Skin ulcus molle is the old Latin name for chancroid, also called soft chancre. It is a bacterial sexually transmitted infection (STI) that causes painful, soft sores (ulcers) on the skin of the genital or nearby areas. The infection is caused by a germ (bacteria) named Haemophilus ducreyi, which enters through tiny cuts in the skin during sexual contact. DermNet®+1
The ulcer is called “soft” because its edge is soft when a doctor feels it, unlike the “hard” painless ulcer of syphilis. The sore usually starts as a small red bump, then becomes a pus-filled spot, and finally breaks down into an open ulcer. These ulcers are very painful and may be single or many. Nearby groin lymph nodes can also swell and may form buboes (large tender lumps). IUSTI+1
Chancroid is more common in areas with limited access to sexual health services, in people with multiple sexual partners, and in places where other STIs such as HIV are also common. It is now rare in many high-income countries but still occurs in some low- and middle-income countries. NCBI+1
Sometimes Haemophilus ducreyi can also cause non-genital skin ulcers, especially on the legs of children in some tropical islands, without sexual contact. However, when doctors say ulcus molle or soft chancre, they usually mean the genital STI form. DermNet®+1
Other names of skin ulcus molle
1. Chancroid
“Chancroid” is the most common modern medical name. It comes from the word “chancre,” which means ulcer or sore. Chancroid is used in current textbooks, guidelines, and patient information, and it always refers to this specific STI caused by Haemophilus ducreyi. Wikipedia+1
2. Soft chancre
“Soft chancre” is a descriptive name. It reminds clinicians that this ulcer is soft and painful, unlike the hard, painless chancre of primary syphilis. This difference helps doctors when they check genital ulcers and think about which disease is more likely. PubMed+1
3. Ulcus molle
“Ulcus molle” is the traditional Latin term and means “soft ulcer.” It is still used in many older books and some modern articles. When you see “ulcus molle,” it almost always means chancroid, not other types of ulcers. PubMed+1
4. Ducreyan chancre or Ducrey’s chancre
Some authors call the ulcer Ducreyan chancre to honor Ducrey, the doctor who first described the bacteria Haemophilus ducreyi. This name is less common now but may appear in older publications or exams. ACP Journals+1
5. Haemophilus ducreyi genital ulcer disease
In research reports and guidelines, chancroid is sometimes called Haemophilus ducreyi genital ulcer disease. This phrase reminds us that the ulcer is part of the broader group of genital ulcer diseases (GUD), which also includes syphilis and genital herpes. NCBI+1
6. Chancroidal ulcer
Some dermatology sources use the term chancroidal ulcer to describe the typical painful ulcer caused by H. ducreyi. This helps separate it from ulcers caused by other germs or non-infectious skin conditions. DermNet®+1
Types of skin ulcus molle
1. Classic genital chancroid
This is the most common type. The ulcers are on the penis, vulva, vagina, cervix, or around the anus, depending on the type of sexual contact. The sores are painful, soft, and have ragged edges and a dirty-looking base. Groin lymph nodes often swell and may form buboes. DermNet®+1
2. Extragenital chancroid
In some cases, ulcers can appear on non-genital skin, such as the thigh, lower abdomen, or fingers, often due to accidental transfer of infected fluid to broken skin. This is still the same infection with H. ducreyi, but the location is outside the usual genital area. Wikipedia+1
3. Mixed-infection chancroid (with syphilis or herpes)
About 10% of people with chancroid also have syphilis or HIV, and co-infection with genital herpes (HSV) can also happen. In mixed infections, the ulcers may not look typical, and there may be both soft painful areas and other types of sores. This makes diagnosis harder and needs careful testing for multiple STIs. NCBI+1
4. HIV-associated chancroid
In people with HIV, chancroid may present with larger, deeper, or slower-healing ulcers, sometimes with more extensive tissue damage. The infection can also increase the risk of HIV transmission and acquisition because the open ulcers give the virus an easy entry point. NCBI+1
5. Non-sexually transmitted cutaneous H. ducreyi ulcers
In certain tropical regions, especially in South Pacific islands, H. ducreyi can cause non-genital skin ulcers in children and young adults, usually on the legs. These are not sexually transmitted but are due to the same bacteria. They are often grouped under “tropical skin ulcers” and may be confused with yaws or other infections. DermNet®+1
6. Chronic or neglected chancroid
If chancroid is not treated, ulcers can become chronic, with extensive destruction of nearby skin and tissue. Large buboes may break open and leave draining sinuses. This type is now less common where antibiotics and STI clinics are available, but it is still described in older literature and in resource-limited settings. IUSTI+1
Causes and risk factors of skin ulcus molle
Remember: the direct cause is always infection with Haemophilus ducreyi. The items below describe conditions and behaviors that allow this germ to spread more easily.
