All 3 reported cases of NM with chylothorax were male with severe congenital presentation of myopathy and de novo dominant mutation in ACTA1. Among these three cases of NM with chylothorax, none survived more than 9 weeks indicating a poor prognosis in this group and suggesting that this represents a poor prognostic sign. The gene discussed is ACTA1; the disease is nemaline myopathy.