Sporadic late-onset nemaline myopathy (SLONM) is distinct from congenital nemaline myopathies, which are associated with genetic abnormalities. There are many cases of SLONM with M-proteinemia, but treatment response and life expectancy are poor. Several studies have reported that patients with M protein-positive SLONM treated with high-dose melphalan combined with autologous hematopoietic stem cell transplantation (HDM-ASCT) presented good long-term outcomes. These reports suggest that early diagnosis is important, however, it is often time-consuming to diagnose or may be misdiagnosed as other conditions. In recent years, knowledge of the pathology of SLONM and nemaline myopathies has gradually increased. This article provides an overview of SLONM, focusing on the characteristic clinical and myopathological findings.