Oxalosis is a rare hereditary disease characterized by excessive formation of oxalic acid and accumulation of its salts (oxalates) in organs. The pathology is manifested by interstitial nephritis, the formation of kidney stones, the deposition of calcium salts in the renal tissue, periodic attacks of renal colic and the gradual development of chronic renal failure. The diagnosis is made on the basis of an increase in the excretion of oxalates in the urine, ultrasound of the kidneys, excretory urography. The basis of therapeutic measures is drug therapy, diet therapy, compliance with the drinking regime and control of diuresis.
Oxalosis (primary hyperoxaluria) is a rare metabolic disorder in which there is excessive production and deposition of calcium oxalate in parenchymal organs, mainly in the kidneys. It has a hereditary character. Among infants, primary hyperoxaluria occurs in 1 case per 120 thousand newborns. According to experts in the field of practical urology, the prevalence is 1-3 cases of hyperoxaluria per 1 million population.
Pathology develops as a result of damage to a gene localized in the long arm of chromosome II. The disease is based on hereditary enzyme deficiency. The disease is usually transmitted by autosomal recessive type, there are cases of autosomal dominant inheritance. In the first case, there are no clinical signs of hyperoxaluria in heterozygotes. In families with oxalosis, the incidence of the disease among the closest relatives varies from 30 to 35%.
There are two types of primary hyperoxaluria with common clinical signs. With type 1 hyperoxaluria, there is insufficient production of alaninglioxylate aminotransferase in liver cells, as a result of which there is no conversion of glyoxylic acid to formic acid. Glyoxylic acid under the influence of lactate dehydrogenase is transformed into oxalic acid, as a result, glyoxylate and calcium oxalate accumulate and are excreted in the body. Type 1 oxalosis occurs in 70% of cases.
With type 2 hyperoxaluria, there is a lack of D-glycerate dehydrogenase, which is involved in the conversion of glyoxylic acid into glycolate. Oxalic and glyceric acids accumulate. Oxalic acid is converted into oxalates and excreted in the urine. This type of oxalosis is found among the inhabitants of the Ojibwa Indian tribes from Manitoba. The pathogenesis of the formation of stones and calcinates in parenchymal organs in primary hyperoxaluria is associated with the insolubility of calcium oxalate.
Clinical signs of the disease appear at the age of 3-4 years. There are frequent attacks of renal colic, episodes of high blood pressure, enuresis. Hematuria, proteinuria, and leukocyturia are detected in the urine. Frequent urinary tract infections (cystitis, urethritis, pyelonephritis) are associated with deterioration of the patient’s condition, increased body temperature, weakness. With the accumulation of oxalates, urolithiasis develops, which is usually bilateral in nature.
With a generalized form, osteoporosis is detected in patients, spasms of arterioles and capillaries often occur, cardiac conduction is gradually disrupted, signs of heart failure appear. In the late stages of oxalosis, autointoxication (uremia) develops as a result of impaired kidney function and retention of nitrogenous compounds.
The most dangerous complication of oxalosis is chronic renal failure (CRF). According to statistics, 80% of deaths from irreversible kidney damage occur before the age of 20. With the progression of the disease, chronic renal failure can turn into acute. Against the background of uremia, children develop mental and physical retardation, dyslexia, bone and joint lesions (osteoporosis, arthritis), cardiovascular system (myocarditis, atrioventricular blockades, heart failure). With generalized oxalosis, secondary hyperparathyroidism occurs, accompanied by increased bone fragility and joint deformation.
The diagnosis of oxalosis is carried out by a nephrologist, based on the study of family history, history of the disease, clinical picture, as well as on the data of laboratory and instrumental studies. In the analysis of urine, an increased level of oxalates, glycolic and glyoxylic acid is determined in the absence of their excessive consumption with food. In primary hyperoxaluria, the excretion of calcium oxalate is at least 200 mg / day. For type 1 of oxalosis, the excretion of glycolic acid is characteristic, and for type 2 – glyceric acid.
With the help of excretory urography, kidney stones and calcification are detected. During ultrasound of the kidneys, small-focal compacted areas are determined along the course of the pyramids and in the cup-pelvis system. Additionally, densitometry and scintigraphy are performed to detect osteoporosis. In severe cases, bone marrow puncture is performed with the detection of oxalates. In the presence of cases of oxalosis in family members, prenatal screening is performed by biopsy of chorionic villi.
Genetic research determines mutations of genes responsible for oxalate metabolism (AGXT, GRHPR, HOGA1 genes). Differential diagnosis of oxalosis is carried out with secondary hyperoxaluria, which can develop with a food overdose of glycine contained in meat, liver, cereals.
There is no specific treatment for primary hyperoxaluria. The main goal of oxalosis therapy is to prevent exacerbations and the development of renal insufficiency, reduce the level of oxalates and prevent kidney stones.
- Drug therapy. In clinical practice, pyridoxine preparations are used, which contribute to a temporary decrease in the formation of calcium oxalate.
- Diet therapy. The diet provides for a limited intake of oxalic acid and increased calcium intake. When following a diet, the following foods should be excluded from the diet: fatty meat dishes, sorrel, spinach, coffee, tea, chocolate, beets, smoked meats. It is recommended to eat cereals, vegetable broths, melons (pumpkin, melon), zucchini, apples, dairy products, cucumbers, dried fruits.
- Drinking regime. Patients with oxalosis should increase the consumption of pure still water by 500-1000 ml compared to the norm. It is necessary to monitor the frequency of urination, which should be carried out every 2-3 hours. These measures contribute to the dilution of urine and reduce the risk of nephrolithiasis.
Prognosis and prevention
In the absence of observation and treatment, the prognosis for oxalosis is unfavorable. In 50% of patients with primary hyperoxaluria, signs of renal failure appear at the age of 13-15. At the age of 30, chronic kidney damage is diagnosed in 80% of patients with oxalosis. Early detection of the disease, a strict diet and drinking regime can delay the formation of kidney stones and the development of kidney failure for years. Prevention of complications from the urinary system includes dispensary supervision by a therapist or pediatrician. The patient needs to take a general urine test quarterly, Zimnitsky samples, perform kidney ultrasound once a year and visit a nephrologist.