Clinical and pathological features of patients with nemaline myopathy

Nemaline myopathy (NM) is a rare congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. This study aimed to summarize and analyze retrospectively the clinicopathological features of 28 patients with NM. Among the 28 patients, 15 were classified as of the typical congenital type, manifested as lower- or four-limb weakness as the first symptom and slowly progressive course. Six patients were classified as of childhood onset type, with lower-limb weakness and progressive course. Seven patients were classified as of the adult onset type, with rapidly progressive course and obvious muscle atrophy. Patient's 1, 16 and 23 had rapid clinical progression. On follow up, the three patients showed respiratory failure. Limb weakness in all patients was proximal‑dominant. Hypotonia was observed in most patients. High arched feet were also observed as dysmorfic features. In all patients, the creatine kinase (CK) level was normal or mildly elevated, and electromyography revealed myogenic changes. Nemaline bodies were observed under a light microscope in more than half of the patients' muscle fibers, and especially in type I fibers. All patients showed fiber type I predominance and atrophy. Modified Gömöri trichrome staining showed characteristic purple‑colored rods. Muscle electron microscopy revealed the presence of high electron‑dense nemaline bodies around the nucleus, and of a disorganized myofibrillar apparatus, with broken myofilaments and irregular myofibrils and Z lines. The 28 patients with NM shared a number of clinical features, such as proximal limb weakness, reduced deep tendon reflex and dysmorfic features. Differences were also observed between the three types of patients, with regards to course progression, disease severity and respiratory failure. In conclusion, patients with NM showed great clinical heterogeneity. The diagnosis of NM was mainly based on the muscle biopsy.