Hydroxyapatite deposition disease
Introduction
Introduction to hydroxyapatite deposition Hydroxyapatite is the main mineral salt of bones (including teeth). Hydroxyapatite deposition is the deposition of hydroxyapatite in bone and extra-dental tissues, which is ectopic calcification. Ectopic calcification can occur in various parts of the body. Including local and systemic connective tissue, joints and tissues around the joints, calcification of joints and tissues around the joints, often without symptoms, but sometimes can cause acute arthritis and many other chronic joint diseases, the disease is generally mild, or even There are no symptoms, but it can also cause joint destruction and deformity. Joint replacement is required. Hydroxyapatite is deposited around the joints and can occur at any age, but it is more common in the elderly. basic knowledge The proportion of illness: 0.003% Susceptible people: the elderly Mode of infection: non-infectious Complications: joint pain osteoarthritis
Cause
Causes of hydroxyapatite deposition
Etiology
The cause of HA deposition is unclear. Normal connective tissue contains anti-calcification inhibitors. In vitro tests have shown that inorganic pyrophosphate, proteoglycan aggregates and non-collagen proteins have the effect of preventing calcification of tissues. If due to tissue trauma, aging, normal The inhibition of calcification is weakened; or due to the presence of core forming agents in the tissue, which contribute to the mechanism of cellular calcification; or due to metabolic disorders, elevated concentrations of local solute can promote the abnormal deposition of calcium salts.
According to current clinical findings, abnormal deposition of HA can occur in the following three cases:
Unexplained idiopathic calcification (30%):
The deposition of HA occurs mostly in easily damaged joints, relative ischemic tendons, diseased tissues (local or systemic connective tissue diseases) or lesions, and elderly patients, indicating that normal tissues are important for preventing calcium formation, metabolism Obstruction, hypercalcemia, hyperphosphatemia, hyperparathyroidism, vitamin D poisoning, diabetes, chronic renal failure, can promote calcification, indicating that metabolic factors play a role in this, and patients with idiopathic calcification, and There are no obvious reasons, and this patient often has multiple sites, multiple joints involved, and its deposition often contains other crystalline components, large deposits, or family history, indicating that this patient has systemic calcification promoting factors.
Tissue damage (dystrophic calcification).
Hypercalcemia or hyperparathyroidism (metastatic calcification).
Prevention
Hydroxyapatite deposition prevention
Because the cause is unclear, there is currently no effective prevention method. Pay attention to safety, do a good job of protection, reduce and avoid accidental injuries caused by adverse factors, can play a certain preventive role, early detection, early diagnosis, early treatment is the key to the prevention and treatment of this disease. Once the disease occurs, it should be actively treated to prevent the occurrence of complications.
Complication
Hydroxyapatite deposition complications Complications, joint pain, osteoarthritis
A common complication of the disease is joint deformity.
Symptom
Symptoms of hydroxyapatite deposition disease Common symptoms Joint swelling fascia pain Joint fluid exudation Tendonitis Synovial inflammation Joint pain Shoulder joint activity limitation
As mentioned earlier, HA is deposited in the joint or around the circumference of the tissue, without any symptoms, acute inflammation or chronic arthritis can occur, in clinical manifestations:
Joint inflammation
Can occur any age and gender, often after injury or spontaneous start suddenly, pain is obvious, local tenderness, gradually relieved or completely subsided after a few days, shoulder joint involvement accounted for 705, lesions involving the shoulder sag, tendon, limited mobility Local skin may be red and swollen. Other common joints include knee, hip, wrist and knuckle. Sometimes chronic joint pain, joint activity often involves pain caused by affected tendon.
Synovitis
Acute synovitis can involve multiple joints. Sometimes, except for the discovery of HA crystal in inflammatory synovial fluid, there are no other obvious reasons. The number of synovial fluid cells is often below 2×109/L (2000/mm3). Sometimes up to 50 × 109 / L (50000 / mm3), mainly monocytes, occasionally neutrophils predominate.
3. Osteoarthritis
The joints behave like primary osteoarthritis, but the affected joints are different. The crystallization of HA can be found in synovial fluid, synovial tissue and cartilage. This crystallization is the cause or result of joint lesions. HA crystals can cause inflammation and can directly damage joints as described above.
4. Destructive joint disease
More common in knee and shoulder joints, showing pain, swelling, limited mobility, mostly in elderly patients, symptoms can be mild or severe pain, from joint dysfunction to joint erosion, atrophy, destruction, deformity, joint fluid cells less than 1 × 109/L can also be a bloody exudate, and there is HA crystal in the joint fluid.
Examine
Examination of hydroxyapatite deposition disease
The number of cells in the synovial fluid of the joint is generally not high. The number of cells in chronic joint disease is often below 1×109/L, and acute, subacute is also often below 2×109/L, mainly monocytes.
X-ray examination generally has no special diagnostic value, but severe joint lesions show erosion, destruction and hyperplastic changes. Fine calcification deposits cannot be shown on X-ray images, while bulk crystallization complexes show calcification on X-ray films. The shadow, in the adhesion of the diaphragm around the joint, presents spherical irregular calcified shadows, no trabecular structure inside, and does not have the "linear" appearance like the pyrophosphate cartilage calcification, this calcification shadow, In the process of acute arthritis, dynamic changes can occur, and clear and clear shadows are seen first, then soft, diffuse, and gradually disappear, which is estimated to be caused by crystallization and phagocytosis.
In the synovial fluid, the deposition of HA in the synovial tissue can be screened by alizarin red staining to observe whether there is a red spherical calcium-containing substance. Only the polymerized spherical HA knot can be seen in the light microscope, and the monomer crystal needs to be crystallized. Resolved by electron microscopy.
Diagnosis
Diagnosis and identification of hydroxyapatite deposition
diagnosis
In clinical practice, patients with suspected hydroxyapatite deposition may be examined by X-ray examination, then the synovial fluid is taken for microscopic examination with alizarin red staining, and appropriate specimens are selected for electron microscopy to make clinical Diagnosis, and accurate crystal identification depends on electron diffraction or X-ray diffraction or infrared spectroscopy. The disease can be seen in the joint and around the joint HA deposition. Acute or chronic damage is seen in the joint capsule, tendon, bursa or articular surface. Excessive joints are the most likely to occur, and X-ray examinations generally have no diagnostic value. Affirmative diagnosis remains to be determined by HA crystallization.
Differential diagnosis
The disease should be differentiated from arthritis caused by other causes.
