CAUSATIVE ORGANISM
Treponema pallidum is the causative organism for Syphilis. Syphilis affects the skin and mucous membrane of the external genitalia, and sometimes the mouth.
It is gram-negative bacterium.
Treponema pallidum is an obligate bacterium, meaning they can’t survive outside a human body.
They belong to a group of bacteria called spirochetes, which are long and thin, and contain endoflagella that give them a spiral/corkscrew shape.
The endoflagella provides characteristic spinning motion to spirochetes.
Direct contact with a skin lesion on an infected person fluid which is rich in spirochetes.
Congenital Syphilis- When a pregnant mother has syphilis and Treponema pallidum infects a baby either in the uterus or while the baby exits through the vagina at birth.
ACQUIRED SYPHILIS
In acquired syphilis, there are three stages to the infection.
1. PRIMARY SYPHILIS (early localized stage)
The first stage is called primary syphilis or the early localized stage
It usually starts 1 to 3 weeks after the T. pallidum lands on the skin or mucous membrane.
During this stage, the spirochetes destroy the soft tissue and skin wherever they enter the body, and result in the formation of ulcers called syphilitic chancres.
A syphilitic chancre is painless.
These chancres have a hard base, raised borders, and are usually covered by a fluid rich in spirochetes, and this can spread to other parts of the body as well as to other individuals.
In individuals who acquire syphilis through sexual contact, the primary chancre develops around the external genitalia.
However, for individuals that acquire syphilis by physically touching a lesion or in some other way, the primary chancre might appear on the hands or some other part of the body.
Syphilitic chancres typically heal on their own over a few months, but during that time, some spirochetes go to nearby lymph nodes where they cause lymphadenopathy, and then they get into the lymph and finally into the bloodstream.
If syphilis is acquired through blood transfusion, then there may not be any early localized stage and no primary chancre.
2. SECONDARY SYPHILIS
The second stage is secondary syphilis, or the dissemination stage.
It occurs about 6 to 12 weeks after the infection.
During this stage, spirochetes enter the bloodstream, which is called spirochetemia, and this causes generalized lymphadenopathy, which is when spirochetes can be found in lymph nodes throughout the body.
The spirochetes attach to and infect endothelial cells in small capillaries near the skin. This causes a non-itchy maculopapular rash, which are small bumps that are either flat or raised.
The rash starts on the trunk and spreads out to the arms and legs and eventually to the palms, soles, genitalia, and other mucous membranes.
These rashes can sometimes contain pus, or they can be papulosquamous, which is when they’re scaly and hard.
In addition, there can be something called ‘condyloma lata’, which are smooth, white, painless, wart-like lesions, and they appear on moist areas like genitals, around anal region, and the armpits.
These various rashes can erupt all over the body, and the lesions filled with spirochetes make secondary syphilis the most infectious stage.
The rashes from secondary syphilis usually resolve within a few weeks to months.
3. LATENT SYPHILIS
Then after secondary syphilis, is a latent phase, called latent syphilis.
The disease enters a dormant or asymptomatic phase.
During this phase, the spirochetes can mostly be found in the tiny capillaries of various body organs and tissues.
Latent syphilis can be further divided into an early phase and a late phase.
Early Phase
Occurs within a year of infection.
During this time the spirochetes can re-enter the blood – so this means that during early latent syphilis they can still be found circulating in large numbers in the blood, causing symptoms of secondary syphilis.
Late Phase
Generally, occurs after a year.
The spirochetes generally stay within the tiny capillaries of various body organs and tissues.
few spirochetes found in the capillaries of tissues and organs elicit a severe immune response. It causes tremendous damage to the cells. This triggers tertiary syphilis.
TERTIARY SYPHILIS
There is a type IV hypersensitivity reaction, – immune response is mainly led by the T cells.
T. pallidum has three main antigens-
→ GROUP SPECIFIC ANTIGEN, present in all treponemas
→SPECIES-SPECIFIC ANTIGEN, specific to T. pallidum
→CARDIOLIPIN, a lipid antigen is present within the spirochetes as well as the cells in our body.
Plasma cells produce antibodies against these antigens.
GUMMA- In some cases, the immune cells start to huddle around and form a granulomatous lesion called a GUMMA, and this has different types of immune cells that get surrounded by an outermost layer of fibroblasts.
Often, there aren’t any spirochetes at all in these lesions.
The tissue at the centre of the gumma odes not receive any oxygen without oxygen and this leads to coagulative necrosis.
In tertiary syphilis various organs get damaged, like-
The heart and blood vessels- cardiovascular syphilis
The brain and spinal cord- neurosyphilis
The liver, joints, and testes
CARDIOVASCULAR SYPHILIS
Endarteritis- Inflammation of the tiny arterioles called vasa vasorum, which supply blood to large arteries like the aorta.
Due to this, parts of the aorta get damaged, resulting in aortitis (inflammation of the aorta).
NEUROSYPHILIS
POSTERIOR PART OF SPINAL CORD
The spirochetes aggregate in the capillaries supplying the posterior or back part of the spinal cord. This causes tabes dorsalis, that is wasting or loss of the back of the spinal cord.
The protective sheath which covers the nerves running along the back of the spinal cord is damaged, and this results in loss of vibration sensation, and loss of proprioception, (the sense of position of the joints and other body parts, like the hands and the foot.)
ANTERIOR OF SPINAL CORD
Invasion of spirochetes in the capillaries supplying the anterior or front of the spinal cord causes loss of sensation, and weakness, or sometimes even paralysis, mostly in the legs.
BRAIN
If spirochetes get into the capillaries serving the brain then they cause slurred speech, altered behavior, memory loss, difficulty coordinating muscle movements, and even paralysis.
Syphilis can even affect the eye, causing an Argyll Robertson pupil, which is when the pupil loses its light reflex, but it does still have its accommodation reflex, which means that the pupil constricts when there’s a nearby object, it just doesn’t do anything when it’s too light.
CONGENITAL SYPHILIS
In congenital syphilis, the spirochetes can infect the baby either via the placenta or during childbirth in the birth canal.
In early disease–
In the first two years
Baby being still-born, or dying within the womb or
Features like
A maculopapular rash of the palms and soles of the feet
Snuffles, which is when the nose is blocked by increased secretions, which contain spirochetes.
Babies may also have organ damage to the liver and spleen causing hepatosplenomegaly and damage to the eyes- optic neuritis.
In late disease-
After a child is two years old
Saddle nose- bony destruction of the nose,
Tibia gets bent
Hutchinson teeth- the teeth develop little notches
Hearing loss.
