Clinical heterogeneity in Korean patients with nemaline myopathy

Abstract

Purpose: Nemaline myopathy (NM) is a clinical heterogeneous congenital myopathy characterized by the presence of subsarcolemmal or cytoplasmic rod-like structures that call nemaline bodies in the muscle fibers. The purpose of this study was to investigate the clinical diversity and pathological features of Korean patients with NM.

Materials and methods: Eight patients underwent analyses of clinical manifestations by a structured protocol. Diagnoses were established by a muscle biopsy.

Results: Two patients had the typical congenital type, which exhibited neonatal hypotonia and delayed motor milestone, and five patients had the childhood onset type, which exhibited mild gait disturbance as a first symptom. One patient had the adult onset type, which showed acute respiratory failure. Limb weakness was proximal-dominant occurred in six patients. Hyporeflexia was observed in most patients. Elongated faces and high arched palates and feet were also observed. On light microscopy, the nemaline bodies were observed in type 1 and 2 fibers. All patients showed type 1 predominance and atrophy. In the two cases in which ultrastructural studies were performed, typical nemaline rods and disorganized myofibrillar apparatus were detected.

Conclusion: In conclusion, the eight Korean patients in this study with NM shared common clinical expressions such as proximal limb weakness, reduced deep tendon reflex, and dysmorphic features. This study, however, showed that clinical heterogeneity ranged from typical congenital, mildly affected childhood to the adult onset form with acute respiratory failure. The pathological findings in this study were in accordance with those of other previous reports.

Keywords: Congenital structural myopathies; heterogeneity; nemaline myopathy.

Fig. 1

Pathologic findings of nemaline myopathy. (A and B) Hematoxylin and eosin staining (×50, ×100) reveals mild to moderate fiber size variation. Nemaline rods are not seen. (C and D) Numerous subsarcolemmal and cytoplasmic rods are apparent on a modified Gomori-trichrome stain (×100, ×200). (E) ATPase stain at pH 4.3 (×100) illustrates marked type 1 fiber predominance and hypotrophy. (F and G) NADH-TR stain (×200) shows selective type 1 fiber atrophy and modified Gomori-trichrome stain (×400) demonstrates selective rod formation in hypotrophic type 1 fibers. (H and I) Electron micrograph shows nemaline rods in cytoplasm and disorganized sarcomeric architecture with focal myofibrillar disarray.