 The investigatoris will carefully select cartilage-hair hypoplasia patients unexposed to varicella VZV and immunize patients in a controlled manner with VZV vaccine. Patients will be selected on the basis of disease severity and the degree of immunodeficiency including CD4 T-cell counts. Any potential complication of VZV immunization, such as rash, will be discussed with the patientscaregivers beforehand and acyclovir will be used to treat any VZV related symptoms, consistent with the current practices. The investigators will verify the development of immune response to vaccination by testing for VZV antibodies and cell-mediated immunity. 