Dystrophin抗体染色により診断した30歳発症のBecker型筋ジストロフィー孤発例

A Rare Case of Adult-Onset Becker Muscular Dystrophy Diagnosed by Dystrophin Staining

　30歳という成人期に発症したBecker型筋ジストロフィー（MD）の稀な症例を報告した。症例は30歳より下肢近位の筋力低下で発症し，緩徐進行性であるが54歳の現時点でも独歩可能であった。本例では遺伝歴が明らかでない男子孤発例であったため肢帯型MDとの鑑別が困難であった。生検筋の抗dystrophin抗体染色で"faint and patchy pattern"を示し，immunoblotで分子量380kdの異常dystrophinを検出し，Becker型MDと確定診断した。Becker型MDと肢帯型MDとの鑑別は遺伝相談や予後予測に関わるため重要であり，本例のような症例では"dystrophin診断"が必要であると考えられた。

Different diagnosis of Becker muscular dystrophy (MD) from limb-girdle MD mainly depends on the differences of heredity form and age at onset. However, sporadic cases with either type of MD often occur, and occasionally Becker MD can occur in adult age when limb-girdle MD commonly occurs. We reported the male sporadic case of Becker MD with the onset at 30 year old who was diagnosed by dystrophin staining. At the age of 30, he noticed mild difficulty to stand up and instability when hurrying up stairs. His weakness of lower limb-girdle gradually progressed, but he is able to walk without any support at the present age of 54, and he never showed weakness in upper limbs. Neurological and laboratory examination revealed that severe atrophy of lower limb-girdle, mild calf hypertrophy and moderate elevate of serum CK level. These history and symptoms hardly distin-guish between Becker and limb-girdle MD. Im-munostaining of biopsy muscle from the patient using the antiserum against synthetic peptide frag-ment of dystrophin revealed faint and patchy pat-tern, and immunoblot revealed 380 kd of abnormal size dystrophin. These dystrophin testing confirmed that this case was a rare case of Becker MD with adult-onset and mild clinical course.