Inclusion Criteria:

          1. Patients diagnosed as neurofibromatosis type 1 based on the clinical diagnostic
             criteria in guideline of Japanese Dermatological Association

          2. Patients participated in a Phase II/III investigator-initiated clinical trial for
             neurofibromatosis type I (OSD-001-004) who wish to continue treatment of the
             investigational drug

          3. At the time of enrollment, patients who are able to choose ten evaluable target
             lesions for efficacy (at least 5)..

          4. Patients who have evaluable skin neurofibromas at baseline.

          5. Males and females who are 3 years old or elder at the time of informed consent.

          6. Patients who (or whose guardian) give a written informed consent in understanding and
             willingness after having received enough explanation regarding the study
             participation.

          7. Patients whose use or continued use of the investigational drug is judged to be
             reasonable by the principal investigator or sub-investigator.

        Exclusion Criteria:

          1. Patients who occurred serious adverse effects, who discontinued the sudy due to
             adverse effects, or who discontinued the trial due to withdrew of their consent in the
             Phase II/III investigator-initiated study of neurofibromatosis type I (OSD-001-004)

          2. Patients with abnormal findings (e.g., pneumonia) in the results of chest x-ray at the
             time of screening

          3. Patients with creatinine clearance of less than 50 mL/min

          4. Patients with poorly controlled dyslipidemia (serum triglycerides >500 mg/dL or LDL
             cholesterol >190 mg/dL even with treatment)

          5. Patients who have complications such as infection, cardiac, hepatic, pulmonary, renal,
             or hematological diseases and malignant tumors that are considered unsuitable for
             participation in this trial.

          6. Patients with alcohol sensitivity or allergy to an ingredient of the study drug
             (Sirolimus)

          7. Female patients who are pregnant, may be pregnant, or are lactating

          8. Patients (including male patients with a fertile partner) who cannot consent to use
             adequate contraception from the date of consent to 12 weeks after the end of treatment

          9. Patients who participated in any other clinical trial or clinical study, other than
             the OSD-001-004 study, and have taken an investigational or investigational drug
             within 6 months prior to the date of the consent

         10. Patients who are participating in an observational study during this trial

         11. Patients who are considered by the investigator as unsuitable for participation in
             this trial