| disease | Syphilis of Bone and Joint |
Syphilis is a sexually transmitted disease left over from the old society, and new cases have emerged in recent years. Bone and joint syphilis is a manifestation of systemic syphilis infection in the bones and joints. Depending on the time and route of infection, syphilis is divided into congenital and acquired types. Congenital syphilis occurs when the syphilis spirochete in a pregnant woman invades the placenta and then enters the fetus through the umbilical vein, causing disease. This type of syphilis can lead to bone and joint lesions early on. Acquired syphilis occurs when the syphilis spirochete enters through skin or mucous membrane contact, invading through cracks or damaged areas, and in rare cases, it can be transmitted through blood transfusion.
bubble_chart Etiology
Syphilis is caused by infection with the syphilis spirochete and is a type of sexually transmitted disease. Acquired syphilis in the initial stage [first stage] does not affect bones and joints, but the second and late stages [third stage] can both lead to bone and joint lesions.
According to the progression of the disease, syphilis can be divided into the late stage [third stage]: ① Initial stage [first stage] syphilis. This is a proliferative inflammation that occurs after local infection and can form a "hard chancre." ② Intermediate stage [second stage] syphilis. This is the rash stage, usually appearing 1 to 3 months after infection. The spirochete spreads throughout the body via the bloodstream, causing widespread lymph node enlargement. ③ Late stage [third stage] syphilis. During this stage, bones, liver, heart blood vessels, and the nervous system can all be affected. Symptoms may appear months to decades later.
Bone and joint syphilis can also be divided into congenital and acquired types. Except for the unique manifestations of osteochondritis in congenital early bone syphilis, the clinical manifestations, pathological changes, and X-ray findings of congenital and acquired syphilis are generally similar.bubble_chart Pathological Changes
The spirochete of syphilis travels through the bloodstream to the bone tissue, where it lodges in the metaphysis, causing non-suppurative inflammation. If the body's resistance is strong, the pathogen can be eliminated and the inflammation subsides; otherwise, the tissue may be further damaged, leading to gummatous lesions. Bone destruction can stimulate the thickening of the bone membrane, resulting in new bone formation. The lesions may also penetrate the tissue, causing fistulas and secondary infections. Joint involvement can manifest as painless, symmetrical arthritis or gummatous joint manifestations.
bubble_chart Clinical Manifestations
(1) Congenital early syphilis occurs before birth during the late stage of pregnancy [third stage]. Symptoms can appear as early as 2-3 weeks after birth or as late as 6-7 months after birth. About 70-80% of infants with congenital syphilis may have osteochondritis lesions. Since the lesions are located around the epiphysis, it is more appropriate to refer to the condition as osteitis. It commonly affects the metaphysis of long bones, with a large number of inflammatory cells infiltrating and granulation tissue forming near the epiphysis, leading to impaired ossification, widening of the epiphysis, and irregular epiphyseal lines. The cartilage often shows proliferation of immature cells, and although the intercellular matrix may calcify, the osteoblasts are inactive, preventing the calcified tissue from forming trabeculae. As the disease progresses, the calcified matrix is replaced by fibrous tissue and granulation tissue, forming syphilitic granulomas. On X-rays, the metaphysis appears widened, with a band-like area of increased density distally, representing the calcified cartilage zone. Below this, there is an irregular osteoporotic area composed of granulation tissue, fibrous tissue, and osteoid tissue. The distal epiphyseal line becomes irregular and serrated due to asynchronous ossification of cartilage cells. In severe cases, epiphyseal separation may be seen. Periosteal proliferation around the metaphysis may appear as periostitis. Common sites of involvement include the femur, humerus, ulna, and radius, often symmetrically.
The affected limb may show localized swelling, tenderness, muscle atrophy, and a flaccid, drooping appearance. The infant may avoid voluntary movement and cry during passive movement, showing signs of dysphoria and restlessness. Clinically, this is referred to as pseudoparalysis. The child may also have syphilitic keratitis, rashes, mucous membrane patches, rhinitis, and nail damage. Systemic manifestations include weakness, emaciation, loose skin with many wrinkles, low-grade fever, and difficulty feeding.When multiple skeletal lesions are present in a newborn or infant, syphilis should be considered. The radiographic features of bone lesions aid in diagnosis. However, it is important to differentiate syphilis from scurvy and rickets. Syphilis typically occurs within the first six months of life, while other diseases present at older ages, aiding in differentiation.
(2) Congenital advanced stage syphilis can occur at any age but is most common between 5-15 years. It primarily manifests as periostitis, osteitis, osteomyelitis, and synovitis. The pathological changes are similar to those of late-stage [third stage] acquired syphilis. The main features include significant osteogenic changes in the tibia, femur, and skull. For example, the anterior periosteum of the tibia may show marked hyperplasia, giving it a saber-like appearance, hence the term "saber tibia" or "saber shin." The affected area may show swelling, tenderness, and sometimes severe, drilling-like bone pain, but there is no systemic fever, and the white blood cell count is normal. Severe subperiosteal infections may invade the cortex, but gummatous osteomyelitis is rare.
