Phosphate diabetes is a disease in which the body excretes an excessive amount of phosphate through the urine. In healthy individuals, the phosphate is filtered from the so-called preurine. The kidneys are primarily responsible for this process. Due to the excretion of phosphate, the growth of bones is disturbed, so that phosphate diabetes has similarities to rickets.
What is phosphate diabetes?
Phosphate diabetes is sometimes called vitamin D-resistant rickets or idiopathic Debré-de Toni-Fanconi syndrome. Fundamental to understanding the disease is the fact that calcium is deposited in human bone. Phosphate is significantly involved in this process. The disease usually begins in childhood. In general, phosphate diabetes is twice as common in females as in males. However, in most cases the course of the disease is milder in girls. Phosphate diabetes is not contagious for other people. In principle, the disease is a form of rickets caused as a result of hypophosphatemia.
Causes
The development of phosphate diabetes has a genetic component. The primary cause is a mutation on a specific gene located on the X chromosome. This also explains why the disease occurs twice as often in women as in men. In addition, it is a dominant mutation. In this way, one mutant allele is sufficient to trigger phosphate diabetes. In principle, however, the exact mechanism of development is still largely unexplored. Some physicians suspect that the corresponding gene is involved in the synthesis of membrane proteins. In this way, the retention of phosphate in the organism or in the kidneys is controlled. Due to the mutation, however, this process is defective. In principle, calcium and phosphate are interconnected in human blood. This is also called calcium-phosphate product. If the amount of phosphate decreases, so does calcium. As a result, a smaller amount of calcium is stored in the bones. However, calcium is a mandatory building block for bones to ensure their stability. For this reason, large amounts of calcium are necessary to ensure healthy bone growth in childhood. Therefore, characteristic deformations of the bones form in the context of phosphate diabetes. In addition, phosphate diabetes leads to the fact that despite the insufficient concentration of phosphate, no vitamin D is secreted by the organism. This is a common process for regulation in healthy individuals. Inadequate reabsorption of phosphate takes place in the kidneys. Therefore, hypophosphatemia is detectable in the serum of the blood. As a result, the mineralization of the bones runs disturbed.
Symptoms, complaints, and signs
Phosphate diabetes is manifested by various symptoms. In the majority of cases, the symptoms of the disease begin in two-year-old children. The first deformations of the bones are visible in the patients. These appear, for example, in the form of pronounced bow legs and a genoa. The gait is often wide-legged and waddling. In addition, the affected children are often too small for their age and may also suffer from impaired development of the teeth. In some cases, middle ear hearing loss develops because the small bones in the ear canal do not form properly. This is especially the case if adequate treatment is not given. It is also possible that calcium accumulates in the kidney as a result of phosphate diabetes.
Diagnosis and course of the disease
The diagnosis of phosphate diabetes can be made with the help of various examinations. First, a medical history is taken between the affected patient or his or her parents and the physician. Then, the clinical symptoms are subjected to a thorough review. Due to the age of the patient during the initial manifestation, suspicion often quickly falls on phosphate diabetes. During blood tests, decreased concentrations of phosphate are detectable in the serum of the blood. At the same time, calcitriol and calcium are present in the usual amounts. X-ray examinations show rachitic deformations of the bones. These show up mainly in the so-called growth areas on the forearm bones.In advanced stages of the disease, the changes are also detectable in the knee joints. In addition, there are indications of the presence of osteomalacia. It is also important to perform a thorough differential diagnosis. It is relevant here that phosphate diabetes has certain similarities to hypophosphatasia. Therefore, confusion between the two diseases may be possible. In addition, the presence of renal osteodystrophy should be checked.
Complications
Phosphate diabetes, which runs in families, leads to complications such as damage to bones or teeth and renal dysfunction simply because of the X-linked inherited hypophosphatemic rickets. The metabolic disease often leads to joint pain before it is detected. The joints of the legs twist due to the phosphate deficiency. This leads to a waddling gait, knock knees or bow legs. If the deformities are particularly pronounced due to phosphate diabetes, they must be orthopedically corrected. If this is not done, the now adults are at risk of further complications due to premature wear and tear on the joints. Phosphate diabetes patients can also develop changes in their teeth as a result of the disturbed phosphate balance. Fistulas, suppurated or inflamed root tips can also involve the jawbone. Sufferers are at risk of premature tooth loss if the teeth are not treated promptly. Caries and periodontitis are more common in people with phosphate diabetes. Good dental care is essential to avoid such complications. Further complications can occur during the treatment of phosphate diabetes. The commonly used phosphate and calcitriol therapy shows side effects in at least half of those affected. One of these is increasing renal calcification. If the crystalline deposits in the kidney are severe, this can result in high blood pressure and impaired filtering action of both kidneys. Further treatment therefore requires close medical monitoring.
When should you see a doctor?
