A66.4

Clinical Causes: Infection with *Treponema pallidum pertenue*, a bacterium transmitted through direct skin contact with infectious lesions. Poor sanitation and living conditions that facilitate close contact and hinder hygiene practices. Environmental factors such as warm, humid climates that support bacterial survival and transmission. Lack of access to medical care, which delays diagnosis and treatment, allowing the disease to progress.

Key Symptoms: Initial skin lesions that are painless, rough, and ulcerative, typically appearing on the limbs, face, or hands. Progression to nodular, indurated lesions called gummata, which are soft, tumor-like swellings that can develop into ulcers. Ulcerative sores with raised, inflamed edges that may ooze or crust. Chronic skin ulcerations, especially in the late stages, leading to disfigurement if untreated. Potential involvement of bones causing painless periostitis, bone destruction, or deformities. Lymphadenopathy — swelling of the lymph nodes near the infection sites.

Diagnosis Path: Serologic tests such as non-treponemal (e.g., VDRL, RPR) and treponemal (e.g., FTA-ABS, TPPA) assays. Microscopic examination of lesion exudates or tissue biopsies using darkfield microscopy or silver stains to identify *Treponema pallidum pertenue*. Histopathological examination revealing granulomatous inflammation and gummatous tissue changes.

Treatment Protocols: Benzathine penicillin G injections are considered the first-line treatment for yaws. For patients allergic to penicillin, alternatives such as doxycycline or azithromycin may be used under medical supervision. Supportive care to manage symptoms, prevent secondary infections, and promote healing of ulcers. Addressing environmental and social factors to prevent reinfection, such as improving hygiene and reducing close contact situations.