The child may have a saddle nose and neurogenic deafness. Syphilitic dactylitis may cause swelling of the fingers and carpal bones without pain. On X-rays, the phalanges appear spindle-shaped with increased density and gummatous destruction on the surface. Older children (over 8 years) may have bilateral knee joint effusions that are painless, minimally affect movement, and resolve spontaneously. Recurrent episodes do not damage the joint, and the joint fluid contains many mononuclear cells with minimal inflammation. X-rays show no positive findings, a condition known as Clutton's joints.
Both the child with congenital bone and joint syphilis and the mother will have a positive Wassermann serum reaction.(3) Acquired syphilis involves bone and joint pathological changes during the second and late [third] stages of syphilis. The intermediate [second] stage may affect the periosteum, bone cortex, cancellous bone, and synovium, including joint capsules, bursae, and tendon sheaths. Periostitis is the most common, accounting for about two-thirds of cases. It commonly affects the tibia, ulna, radius, fibula, femur, and humerus, typically occurring in adults during the syphilitic rash stage. Early X-rays may show no changes, but the advanced stage reveals spindle-shaped cortical hyperplasia. The bone surface may be smooth or show moth-eaten defects. Inflammation within the medullary cavity is rare.
In the late stage [third stage], manifestations are predominantly osteitis and osteomyelitis. Adults typically develop the disease 3 to 7 years after syphilis infection. Cortical bone lesions are mainly characterized by hyperplasia. It can also be accompanied by moth-eaten bone destruction, which is a manifestation of gumma sexually transmitted disease changes. It can also occur within the medullary cavity and may penetrate soft tissues to form fistulas, with sequestrum being rare. The skull is a common site of occurrence. Among long bones, the tibia, ulna, radius, and humerus are more frequently affected, and the lesions often involve the entire bone.
When bones and joints are involved, the clinical manifestations are mainly pain, which varies in severity. In severe cases, the pain can be intense, like a drilling sensation, often intermittent, alleviated after activity, and worsened during rest and at night, affecting sleep. Sometimes there is only mild pain. The local skin at the lesion site may be swollen and tender, often accompanied by ulcers and fistulas. Joint lesions manifest as arthralgia and reactive effusion, and some may present as gummatous arthritis. In advanced stages, spinal pulmonary tuberculosis can lead to neurogenic arthritis, commonly known as Charcot's joint, clinically presenting as joint enlargement, instability, subluxation or dislocation, and increased range of motion, characterized by the absence of pain. X-rays show sclerosis, destruction, dislocation, osteophyte proliferation, and free bodies of varying sizes at the bone ends.
When the skull is involved, multiple irregular masses with elastic and tough consistency can be palpated on the skull, sometimes breaking through to form ulcers. If it progresses deeper, it can also invade the inner table of the skull and penetrate inward, causing syphilitic meningitis.
Patients with advanced stage syphilis may develop syphilitic gummatous arthritis, often affecting the large joints of the limbs, with the knee joint being the most commonly involved. There is mild pain and limited movement, and a few syphilitic gummas may ulcerate and form fistulas. X-ray findings show soft tissue swelling of the joint, with bone proliferation and destruction.
The diagnosis of syphilis is not particularly difficult. Based on its medical history, time of onset, clinical manifestations, X-ray changes, and a positive Kahn serum reaction, misdiagnosis and confusion with fistula disease can be avoided. However, early syphilitic bone and joint lesions should be distinguished from wind-dampness arthritis and subcutaneous nodular arthropathy. In advanced stages, it should be differentiated from chronic sclerosing osteomyelitis and osteosarcoma.
bubble_chart Treatment Measures
The treatment principle for syphilis of bone and joint combines systemic and local treatments, with systemic therapy being the primary approach.
Once the diagnosis is confirmed, treatment should be initiated as early as possible. Both spouses of syphilis patients and the parents of pediatric patients must undergo treatment simultaneously. A comprehensive physical examination should be conducted before treatment. Commonly used anti-syphilitic therapies include:
1. Penicillin Oil Therapy: For congenital syphilis patients under two years old, the total course dosage is calculated at 350,000 units per kilogram of body weight, divided into 10 intramuscular injections, administered daily or every other day. For children aged 2 to 14 years, the dosage is 250,000 units per kilogram of body weight. Generally, the total course dosage does not exceed 6 million units. Two treatment courses are administered, with a two-week interval between them.
For adults with intermediate stage (second stage) and advanced stage syphilis, the total course dosage is also 6 million units, with 600,000 units injected daily. For recurrent syphilis, the total course dosage is 12 million units, with 600,000 units injected daily for 20 days.
2. Arsenic-Bismuth Combination Therapy: Used for patients allergic to penicillin.
During anti-syphilitic treatment, attention should also be paid to local symptomatic treatment. For example, the affected limb should be immobilized. A gypsum splint or external fixation brace should be used to maintain the affected limb in a functional position. Ulcer wounds should be cleaned and dressed promptly, or the lesion should be removed. For patients with severe pain due to long bone membrane inflammation, a decompression window can be created to significantly alleviate pain. However, treating certain deformities and Charcot joints can be more challenging.
Syphilis is primarily a sexually transmitted infectious disease and is preventable. From a long-term perspective, it is crucial to vigorously promote awareness of the causes of syphilis and its harm to the human body, improve cultural and moral standards, and strengthen legal oversight. At the same time, establishing a sexually transmitted disease prevention and control network is essential to ensure early diagnosis and timely, appropriate treatment for syphilis patients.