<prompt> Incubation period of syphilis is9-90 days2-6 weeks1-3 weeks5-7 days  <response>: Ans. a 9-90 days. Ref. Harrison, Medicine, 18thCh. 169; Table 170-1SYPHILIS L Pallidum enters foetal circulation after 20th week of gestation with disappearance of cytotrophoblast in villi Kerala-2001. Basic pathology is obliterative endarteritis, in congenital syphilis. Placenta becomes bulky and spirochaete can hardly be found in placenta. Spirochaete can however be detected from maculopapular rash in baby. Irrespective of the serology, treatment should be repeated in subsequent pregnancies. Incubation period of syphilis is 9-90 days In blood transfusion and in congenital syphilis, no chancre occurs. Dark ground microscopic examination is useful but negative results do not exclude diagnosis of syphilis. Diagnosis by microscopy is applicable in primary and secondary stages and congenital syphilis. Wet film prepared with exudates is seen under dark ground microscope. T. pallidum shows slow movement with slender spiral structure However, serology remains the best diagnostic test for syphilis. Serological tests for syphilis are:- Tests for antibodies reacting with cardiolipin antigen Non-specific reagin test, standard tests for syphilis VDRL is std test for syphilis- Tests for antibodies reacting with group specific treponemal antigens.- Tests for specific antibodies to pathologic T. pallidum.Comparison of the Treponemes and Associated DiseasesFeatureVenereal SyphilisYawsEndemic SyphilisPintaOrganismT. pallidum subsp. pallidumT. pallidum subsp. pertenueT. pallidum subsp. endemicumT. carateumModes of transmissionSexual, transplacentalSkin-to-skinHousehold contacts: mouth-to-mouth or via shared drinking eating utensilsSkin-to-skinUsual age of acquisitionAdulthood or in uteroEarly childhoodEarly childhoodLate childhoodPrimary lesionCutaneous ulcer chancrePapilloma, often ulcerativeRarely seenNonulcerating papule with satellites, pruriticLocationGenital, oral, analExtremitiesOralExtremities, faceSecondary lesionsMucocutaneous lesions; condylomata lataCutaneous papul osquamous lesions; osteoperiostitisFlorid mucocutaneous lesions mucous patch, split papule, condyloma latum; osteoperiostitisPintides, pigmented, pruriticInfectious relapses25CommonUnknownNoneLate complicationsGummas, cardiovascular and CNS involve- mentaDestructive gummas of skin, bone, cartilageDestructive gummas of skin, bone, cartilageNondestructive, dyschromic, achromic macules 