Syphilis – Part 1- Diagnosis, VDRL, FTA-ABS, TPHA, RPR (Treponema Pallidum)

Sample

• The serum of the patient is needed.

Indication

• For the diagnose of syphilis.

Pathophysiology

1. The disease syphilis was reported in the medical literature as early as 1495.
   1. In the treatment of syphilis. heavy metals, such as arsenic, were replaced by penicillin 1940.
   2. Treponema pallidum is a member of the order Spirochaetales and family Treponemataceae.
2. Spirochetes are a gram-negative organism and look like corkscrews.
   1. These are fine, spiral 8 to 24 coils organism. These are approximately 6 to 15 µ mm long.
   2. These bacteria can move in a spinning fashion called axial filaments.
   3. These bacteria replicate by transverse fission.
   4. This organism can not grow in ordinary media.
   5. These have a gram-negative cell membrane.
   6. These are too small to see under the light microscope.
      1. So a special procedure is used to see these organisms like dark-field, immunofluorescence, and silver stain.
      2. Also, serological tests can help to diagnose syphilis.
3. Syphilis is a chronic venereal disease.
4. This was discovered in epidemic form in the 16th century in Europe.
5. The first diagnostic blood test for syphilis was introduced by Wassermann in 1906.
6. Afroamericans are infected 30 times more than white Americans.
7. Mode of spread:
   1. Syphilis is caused by Spirochaete Treponema Pallidum and its natural host is humans.
   2. The most common source of infection is a cutaneous or mucosal lesion in the primary or secondary stage of the disease.
      1. During sexual acts, the organism enters the body through minute abrasion of the skin or mucous membranes.
      2. Once it enters the body, the spirochetes immediately being disseminated throughout the body.
   3. In congenital syphilis, it spreads across the placenta to the fetus.

8. The incubation period is 2 to 4 weeks.
9. Syphilis can spread through:
   1. sexual contact
   2. Congenital
   3. Direct contact with the lesion.

Treponema associated diseases in human:

1. T. Pallidum = Syphilis
2. T. pallidum variant = Bejel
3. T. carateum = Pinta
4. T. pertenue = Yaws

Syphilis has four clinical stages :

1. Incubation period: This is 2 to 4 weeks.
2. The primary stage:
   1. This is characterized by the presence of the chance at the primary site of inoculation.
   2. In the male is at the penis and in the female are multiple presents on the vagina or the cervix.
   3. It has a firm and usually painless ulcer called Chancre.
   4. 

      Primary Chancre on Penis

   5.  Enlarged lymph nodes may be seen and are painless.
      
   6. This heals spontaneously in 3 to 8 weeks.
   7. The lesion is positive for the spirochetes.
   8. Serological tests for syphilis are often negative in the early phase of the disease so advise darkfield microscopy or a direct fluorescent antibody test.
3. The secondary stage:
   1. 25% of untreated cases from the primary chancre goes into the secondary stage.
   2. The Patient may develop this stage after roughly 2 months of the chancre (or 6 to 8 weeks).
   3. 6 to 8 weeks later infection becomes generalized, this is the bacteremia stage.
   4. This is characterized by the appearance of the systemic lesions on:
      1. Mucous membranes, large mucous membrane lesions may be seen in the oral cavity.
      2. There are widespread rashes of the skin.
         1. These rashes are small red flat lesions distributed over the body.
      3. Cutaneous surfaces, warts like lesion called Condylomata are seen. Usually seen in the moist and warm sites like the perianal area, vulva, and the scrotum.
      4. Any organ may be involved including CNS, eyes, kidneys, and bones.
   5. This is a highly infectious stage and contains many organisms (treponemes).
   6. There is generalized lymphadenopathy in 50% of the cases.
   7. Other rare complications are arthritis, hepatitis, glomerulonephritis, periostitis, and sometime iridocyclitis and chorioretinitis.
   8. These mucocutaneous lesions are highly infectious.
4. Latent syphilis: The disease is dormant for many years. The symptoms of the second stage have resolved.
   1. But serological tests are positive.
   2. 25% or more will have a relapse and develop the infectious lesion of the skin like secondary syphilis.
      1. After 4 years, there are generally no more relapses, and this disease may be noninfectious except the pregnant mothers.
   3. This ultimately develops into cardiovascular or neurosyphilis.
   4. Roughly 1/3 cases progress into the tertiary stage.
5. late syphilis: This occurs after 10 o 20 years of the primary lesion.
   1. There are two main types:
      1. Cardiovascular involvement in the form of Aortitis and aneurysm.
      2. Neurosyphilis which may be:
         1. General paralysis with dementia, tremors, and spastic paralysis.
         2. Tabes dorsalis with ataxic gate, trophic changes in joints in the form of Charcot’s joints.
         3. There may be optic atrophy.
         4. Meningovascular syphilis gives a headache, cranial nerves palsies, and Argyll- Robertson pupil (pupillary loss of reaction to light).
6. Tertiary stage:
   1. This stage appears 3 to 10 years after the primary lesion (another source says 6 to 40 years takes to develop the tertiary stage).
   2. This is also called late syphilis and is a noninfectious stage.
   3. This is characterized by granulomatous skin lesion called gummas, may occur on mucous membrane, subcutaneous tissue bone, and viscera.
   4. The main presentation is:
      1. Gumma formation.
         1. The gummatous lesion appears after 3 to 10 years of the primary lesion in about 15% of the untreated cases.
         2. These are a granulomatous lesion.
         3. These are noninfectious lesions mainly found in the skin and the bone.
      2. Cardiovascular involvement.
         1. These are seen after at least 10 years of the primary infection in 10% of the untreated cases.
         2. There is an aneurysm in the aorta (ascending part), or aortic arch.
      3. Neurosyphilis.
         1. This disease is seen in roughly 8% of the untreated cases.
         2. Neurosyphilis presentation is as follows:
            1. Asymptomatic when the patients are normally looking but the CSF is serologically positive.
            2. Subacute meningitis where the patients have a fever, stiff neck, and headache.
               1. CSF examination shows:
                  1. Increased proteins.
                  2. Low glucose level.
                  3. Increased number of lymphocytes.
                  4. Positive tests for syphilis.
            3. Meningovascular syphilis where there is damage to the blood vessels of the brain and meninges.
               1. There are cerebrovascular occlusion and infarction of the tissue in the brain, meninges, and spinal cord.
         3. Tabes dorsalis affects the spinal cord.
            1. In this case, there is the involvement of the posterior column and dorsal roots.
7. Late or quaternary stage: 10 to 20 years after primary syphilis, there are two main clinical sequences:
   1. Neurosyphilis may present as follows:
      1. General paralysis of insane with dementia, tremor, and spastic paralysis.
      2. Tabes dorsalis with characteristic features of ataxic gait, atrophic changes in joints, Charcot’s joints, and there may be optic atrophy.
      3. Meningovascular syphilis with a headache, cranial nerve palsies, and papillary loss of reaction to light (Argyll-Robertson pupil).