1. Infection with Haemophilus ducreyi
The main cause is direct infection by Haemophilus ducreyi, a small, fragile, gram-negative bacteria. It enters through tiny breaks in the skin during sexual contact, multiplies locally, and leads to tissue destruction and ulcer formation. Wikipedia+1
2. Unprotected vaginal, anal, or oral sex
Not using condoms or barriers allows infected fluid from one partner to touch the skin or mucosa of the other partner. When there are micro-tears in the skin, the bacteria can enter and start the infection, especially during rough or prolonged intercourse. World Health Organization+1
3. Multiple sexual partners
Having many sexual partners increases the chance of meeting someone who already carries H. ducreyi or other STIs. This pattern is strongly linked to outbreaks of chancroid in high-risk networks, including sex workers and their clients. NCBI+1
4. Sex with partners who have genital ulcers
Direct contact with a visible sore containing H. ducreyi greatly increases the risk. The ulcer fluid has a high number of bacteria, so even brief contact may be enough to transmit the infection. CDC+1
5. Micro-trauma to genital or nearby skin
Small, often invisible tears in the genital skin occur during intercourse or from friction. These micro-injuries give the bacteria easy access to deeper skin layers, where they can survive and cause ulcers. Wikipedia+1
6. Poor access to sexual health services
In communities with limited STI clinics, testing, or treatment, chancroid can spread silently. People may delay seeking care or use ineffective medicines, so the infection continues in the population. World Health Organization+1
7. Inconsistent or incorrect condom use
Using condoms only sometimes, putting them on late, or removing them early leaves times when skin contact still occurs. Also, areas not covered by the condom (like the base of the penis or surrounding skin) can still touch ulcers and spread the infection. CDC+1
8. Co-existing STIs (such as HIV, syphilis, herpes)
Other STIs can cause inflammation, ulcers, or immune changes. These changes may make it easier for H. ducreyi to enter and multiply. Chancroid itself also increases HIV transmission risk by breaking the skin barrier. NCBI+1
9. Low socioeconomic status and crowded living
Poverty, overcrowding, and limited education are linked with higher rates of many STIs, including chancroid. These factors can limit access to condoms, health information, and timely medical care. World Health Organization+1
10. Sex work without adequate protection
Sex workers and their clients are often described as core groups for chancroid transmission. High partner turnover and inconsistent condom use can maintain the bacteria in these networks. NCBI+1
11. Previous history of genital ulcers
People who have had genital ulcers in the past may have scarred or fragile skin, which can tear more easily and may again become infected if exposed to H. ducreyi. DermNet®+1
12. Poor genital hygiene
Not washing the genital area, especially after sex, may allow bacteria to stay longer on the skin surface and in moist areas, increasing the chance of infection. Hygiene alone does not cause the disease but contributes as a risk factor. DermNet®+1
13. Lack of STI education and awareness
If people do not know that painful genital sores may be an STI and need treatment, they might delay seeking care. They may continue sexual activity while infectious, which spreads the bacteria to others. World Health Organization+1
14. Alcohol and drug use during sex
Alcohol or drugs can lower self-control and judgment. People may forget to use condoms or choose partners more impulsively, raising the risk of exposure to H. ducreyi and other STIs. World Health Organization+1
15. Male circumcision status and local skin conditions
Some studies suggest that uncircumcised men have more moist folds where bacteria can stay and where tiny ulcers or tears may form. However, this relationship is complex and may differ by setting. Wikipedia+1
16. Use of shared sex toys without proper cleaning
If sex toys with contaminated fluids are shared between partners and are not cleaned or covered with new condoms between uses, bacteria may move from one person to another. CDC+1
17. Travel to high-prevalence regions
Travelers who have unprotected sex in areas where chancroid is more common may become infected and later bring the germ back to their home country, even if chancroid is rare there. NCBI+1
18. Non-sexual skin contact with infectious material
Although rare, accidental infection can occur if ulcer fluid touches broken skin on the hand (for example, in health workers or caregivers) and is not cleaned quickly. Wikipedia+1
19. Tropical climate and insect bites in cutaneous forms
In the non-genital, non-sexually transmitted forms in tropical islands, frequent skin trauma from insect bites or injuries may allow H. ducreyi from the environment or other skin sites to enter and cause ulcers on the legs. DermNet®+1
20. Delayed or incomplete treatment of early infection
