Abstract
Myotonia congenital (MC) is the most common form of the hereditary nondystrophic myotonias caused by mutations in the skeletal muscle chloride channel gene (CLCN1) which change the functional features of muscle fibers membrane. MC is represented by two allelic forms with different types of inheritance: Thomsen’s myotonia congenita (TMC) with an autosomal dominant and Becker’s myotonia congenita (BMC) with an autosomal recessive inheritance. Both forms, TMC and BMC have the same clinical manifestation: skeletal muscle hypertrophy, transient weakness, generalized myotonia, debut in early childhood and a stationary development. Diseases are characterized by equal neurophysiological changes. In the family usually only one patient is detected. In some cases with the horizontal segregation diseases, more than one mutation in CLCN1 gene is found. These factors complicate the diagnosis of TMC and BMC, further medical and genetic counseling of the family members even after the patient’s genotype is detected. The confirmed BMC case with pseudo dominant type of inheritance and limited clinical manifestation is discussed in the light of differential diagnosis of the two discussed diseases.
Highlights
Myotonia congenital (MC) is the most common form of the hereditary nondystrophic myotonias caused by mutations in the skeletal muscle chloride channel gene (CLCN1) which change the functional features of muscle fibers membrane
MC is represented by two allelic forms with different types of inheritance: Thomsen’s myotonia congenita (TMC) with an autosomal dominant and Becker’s myotonia congenita (BMC) with an autosomal recessive inheritance
In some cases with the horizontal segregation diseases, more than one mutation in CLCN1 gene is found. These factors complicate the diagnosis of TMC and BMC, further medical and genetic counseling of the family members even after the patient’s genotype is detected
Summary
Случай миотонии Беккера с псевдодоминантным типом наследования: современные подходы к дифференциальной диагностике миотоний Томсена и Беккера. In some cases with the horizontal segregation diseases, more than one mutation in CLCN1 gene is found These factors complicate the diagnosis of TMC and BMC, further medical and genetic counseling of the family members even after the patient’s genotype is detected. Предъявлял жалобы на непродолжительную скованность скелетных мышц при первых движениях, усиление скованности на холоде, периоды слабости после длительной физической нагрузки Первый признак заболевания – скованность в мышцах при начале движений – был обнаружен в 7–8 лет. Жалобы и неврологический статус аналогичные пробанду, незначительно менее вы ражен миотонический компонент при биципитальном рефлексе, миотоническая ямка с дельтовидной и четырехглавой мышц бедра до 3–4 с. Жалобы и неврологический статус аналогичные пробанду, при этом отмечена меньшая выраженность активных и механических миотонических феноменов (активный миотонический феномен в кистях полностью проходит после 2–3 форсированных мышечных сокращений). Обсуждение Дифференциальная диагностика отдельных форм наследственных миотонических синдромов (НМС) – непростая задача, и дискуссии о выборе алгоритма
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