RESUMEN
Introduction: Lucio phenomenon is a rare type of reaction in untreated, diffusely infiltrative form of lepromatous leprosy type, characterised with ulcerative type of skin lesions. Case: A 29 year old Indonesian female, 7th months primigravida with a four-month history of painful scarlet spots that darken and ulcerate on both of her hands and legs. The patient was experiencing fever. The patient's eyebrows were lost and her earlobes were thickened 3 years ago. Slit-skin smear: BI 6þ,MI 7%. Histopathology: Lucio phenomenon. PCR detecting M. leprae DNA on skin lesion and amniotic fluid: positive; umbilical cord membrane and umbilical cord: negative. Anti-PGL-1 IgM and IgG: patient: 4,854 U/mL and 1,061 U/mL, respectively; 5 month-old baby: 5 U/mL and 1,724 U/mL, respectively; 1 year-old baby: 0 U/mL and 3 U/mL, respectively. Conclusion: Placenta is considered a protective barrier toward feto-maternal transmission of M. leprae. The baby had the passive antibody to M. leprae from the mother's blood transmitted through the umbilical cord as demonstrated by the presence of anti-PGL-1 IgG antibody.