If early chancroid is not treated with effective antibiotics, the bacteria continue to multiply. Untreated people remain infectious and can spread the germ to others, sustaining the disease in the community. CDC+1
Symptoms and signs of skin ulcus molle
1. Painful genital or nearby skin ulcer
The main symptom is one or more painful ulcers on the genitals or nearby skin. The ulcer usually starts as a small, red bump and within a few days breaks down into an open sore that hurts a lot when touched or rubbed. MSD Manuals+1
2. Soft, ragged, undermined ulcer edges
The edge of the ulcer is typically soft and may look ragged or “eaten away.” When a doctor presses on it, it does not feel firm. This helps distinguish it from the firm, hard edge of a syphilis chancre. IUSTI+1
3. Dirty-looking, yellow-gray ulcer base
The base of the sore is often covered with a yellow or gray layer of pus and dead tissue. It may bleed easily when scraped or rubbed. This gives the ulcer a “dirty” appearance. Wikipedia+1
4. Strong tenderness and touch pain
People with chancroid often report intense pain, especially when clothes rub over the sore or during urination or sexual activity. The pain is different from the usual mild discomfort of some other STIs. MSD Manuals+1
5. Swollen, tender groin lymph nodes (inguinal adenitis)
In about 30–60% of patients, the lymph nodes in the groin become swollen, painful, and tender. They may be enlarged on one side or both sides. This is the body’s immune response to the infection. IUSTI+1
6. Bubo formation (fluctuant groin abscess)
Sometimes the swollen nodes form a bubo, a large lump filled with pus. The skin over the bubo may become thin, red, and very painful. The bubo can burst and release pus through the skin if not treated. IUSTI+1
7. Multiple ulcers in women
Men often have one main ulcer, but women may have several ulcers, sometimes hidden inside the vulva, vagina, or cervix. This can make them harder to see, and symptoms may be less obvious or confused with other conditions. MalaCards+1
8. Painful urination (dysuria)
When an ulcer is near the urethral opening, urine touching the sore can cause burning or sharp pain when passing urine. Some people try to avoid urinating because of this discomfort. MSD Manuals+1
9. Pain during sex (dyspareunia)
Ulcers in or around the vagina or on the penis can make sexual activity very painful. Many patients stop having sex because of this symptom, which is often one of the reasons they seek medical help. Wikipedia+1
10. Foul-smelling discharge from ulcers
The ulcer may ooze fluid or pus that has a bad odor, especially if other bacteria join the infection. This discharge can stain underwear and cause embarrassment and distress. DermNet®+1
11. Fever and general feeling of illness (in some cases)
Most people have mainly local symptoms, but some may develop mild fever, fatigue, or malaise, especially if there are large buboes or secondary infections in the ulcer. NCBI+1
12. Pain when walking or sitting
Large ulcers or groin buboes can cause pain while walking, sitting, or moving the thighs, because these actions put pressure on the inflamed area. IUSTI+1
13. Scarring after healing
Even after good treatment, ulcers may heal with scars. These scars can change the appearance of the genital area and sometimes cause emotional distress or body image concerns in affected people. AccessMedicine+1
14. Increased risk of acquiring or passing on HIV
Chancroid ulcers break the natural skin barrier, so HIV can pass more easily through these open sores. People with chancroid are at higher risk of catching or spreading HIV if exposed. NCBI+1
15. Asymptomatic or mild cases in some people
Sometimes the ulcers are small or less painful, especially in women, and may go unnoticed for a while. This makes it easier for the infection to continue spreading quietly in the community. MalaCards+1
Diagnostic tests for skin ulcus molle
Doctors usually diagnose chancroid using a mix of history, physical exam, and laboratory tests, and by ruling out other causes of genital ulcers such as syphilis and herpes. CDC+1
Physical exam–based tests
1. Full medical history and sexual history
The doctor asks about the start and progress of the sores, pain, number of partners, condom use, travel, and any previous STIs. This helps them understand the risk of chancroid and other infections and guides which tests are most important. World Health Organization+1
2. Visual inspection of ulcers
The clinician carefully looks at the ulcers on the genitals or other skin areas. They note number, size, edge character, base appearance, pain, and location. The pattern of soft, painful, ragged ulcers suggests chancroid but is not enough by itself to confirm it. DermNet®+1
3. Palpation of ulcer edges and base
With gloved hands, the doctor gently feels the edge and base of the ulcer to check if it is soft or firm, tender or not. A soft, very tender ulcer supports chancroid, while a firm, non-tender ulcer suggests syphilis. IUSTI+1
4. Groin lymph node examination
The clinician palpates the inguinal lymph nodes to look for swelling, tenderness, or fluctuation (a sign of pus). Enlarged, painful lymph nodes and buboes are common in chancroid and help support the diagnosis. IUSTI+1
