy ( Ishku ) It is a hereditary disease that results in

Depending on the inheritance pattern, there are sex chromosomal recessive Duchenne type (severe type), Becker type (benign type), and autosomal recessive Retinaculum ( I want to ) type (some are dominant), Fukuyama type, and autosomal dominant Face, shoulder, upper arm ( Hard-working industrial worker ) In Japan, the most common types are Duchenne and Fukuyama.

What is the cause?

It is a genetic abnormality. The causative gene is often an abnormality in a protein that constitutes a structure related to the mutual adhesion between the plasma membrane on the surface of skeletal muscle fibers and the basement membrane that surrounds it, such as dystrophin.

Below, we will explain the typical Duchenne type. This type is inherited through sex chromosome recessive inheritance and affects boys, with an incidence rate of 1 in 3,500 male births.

How symptoms manifest

There are no obvious symptoms in infancy, and the child does not begin to walk significantly later. Usually, symptoms become noticeable around the age of 3 to 5 when the child begins to fall easily or is unable to run.

Muscle weakness is most prevalent in the proximal muscles of the limbs (the muscles close to the trunk of the thighs and upper arms), and Prone position ( Fukugai ) I put my hands on the floor. buttocks ( Denbu ) First, the child raises his/her knees and then places his/her hands on his/her knees and climbs up. Contracture ( Education ) For Sharp feet ( Sensoku ) The child will then start walking (on his toes).

Pseudohypertrophy is seen in the calf of the lower leg. Pseudohypertrophy is not muscle, but is caused by an increase in fat and connective tissue, which makes the calf thicker.

Many children become unable to walk by age 8 to 10, but muscle strength is relatively preserved in the distal muscles of the limbs (muscles far from the trunk in the lower legs and forearms). Muscle atrophy becomes more pronounced in the trunk and proximal muscles of the limbs.

After puberty, muscle weakness progresses, and the patient is unable to move anything except for the fingertips, requiring full assistance in daily life. Gastrostomy ( Color ) However, due to weakening of the respiratory muscles, artificial respirator management is required.

Testing and diagnosis

Blood tests show elevated levels of creatine kinase, a muscle enzyme. Electromyograms show myogenic changes. Muscle biopsies show histological changes, with repeated necrosis and regeneration of muscle fibers.

The definitive diagnosis is made by genetic testing to confirm a deletion of the dystrophin gene.

Treatment methods

Drug therapy, gene therapy, and stem cell transplantation are being researched as fundamental treatments, but they are not yet at the stage of practical application.

At this time, it is important to perform appropriate rehabilitation and prevent complications. Rehabilitation should be performed according to the progression of symptoms, walking should be continued as much as possible, stability in standing and sitting positions and respiratory function should be maintained, and environmental improvements should be made to improve the patient's quality of life. The main treatment for complications is management of cardiac and respiratory failure.

With the widespread use of artificial ventilators, the number of deaths from respiratory failure has dropped dramatically, but the number of deaths from heart failure is increasing, and the average life expectancy remains short at 30 years.

What to do if you notice an illness

First, please visit a nearby pediatrician. After a diagnosis, ask them to introduce you to a specialized facility with an attached school that can treat children with the same disease, and consider sending your child to school.

Masashi Fujii

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　筋線維の壊死(えし)・再生を主病変とし、臨床的には進行性の筋力低下と筋萎縮(いしゅく)を来す遺伝性の病気です。

　遺伝形式により、性染色体劣性遺伝のデュシェンヌ型（重症型）、ベッカー型（良性型）、常染色体劣性遺伝の支帯(したい)型（一部は優性遺伝）、福山型、そして常染色体優生遺伝の顔面肩甲上腕(がんめんけんこうじょうわん)型に分類されます。日本では、デュシェンヌ型や福山型が多い型です。

原因は何か

　遺伝子の異常です。原因遺伝子は、ジストロフィンなどのように骨格筋の筋線維表面の形質膜と、それを取り巻く基底膜との相互の接着に関係する構造体を構成する蛋白の異常症である場合が多くみられます。

　以下、代表的なデュシェンヌ型について述べます。この型の遺伝形式は性染色体劣性遺伝で、男児に発症し、発生率は出生男児3500人に1人です。

症状の現れ方

　乳児期には明らかな症状はみられず、歩き始める時期が大きく遅れることはありません。通常、3～5歳ころに転びやすい、走れないなどの異常で気づきます。

　筋力低下は、四肢近位筋（大腿や上腕の体幹に近い筋肉）に多く、立ち上がる時に一度腹臥位(ふくがい)となり、床に手をついて臀部(でんぶ)を上げ、次に手を膝に当てて体をよじ登るように起立する「登はん性起立」がみられるようになります。足関節の拘縮(こうしゅく)のため尖足(せんそく)歩行（つま先歩き）になってきます。