Pathology
The primary yaws lesion is histologically the same as the lesions of the generalized eruption of the second stage. In these lesions we fail to find the endothelial proliferations and perivascular round cell infiltrations so characteristic of syphilis. There is great thickening of the interpapillary pegs of the epidermis which dip down deeply into the corium. Areas are noted in the epithelium containing swollen degenerated epithelial cells, polymorphonuclears and granular débris. There is marked oedema in the corium with dilatation of the blood vessels and lymphatics.
There is less oedema of the corium in yaws than in a syphilitic condyloma thus accounting for the greater dryness of the former. The main point in the pathology of a yaws lesion is the predominating involvement of the epidermis and the comparatively slight change in the corium.
In a Levaditi-stained specimen the spirochaetes are found in the epidermal layers instead of in the corium as with syphilis.
The visceral organs and central nervous system are not affected although Harper has reported cases of tabes and general paresis in Fijians following yaws. He excludes syphilis.
Symptomatology
It is usual to consider the clinical course of yaws as exhibiting two stages, the primary one, which comes on from 2 to 5 weeks after introduction of the virus and is characterized by a papular initial lesion, which later shows the fungoid appearance of a typical yaws tubercle, and the secondary stage in which yaws lesions similar to the initial one develop as a generalized eruption.
Some authorities recognize a tertiary stage in which gumma-like nodules, with subsequent ulceration, appear. There is much evidence to indicate that a destructive ulceration of the nasopharyngeal region, in natives of Guam, is a tertiary manifestation of yaws.
