The aim of this study is to investigate pharmacokinetics and safety of N-acetylneuraminic acid in patients with Distal myopathy with rimmed vacuoles (DMRV) - hereditary inclusion body myopathy (hIBM). Dosages are 800mg single and three times a day and 800mg 3 times a day for 5 consecutive days. N-acetylneuraminic acid and N-glycolylneuraminic acid in serum and urine are measured before and after oral administration of N-acetylneuraminic acid.

Inclusion Criteria:

• Confirmed mutations in GNE gene
• No severe complications when informed consent is obtained
• More than 40 kg in weight before administration

Exclusion Criteria:

• Hepatic laboratory parameters (AST, ALT, γ-GTP) or Renal laboratory parameters (Cr, BUN) are greater than three times of upper limit of reference value
• Presence or history of clinically significant cardiovascular, pulmonary, hepatic, renal, hematological, metabolic, gastrointestinal, brain, psychiatric, neurologic disease
• Intake of supplement contains sialic acid, St. John's wort or grapefruit within 7 days
• Enrollment in another investigational study within 3 months
• More than 400 mL blood donation within 3 months
• Presence of alcohol or drug dependency
• Women who are pregnant , breast feeding or possible to be pregnant.
• Patients whom the investigator judges not to be appropriate for the subject