Clinical stage	Clinical presentation
Primary stage	Chancre, painless
Secondary stage	1. Skin involvement with the presence of rashes 2. Involvement of CNS, bones, eyes, kidneys, arthritis 3. Condylomata latum
Latent stage	25% may relapse and again goes into the secondary stage
Tertiary stage	1. Neurosyphilis 2. Involvement of the cardiovascular system 3. Gumma of the skin and bone

8. Congenital syphilis:
   1. Bacteria can enter into fetal circulation at any time from the placenta during pregnancy. So these bacteria can cross the placental barrier.
   2. The chances are more when the mother is in the primary or secondary stage to infect the fetus.
   3. In the absence of the treatment, roughly 40% of the fetus will die in utero around the 4th month of the pregnancy.
   4. The manifestation of the congenital syphilis are:
      1. Stillbirth.
      2. Infantile syphilis.
      3. Hepatosplenomegaly, and bone abnormalities.
      4. There are pancreatic fibrosis and pneumonitis.
      5. The lungs may be firm and pale.
      6. Tissues are positive for the spirochetes.
   5. Congenital syphilis was clinically seen as:
      1. Latent infection when there are no symptoms but infants are serologically positive.
      2. The early-stage appears after the end of the second year.
         1. Most infants are healthy at birth and symptoms appear in the first few weeks.
         2. There are generalized skin rashes, nasal deformity. hepatitis, meningitis, anemia, and bone lesions.
      3. Late syphilis manifestations appear in the first few weeks of life.
         1. They may not be able to thrive.
         2. There is bone sclerosis.
         3. Joint effusion and arthritis.
         4. Interstitial keratitis.
         5. Juvenile general paralysis of the insane and tabes.
         6. Deafness.
         7. Notching of the incisor teeth.

The principle of the Various test

1. Tests depended upon T.pallidum demonstration by:
   1. Darkfield direct microscopy: The Patient lesion is abraded and fluid is taken which is seen immediately directly under the dark field microscope. It has a sensitivity of 80 %.
   2. Fluorescent microscopy: Where again the sample is taken directly from the lesion and treated with fluorescently labeled antibody and seen under the fluorescent microscope.
2. Non-treponemal tests measure antibodies against the cardiolipin.
   1. These serologic tests are:
      1. Venereal disease research laboratory (VDRL).
      2. Rapid plasma reagin (RPR).
         1. These tests become start positive after 1 to 2 weeks of infection and are positive by 4 to 6 weeks.
         2. Titer starts falling after the successful treatment.
         3. These nontreponemal tests are negative in the early stage of the disease, then the darkfield examination will be positive.
         4. 

            Principle of VDRL test

3. ELIZA
   1. Treponemal serologic test detect antibody to the antigen and these are:
      1. Fluorescent treponemal antibody absorption (FTA-ABS).
      2. Microhemagglutination treponema Pallidum (MHA-TP).
4. TPHA (Treponema pallidum hemagglutination assay) is a treponemal antigen serologic test for syphilis.
   1. Tanned sheep red blood cells coated with antigen from Nichol’s strain of Treponema pallidum are treated with the serum of the patient.
   2. Sensitivity and specificity are just like the FTA-ABS test.
   3. This test is not useful for individuals who have had syphilis in the past.
5. PCR is recommended for neurosyphilis.

Disease	dark field	RPR	VDRL	FTA-Abs	TP-PA	AIA	TPHA
Primary syphilis  10 to 90 days	Positive	positive	positive				negative
Late primary		positive	positive	positive			positive
Latent syphilis	positive/negative	positive	positive	positive			positive
Secondary syphilis 6 weeks to 6 months		positive	positive	positive	positive	positive
Tertiary  syphilis 10 to 30 years		positive/negative	positive/ negative	positive	positive	positive
Treated syphilis	negative			positive			positive
Congenital syphilis	positive			positive			positive

• TP-PA = Treponema pallidum particle agglutination assay.
• FTA- Abs = Fluorescent treponemal antibody absorption.
• TPHA = Treponema pallidum haemagglutination  test.
• RPR = Rapid plasma reagin.
• AIA = Automated immunoassay for syphilis antibody.
• VDRL = Venereal disease research laboratory test.

For the diagnosis of neurosyphilis advice:

1. VDRL.
2. Wasserman test.
3. FTA.
4. When these tests are positive on CSF in the latent syphilis are diagnostic for the diagnosis of neurosyphilis.
5. FTA is more specific for the diagnosis.

Treatment

• The drug of choice is penicillin.

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