特異な筋組織所見を示したBenign congenital hypotonia

抄録

An unusual case of benign congenital myopathy was presented.
A boy of eight years of age has had motor retardation and difficulties in climbing stairs since the early stage of his infancy. When he was 4 years old, neurological examination revealed proximal muscular weakness, hypotonia and positive Gowers' sign. Deep tendon reflexes were all absent, and pseudohypertrophy of calf muscles were not detected. His mantality was normal. CPK level was not elevated. He was followed up by the authors during five years after the first examination. He had shown a distinct recovery course.
When he was 8 years old, he was admitted to Kyushu-Koseinenkin Hospital. The principal findings on admission were as follows; 1) very mild weakness and hypotonia in extremities (proximal weakness) 2) diminished deep reflexes (not absent) 3) no fasciculations 4) slender constitution 5) no pseudohypertrophy of any muscle, no contractures of joints. Serum enzyme levels (CPK, Aldolase, GOT, GPT, LDH) was not elevated. Electromyography revealed relatively prominent low amplitude potentials with short durations as well as polyphasic units and no spontaneous discharges nor giant motor units.
Muscle biopsy specimen taken from the right rectus femoris was studied with the light microscope and with the electron microscope. The diameter of the muscle fibers on the frozen sections was found to be normal. The checker board of fiber types showed normal appearance. The increase of endomysial connective tissue were unremarkable. There were no increase of subsarcolemmal nucleus and central nuscleus. In modified Gomori's trichrome staining rod-body was observed in a few muscle fibers. These inclusion bodies corresponds to the fine structure of nemaline body by the electron microscopy. And another unestablished cytoplasmic inclusion body was observed. Several cylindrical, when sectioned transversely, inclusion bodies composed of 10 to 20 concentric filaments ware accumulated in the subsarcolemmal region. There were no mitochondrial abnormalities or abnormality of glycogen granules. In some muscle fiber, focal myofibrillar degenerations were noted by electron microscopic study.
Clinically, the present case is very similar to the reported cases of “Benign congenital hypotonia (Walton) ”. But there are no report of “benign congenital hypotonia (Walton) ” with a few rod-body and unusual cytoplasmic inclusions in the biopsied muscle.