5. Full skin and mucosal examination
The doctor checks the rest of the skin, mouth, and anus for other ulcers, rashes, or lesions. This helps detect other STIs or non-infectious skin diseases that could mimic chancroid and ensures nothing important is missed. DermNet®+1
Manual / bedside procedures
6. Bedside swab of ulcer for smear (Gram stain)
A sterile swab is rubbed over the ulcer base to collect fluid. This sample is smeared on a glass slide and stained (Gram stain) to look for small gram-negative rods that might be H. ducreyi. Sensitivity is limited, but it is a simple first step when lab facilities are basic. NCBI+1
7. Bubo aspiration (needle drainage)
If there is a large bubo, the doctor may insert a sterile needle to aspirate (draw out) pus. This relieves pain and also provides material for culture or PCR testing to identify H. ducreyi. IUSTI+1
8. Gentle curettage or scraping of ulcer base
Sometimes a small scraping of the ulcer base is taken with a curette or similar instrument. This gives a richer sample of cells and bacteria for microscopy, culture, or PCR, improving test yield compared with a simple swab. NCBI+1
9. Pelvic and internal genital examination (especially in women)
In women, ulcers can be hidden in the vagina or on the cervix, so a speculum exam is done. This allows the clinician to see and sample internal lesions that might otherwise be missed. MalaCards+1
Laboratory and pathological tests
10. Culture of Haemophilus ducreyi
Ulcer or bubo samples are placed on special culture media in the lab to grow H. ducreyi. If the bacteria grow and are identified, this gives a definite diagnosis. However, the bacteria are delicate, and culture sensitivity is often less than 80%, and not all labs can perform it. NCBI+1
11. PCR / NAAT for Haemophilus ducreyi
Polymerase chain reaction (PCR) or other nucleic acid amplification tests detect the genetic material (DNA) of H. ducreyi directly from ulcers or pus. These tests are more sensitive and specific than culture, but many countries still do not have routine access to them. NCBI+1
12. Gram stain microscopy
On Gram stain, H. ducreyi appears as small, gram-negative rods arranged in characteristic patterns (“school of fish” or “railroad tracks”). While this pattern may support the diagnosis, it is not always seen and cannot alone confirm chancroid. ACP Journals+1
13. Syphilis serology (VDRL/RPR and specific treponemal tests)
Because syphilis also causes genital ulcers, blood tests like VDRL or RPR, plus specific treponemal tests, are used to rule out or confirm syphilis. CDC guidelines recommend testing for syphilis in all patients with genital ulcers. CDC+1
14. Herpes simplex virus (HSV) PCR or culture
Genital herpes is another very common cause of genital ulcers, usually with multiple painful blisters and sores. A swab from the ulcer can be tested for HSV by PCR or culture. This helps doctors distinguish herpes from chancroid when the appearance is unclear. NCBI+1
15. HIV testing (antibody and antigen tests)
All people with genital ulcers, including suspected chancroid, should be offered HIV testing, because ulcers increase HIV risk and because HIV can change the course of chancroid. Knowing HIV status helps with counseling and overall STI management. World Health Organization+1
16. Complete blood count (CBC) and inflammatory markers
Blood tests like CBC, ESR, or CRP may show signs of infection or inflammation (e.g., increased white blood cells). These tests are non-specific but can help assess general health and detect complications like secondary bacterial infection. NCBI+1
17. Bacterial culture for other organisms
Sometimes the ulcer is mixedly infected with other bacteria. A broad bacterial culture may identify additional germs that need treatment, such as staphylococci or streptococci, especially in chronic or foul-smelling ulcers. DermNet®+1
18. Histopathology (biopsy in atypical cases)
If the ulcer does not heal as expected, or if cancer or other diseases are suspected, a small skin biopsy may be taken and examined under a microscope. Histology can show patterns of inflammation and help exclude conditions like squamous cell carcinoma or unusual infections. DermNet®+1
Electrodiagnostic tests (rare and mostly for complications)
19. Nerve conduction studies (only if neuropathic pain or other nerve disease is suspected)
Electrodiagnostic tests like nerve conduction studies are not routine for chancroid. In rare cases where there is persistent nerve-type pain or suspicion of another neurological problem, they might be used to check the function of nearby nerves, but this is exceptional. AccessMedicine+1
20. Imaging tests such as ultrasound of groin lymph nodes
Simple imaging, especially ultrasound, can be used to look at enlarged groin nodes. Ultrasound helps see whether the node is solid or filled with pus, guiding decisions about aspiration or drainage of buboes. Other imaging (CT or MRI) is rarely needed, reserved for severe complications or deep infections. IUSTI+1
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The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: December 21, 2025.
