Pinta is a chronic skin infection caused by treponema carateum.
Treponema carateum is quite similar to treponema pallidum in morphology and biological characteristics, with a width of 0.13 - 0.15μm and a length of 10 - 13μm, with various motion modes. The pathogen cannot grow in inanimate media, but can infect humans and chimpanzees.
The routes of transmission are skin to skin contact, small wounds caused by scratches or abrasions, and insect bites.
Treponema carateum enters the human body from the damaged skin and is disseminated to the whole body with lymph fluids or blood after local propagation, causing skin lesions and lymphadenopathy.
Signs and Symptoms
Pinta presents with only skin lesions, and other organs are not involved.
The incubation period is approximately 3 weeks (9 - 90 days). Pinta can be divided into primary pinta, secondary pinta, and tertiary pinta on the basis of clinical manifestations. However, in some epidemic areas, a small number of patients present with positive serological tests but no clinical manifestations of pinta, which can be considered latent pinta.
The initial skin lesion is a flat, red papule with little scales, predominantly on the exposed areas such as the extremities and trunk, especially the calves, gradually developing into a poorly demarcated, erythematous, scaly plaque in 3 months to 1 year. About 5 months after infection, there may be satellite papules near the plaque, which gradually expand and merge with the plaque, forming psoriasiform lesions, leaving hypopigmentation after regression. There are negative serological tests.
Secondary pinta and primary pinta are often concurrent, and it is difficult to recognize when secondary pinta starts exactly. In general, erythematous, scaly lesions occur in groups asymmetrically on the extremities and face 5 months to 1 year after infection, resembling the lesions of psoriasis, tinea corporis, eczema, syphilis, and leprosy. The lesions are initially bright red, developing into purplish red, scaly macules, which are termed pintids, leaving hypopigmentation after regression. The exposed areas often present with gray, yellow to brown pigmentation disorder, and there are both hyperpigmentation and hypopigmentation. The systemic lymph nodes are enlarged, indurated, and painless, resembling lymph nodes in secondary syphilis. The serological tests are positive in 60% of patients.
There are significant pigmentations on the skin 3 months to 10 years after pintids. There may be slowly expanding bluish grey spots with hypomelanotic macules on the face, wrists, and ankles, and there are mixed hyperpigmentation and hypopigmentation on the face, neck, limbs, trunk, oral mucosa, and nail beds. However, the color of hairs is not affected. The palms and soles can be mildly hyperkeratotic. The results of serological tests are almost always strong positive.
On the basis of epidemic areas and typical clinical presentations, the disease can be diagnosed. The serological tests are helpful for the diagnosis.
Adult patients can be treated with penicillin G benzathin 1,200,000 units intramuscularly once every 4 days for 16 days, while children with body weight less than 45kg can be treated with penicillin G benzathin 600,000 units intramuscularly.
Adults allergic to penicillin can be administered with azithromycin 30mg/kg, maximally 2g, orally in single dose or doxycycline 100mg orally twice a day for 14 days.
Several months after treatment, the serological tests can be negative, the bluish grey spots gradually subside, and hypomelanotic macules regress very slowly.