If irregularities appear within the growth and development process of the child, a doctor is needed. Deformities of the physique, peculiarities of the bones as well as incorrect postures should be discussed with a doctor. In case of severe bow-legs or knock-knees, crooked posture as well as difficulties in locomotion, a doctor is needed. Peculiarities of gait, unsteadiness or increased risk of accidents and falls should be presented to a doctor. The first irregularities of phosphate diabetes appear in children at the age of about two years. As the disease progresses, an increase in symptoms with a simultaneous decrease in well-being becomes apparent. Disturbances in the growth of teeth or abnormalities in the digestive process must be examined by a physician. If there is impairment of kidney function, refusal to drink or pain in the area of the kidneys, a visit to the doctor should be made immediately. Changes in the appearance of the skin or in urination should be presented to a doctor. If, in addition to the physical complaints, emotional or mental problems are also apparent, consultation with a physician is also recommended. In case of withdrawal behavior, social isolation or apathy, the affected person needs help. Weepiness or conspicuous behavior are to be understood as warning signs. There is a health impairment that should be clarified and examined. Anxiety, feelings of shame, sleep disturbances or loss of appetite are signs of a stress condition that needs to be clarified.
Treatment and therapy
Phosphate diabetes is principally treated symptomatically, since it is not possible to eliminate the causes. The focus of therapy is the administration of calcitriol and phosphate. It is important to start drug treatment as early as possible. In this way, damage and deformation of the bones can be prevented to a certain extent. In addition, regular kidney examinations are necessary, as the development of nephrocalcinosis is favored.
Outlook and prognosis
Phosphate diabetes is a rarely occurring special form of rickets. The first symptoms appear from the second year of life. There are gait abnormalities, short stature, and a conspicuous tooth development disorder. Whether these lead to a differential diagnosis is questionable.However, the prognosis of phosphate diabetes depends very much on how early the disease is detected. If treated promptly, the outlook for young patients is best. If phosphate diabetes is not treated in time, there is a risk of skeletal deformities, as well as permanent sensorineural hearing loss. The skeletal deformities can only be corrected surgically once bone growth has ceased. Until then, a pediatric orthopedist should be consulted. If sensorineural hearing loss already exists, it usually cannot be corrected. However, there are ways to alleviate it. However, the treatment of this disorder is complex and must be carried out with care. In the case of phosphate diabetes, the young patients usually have to be given phosphate and calcitriol. Constant monitoring of urinary calcium excretion is necessary. Calcitriol administration can cause hypercalcemia with nausea and vomiting in overdoses. In addition, nephrocalcinosis may result from the medication. The latter can lead to renal insufficiency. This means years of dialysis. If necessary, there is a need to find a donor kidney. Therefore, regular ultrasound examinations are useful.
Prevention
Measures for the prevention of phosphate diabetes are not known, since the disease is hereditary. Medical examinations should be initiated at the first symptoms of the disease, since a timely start of therapy significantly improves the prognosis of phosphate diabetes.
Follow-up
In most cases, there are no special and direct measures of aftercare available to the affected person in phosphate diabetes, so that in this disease, first and foremost, a rapid diagnosis and also the subsequent treatment of the disease should be carried out. As a rule, self-healing cannot occur, and the disease can lead to severe complications if it is not treated. Therefore, the patient should contact a doctor at the first signs and symptoms of the disease. The treatment itself is carried out with the help of various medications, although a complete cure for phosphate diabetes is usually not possible. Patients are therefore dependent on lifelong therapy. It is always important to ensure that the medication is taken regularly and that the recommended dosage continues to be used in order to alleviate the symptoms properly and permanently. Regular check-ups by a physician are also necessary. Possible malformations of the bones can be alleviated by surgical interventions, although the affected person should in any case take it easy and rest after such an intervention. Possibly this disease reduces the life expectancy of the affected person, although a general prediction about the further course is usually not possible.
What you can do yourself
According to the current state of research, phosphate diabetes is considered to be genetic and cannot be treated causally. Therefore, there are no self-help measures that have a causal effect. However, the sooner the disease is recognized and adequately treated, the fewer the expected late effects. Since congenital phosphate diabetes is already apparent in childhood, it is primarily the parents who are called upon to take action. Anyone who comes from a family in which phosphate diabetes has already occurred should be aware of the symptoms and, even if they themselves are healthy, should monitor their children for them. If growth retardation or other abnormalities become apparent, a doctor must be consulted immediately. It is extremely important to point out to the attending physician that there are cases of phosphate diabetes in the family. Since this disease is a rather rare disorder, there is otherwise a risk that it will be diagnosed too late. However, too late diagnosis often causes maldevelopment of the auditory canal in the affected infant, which is irreversible. Parents should also not leave the treatment of their child to the family doctor alone, but should insist in any case that a doctor is consulted who already has experience with the therapy of phosphate diabetes. Support in finding a suitable doctor can be obtained from the medical association. In addition, a self-help association has also been in existence for some years to advise patients and their relatives.
