Abstract: Objective To explore the differential diagnosis of NF1 and vascular malformation using genetic testing. Methods A 10-year old boy’s right calf, with scattered erythema, has enlarged without definite boundaries for one year. More than 6 Café au lait, with diameter larger than 1.5 cm, scattered all over the trunk and limbs. CT: capillaries and superficial vein of right calf increased and enlarged, with an impression of tendency to venous malformations. In accordance with NF1 diagnosis criterion, it could not be diagnosed as NF1 without other typical symptom except caf é au lait. Then NF1 gene detection was performed. Results NF1 nonsense mutations was detected after DNA sequencing, c.C. 4006 C>T, p.Gln 1336 * (hybrid), supporting for NF1 diagnosis. Conclusion Genetic testing can be performed to help the diagnosis for the patients with atypical clinical manifestations.

Key words: Neurofibromatosis, Gene test, Vascular malformation