G.O.28: Sporadic late onset nemaline myopathy with MGUS: long term follow-up after melphalan and autologous stem cell transplantation

Abstract

Sporadic late-onset nemaline myopathy (SLONM) is a rare, late-onset myopathy that progresses subacutely. Limb-girdle and axial weakness and atrophy predominate the clinical picture. Distal weakness, head drop, respiratory insufficiency, and dysphagia can also occur. Recognition of nemaline rods on trichrome staining in the biopsy is crucial. This can be confirmed by immunohistochemical staining of the muscle biopsy with alpha-actinin antibodies and by electron microscopy. SLONM is in a significant proportion (50 %) of cases associated with a monoclonal gammopathy of unknown significance (MGUS), a combination which portends an unfavorable outcome: the majority (70 %) of these patients die within 1–5 years of respiratory failure. Treatment with high dose melphalan (HDM) followed by autologous stem cell transplantation (SCT) has proven to be effective in individual cases. We performed a prospective, observational case series (n = 8) on the long-term (nine months–eight years) treatment effect of HDM followed by autologous SCT. Seven patients showed a partial or complete hematological response, and six a lasting moderate-good clinical response. Two patients had a relapse and underwent a second cycle of HDM–SCT. One patient showed no response and died. This case series thus shows the positive effect of HDM and SCT in this rare disorder (Class IV). Factors which may portend an unfavorable outcome are a long disease course before the hematological treatment and a poor hematological response. Age at onset, level and kind of M-protein (kappa vs. lambda), and severity of muscle weakness were not associated with a specific outcome.