[Sporadic late-onset nemaline myopathy with monoclonal gammopathy of undetermined significance mimicking POEMS syndrome].

A 40-year-old female presented with a skin rash, hepatosplenomegaly, hypothyroidism, IgG-λ monoclonal gammopathy, slightly elevated serum VEGF levels, and >1-year history of weakness in the posterior cervical muscles. Based on these symptoms and her clinical course, she was suspected of having POEMS syndrome. However, because there was no sign of peripheral neuropathy (PN), the criteria for the diagnosis of POEMS syndrome were not met. Consequently, she continued follow-up and was under close observation as an outpatient. She complained of slowly progressive dyspnea that was identified as type 2 respiratory failure requiring non-invasive positive pressure ventilation. She received systemic chemotherapy, including thalidomide and dexamethasone, as the respiratory failure was predominantly a result of POEMS-associated PN. Although the skin eruptions improved upon treatment, respiratory failure gradually worsened, and she required mechanical ventilation. The patient was suspected of having sporadic late-onset nemaline myopathy with monoclonal gammopathy of undetermined significance (SLONM-MGUS), because of resistant to chemotherapy and second opinion suggestion. A thigh muscle biopsy revealed the presence of nemaline rods and led to the definitive diagnosis of SLONM-MGUS. Unfortunately, she was unable to receive autologous stem cell transplantation, and finally died because of progressive respiratory failure. SLONM-MGUS is an extremely rare disease but should be considered as a critical, monoclonal-protein related condition.