Itaya Kazuhiro, Inoue Manabu, Iwanami Hiroaki, Oonaka Youhei, Jimi Takahiro, Ichikawa Hiroo
Department of Neurology, Showa University Fujigaoka Hospital.
Rinsho Shinkeigaku. 2015;55(4):254-8. doi: 10.5692/clinicalneurol.55.254.
A 65-year-old man first visited our hospital due to hypercreatinekinasemia (hyperCKemia) (669 IU/l) 12 years ago at age 53. At that time, he had normal muscle strength without other neurological deficits, electromyography (EMG) was normal, and a muscle biopsy obtained from the biceps brachii was intact in routine histochemical studies. These findings led to a diagnosis of idiopathic hyperCKemia that lasted for over a decade. At age 65, the patient became aware of muscle weakness and serum CK was elevated to 4,846 IU/l. Neurological examination revealed very mild atrophy in both thighs, proximal muscle weakness in the left upper and right lower limbs without myalgia, grasping pain, joint pain, and skin lesions. A typical myogenic pattern was detected on EMG exclusively in proximal limb muscles, and fat-suppressed MRI showed high intensity signal areas in adductor magnus muscles. The clinical diagnosis was limb-girdle muscular dystrophy, but MRI findings suggestive of an inflammatory process prompted us to perform muscle biopsy at the rectus femoris. The pathology had characteristic features of necrotizing myopathy containing necrotic and regenerating fibers without prominent inflammatory cell infiltration. Serum anti-signal recognition particle (SRP) antibodies were found to be positive and the final diagnosis was anti-SRP antibody myopathy. Muscle weakness progressed slowly despite therapy with oral corticosteroids. Addition of intravenous high-dose immunoglobulin therapy led to an apparent improvement of muscle weakness in parallel with lowering of the serum CK level. In those who were thought to be idiopathic hyperCKemia or hereditary muscle disorders, potential immunotherapy-effective group does exist. We suggest considering such cases including anti-SRP antibody myopathy during diagnosis, and non-invasive MRI study may be useful to differentiate immunotherapy-effective group from hereditary muscle disorders.
一名65岁男性12年前，即53岁时因高肌酸激酶血症（高CK血症）（669 IU/l）首次就诊于我院。当时，他肌力正常，无其他神经功能缺损，肌电图（EMG）正常，肱二头肌肌肉活检的常规组织化学研究结果正常。这些发现导致诊断为特发性高CK血症，持续了十多年。65岁时，患者出现肌肉无力，血清CK升高至4846 IU/l。神经学检查发现双侧大腿非常轻微萎缩，左上肢和右下肢近端肌肉无力，无肌痛、抓握痛、关节痛和皮肤病变。EMG仅在肢体近端肌肉检测到典型的肌源性模式，脂肪抑制MRI显示大收肌有高强度信号区。临床诊断为肢带型肌营养不良，但MRI表现提示有炎症过程促使我们对股直肌进行肌肉活检。病理具有坏死性肌病的特征，包含坏死和再生纤维，无明显炎性细胞浸润。血清抗信号识别颗粒（SRP）抗体呈阳性，最终诊断为抗SRP抗体肌病。尽管使用口服糖皮质激素治疗，肌肉无力仍进展缓慢。加用静脉注射大剂量免疫球蛋白治疗后，肌肉无力明显改善，同时血清CK水平降低。在那些被认为是特发性高CK血症或遗传性肌肉疾病的患者中，确实存在潜在的免疫治疗有效组。我们建议在诊断时考虑此类病例，包括抗SRP抗体肌病，非侵入性MRI研究可能有助于区分免疫治疗有效组和遗传性肌肉疾病。
