Brown pigmentation on nails, ear cartilage

Introduction Brown pigmentation of nails and ear cartilage is one of the clinical symptoms of brownish yellow disease. Ochronosis is due to the lack of homogentisate oxidase in the body, which causes intermediates of phenylalanine and tyrosine. Uric acid can not enter the health search one step oxidative decomposition, accumulate in the body to darken the skin, sclera, cartilage color, while uric acid causes cartilage and other connective tissue pigmentation, degenerative arthritis of the spine and peripheral joints. Therefore, it is also called brown yellow disease. On the other hand, urinary acid is excreted in the urine, and it is alkalized and oxidized in the urine to make the urine color black. It is also called black uric acid (Alkaptonuria). The disease is rare as a rare hereditary disease. Foreign reports have a prevalence rate of 3 to 5 per million population. Because the uric acid is easily deposited on the cartilage, the joint is denatured. In the clinical, joint disease often occurs, which is called brown disease joint disease.

Cause

(1) Causes of the disease:

The disease is a rare autosomal genetic disease. Its exact autosomal variation is still unclear.

(2) Pathogenesis:

The metabolic pathway by which phenylalanine and tyrosine are converted to acetoacetate, and uronic acid (HGA or 2,5-dihydroxyphenylacetic acid) is the last compound containing a complete aromatic ring in this metabolic pathway. The enzyme that catalyzes the cleavage of the aromatic ring is urinary acid oxidase, which is normally present in the soluble part of the liver and kidney tissues. This enzyme is highly specific for the breakdown of uric acid and does not contain this enzyme in tissues other than liver and kidney. In this patient, the activity of this enzyme is completely absent in the liver and kidney, and as a result, the uric acid is not decomposed into acetoacetate and fumaric acid, so that other metabolic mechanisms are needed to treat the uric acid. The kidney has a high clearance rate of uric acid, and the renal tubule actively secretes uric acid. Once the kidney excretes the uric acid, it gradually oxidizes to form a polymer that causes urinary discoloration. The mechanism by which uric acid is deposited on tissues causing brown jaundice is still unclear. Uric acid has a tendency to deposit on the skin and cartilage, where it can be combined by physical attraction.

In addition, the decomposition product of homogentisic acid can irreversibly bind to connective tissue to form a polymer which can cause pigmentation. After the tissue is stained, the texture is fragile and may break, resulting in degenerative lesions in the intervertebral disc and joint. In addition, homogentisate can also directly act on collagen synthesis by inhibiting lysyl hydroxylase.

Pathology: connective tissue and cartilage blackening are the basic pathological changes of this disease. Uric acid can be deposited on the skin, cornea, cartilage, tendons, ligaments, large intima, endocardium, thyroid, lungs and kidneys, making these organs black, involving cartilage can lead to exfoliation of subchondral bone .

an examination

Related inspection

Urine concentration test urine routine

1. Brownish yellow disease: patients with aciduria take a long time to show clinical browning. Most patients develop brown pigmentation in nails and ear cartilage (mainly in the ear and ear) at 20-30 years old. And in the costal cartilage, laryngeal cartilage tracheal cartilage conjunctiva and even the cornea, such as coal black pigmentation patients sweat can also be brown, can be dyed brown and yellow clothing under the armpits and groin.

(1) Joint disease: The most serious complication of this disease is joint disease. Unlike rheumatoid arthritis, this disease mainly invades the large joints such as the spine, shoulders, and hips, while the ankles and small joints of the hands and feet are rarely affected. Male patients develop early and heavier, knee joints are most often involved, and the degree of damage is also the heaviest. Spinal lesions are also the most common bone and joint damage in this disease, often manifested as lower back stiffness and pain. The lesions occur in the lumbar vertebrae. As the disease progresses, it can affect the thoracic vertebrae, hinder the movement of the spine, and the physiological curvature of the spine disappears. Disc herniation and calcification are also characteristic of this disease. Typical patients are antelope duck gait. After a mild trauma to the affected knee joint, it can cause fluid accumulation in the joint cavity. The synovial fluid is non-inflammatory and mainly contains monocytes. Arthroscopic examination showed that the synovial membrane was black stained. Joint contracture can occur gradually after the disappearance of the joint cavity effusion.

(2) Skin lesions: It is caused by the deposition of urinary acid pigment particles in the dermis and sweat glands, which are mostly distributed brown at the tip of the nose, ear and rib-cartilage. They can also be distributed in the nose and cheeks. The armpits and perineum are parts of the sweaty glands that are often dark brown or blue-black. The clothes that are close to these parts are dyed brown. Occasionally nails can also be blue-gray in the later stages of the disease often accompanied by auricular stiffness and calcification. Brown-yellow pigmentation can sometimes occur in extraocular tissues such as the sclera, conjunctiva, and cornea. The sclera is brown and is usually limited to the exposed part of the cleft palate

(3) Others: Some patients may have heart valve disease. Male patients with a longer course of aortic valve stenosis may develop chronic prostatitis, which is caused by the formation of stones in the alkaline secretion of the prostate. Porous black kidney stones can occur in a small number of patients.

2. Aciduria arthritis: The accumulation of metabolic substrates such as uric acid and acid in the joint capsule bursa can cause damage to the articular surface. Early symptoms include limited joint pain in the knee, hip, shoulder and other joints. Late can involve the spine. However, the hands, wrists, elbows, ankles, and foot joints are less affected. The joints may have red and swollen exudate, the synovial fluid is non-inflammatory, and there are more pyrophosphate and calcium salts deposited.

3. Urine changes: The urine of patients with typical urinary acid uric acid is black, or after the urine is left for a period of time, it first turns black from the surface, and gradually all the urine changes to dark brown.

4. Complications: The knee joint of the lesion may cause fluid accumulation in the joint cavity after mild trauma. The synovial fluid is non-inflammatory and mainly contains monocytes. Arthroscopic examination showed that the synovial membrane was black stained. After the joint effusion disappears, the patient may have contraction of the joint. Some patients may have heart valve disease and mainly aortic valve stenosis. Chronic prostatitis can occur in male patients.

Differential diagnosis

Differential diagnosis

Black urine, typical pigmentation of the skin, and characteristic X-ray findings of the large joints such as the spine, shoulders and knees constitute the three major characteristics of brownish yellow disease, which can be diagnosed accordingly. Special examination of hematuria for hematuria can be performed when conditions permit.

Other causes of urinary blackening, such as hematoporphyria, myosinuria, bilirubinuria, and hematuria, should be excluded in the differential diagnosis. It is not difficult to distinguish from brownish yellow disease based on the clinical characteristics of these diseases and related laboratory tests. Long-term use of mepacrine (Api) can cause brown pigmentation-like pigmentation, and clinical care should be taken not to confuse this iatrogenic pigmentation with brownish yellow disease. Multiple application of phenol (carbolic acid) for the treatment of skin ulcers can also cause yellow pigmentation, which should be noted.

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