Schwartz-Bartter Syndrome: Causes, Symptoms & Treatment

Schwartz-Bartter syndrome is an endocrine disorder associated with increased secretion of antidiuretic hormone (ADH). As a result, too little fluid is excreted by the kidneys. The urine is insufficiently diluted.

What is Schwartz-Bartter syndrome?

Schwartz-Bartter syndrome is also known as syndrome of inadequate ADH secretion, or SIADH for short. It is a disorder of osmotic regulation. Underlying this dysregulation is increased production and secretion of the hormone ADH, also known as vasopressin. Schwartz-Bartter syndrome is often confused with Bartter syndrome. However, this is a disease of the renal tubules that is unrelated to Schwartz-Bartter syndrome proper.

Causes

In more than 80 percent of cases, Schwartz-Bartter syndrome is caused by small-cell bronchial carcinoma. In this case, the disease presents as a paraneoplastic syndrome. A paraneoplastic syndrome is a constellation of symptoms that occurs in the context of tumor disease but is not a direct consequence of tumor growth. Small cell lung carcinoma is a hormone-producing tumor. In the case of Schwartz-Bartter syndrome, the cancer cells produce ADH. Only rarely are other causes of the syndrome found. One possible cause is the uncoupling of pituitary ADH control by physiological stimuli. Such stimuli may result from strokes, brain inflammation, or traumatic brain injury. Schwartz-Bartter syndrome is also observed after severe burns, in pneumonia, or in tuberculosis. Furthermore, it can be observed as a side effect when taking tricyclic antidepressants, serotonin reuptake inhibitors, neuroleptics, cytostatics or antiarrhythmic drugs. In addition, it is shown that there is a transient increased ADH release in almost all patients after surgery.

Symptoms, complaints, and signs

In some cases, Schwartz-Bartter syndrome may be completely asymptomatic. Nonspecific symptoms such as nausea, vomiting, headache, and loss of appetite are common. ADH causes increased reabsorption of water in the kidney. As a result, water excretion is decreased. This condition is called hypotonic hyperhydration symptom. The retained water dilutes the blood so that the concentration of electrolytes is altered. There are decreased levels of sodium, potassium, and phosphate in the blood. The result is metabolic hypochloremic alkalosis. The severity of symptoms depends on the dilution of sodium. In addition to the above non-specific symptoms, personality changes may also occur. Patients are irritable or lethargic. They appear confused. Disturbances of consciousness up to delirium or coma may occur. In addition to muscle weakness and muscle spasms, epileptic seizures or rapid involuntary muscle movements, known as myoclonias, may occur. Neurologic reflexes are increased or attenuated. Water retention is limited to three to four liters. Although this has a drastic effect on the electrolyte concentration in the blood, no water retention (edema) is seen.

Diagnosis and course of the disease

If Schwartz-Bartter syndrome is suspected, various laboratory tests are performed. Hyponatremia with a sodium concentration of less than 135 mmol /l is particularly striking. The osmolality of the serum is decreased overall. It is below 270 mosmol /kg. Due to the increased amount of water in the vascular system, the central venous pressure (CVP) is increased. Central venous pressure (CVP) is the blood pressure prevailing in the right atrium and superior vena cava. It is measured invasively through a central venous catheter (CVC) and determined with a manometer. Edema or abdominal dropsy are not detectable. On the other hand, a low urine volume is noticeable. Urine osmolality and specific gravity are inappropriately elevated. The sodium concentration is also much too high with values above 20 mmol per liter. Determination of ADH levels in the blood has not been shown to be useful. In Schwartz-Bartter syndrome, levels can be both elevated and normal. Thus, an elevated blood ADH level is not a necessary criterion for the diagnosis of Schwartz-Bartter syndrome.Based on osmolality values and urine volume, Schwartz-Bartter syndrome can be differentiated from other urinary concentration disorders such as diabetes insipidus centralis or diabetes insipidus renalis.

Complications

Schwartz-Bartter syndrome does not necessarily cause symptoms or lead to complications in every case. In some rare cases, the syndrome progresses completely without symptoms. In other cases, however, affected individuals suffer from severe headaches and continued loss of appetite. There is a loss of weight and often dehydration. Vomiting or nausea can also occur due to the disease and have a very negative effect on the daily life of the affected person. Most patients also suffer from a change in personality, which can lead to psychological complaints or depression and social difficulties. The disorders of consciousness can also lead to coma or delirium. Frequently, epileptic seizures also occur, which in the worst case can lead to the death of the affected person. The patient’s reflexes are also significantly weakened due to Schwartz-Bartter syndrome. Treatment of Schwartz-Bartter syndrome is usually symptomatic. The affected person must take a solution to restore the electrolyte balance. Further symptoms are treated with medication. Whether there is a decreased life expectancy of the patient cannot be generally predicted.

When should you see a doctor?

With Schwartz-Bartter syndrome, a visit to a physician is definitely necessary. In this disease, there can be no independent cure and the symptoms usually worsen if no treatment is initiated. However, early diagnosis with early treatment has a very positive effect on the course of the disease and can prevent further complications. A doctor should be consulted in Schwartz-Bartter syndrome if the patient suffers from severe headache, which is also associated with nausea and vomiting. In many cases, a sudden loss of appetite may also indicate Schwartz-Bartter syndrome and must also be evaluated by a physician. Most affected individuals also show changes in their personality or severe disturbances in consciousness, and loss of consciousness may occur. Epileptic seizures may also be indicative of Schwartz-Bartter syndrome. In the first instance, a general practitioner may be consulted for Schwartz-Bartter syndrome. However, further treatment is usually provided by a specialist, and the subsequent course cannot be universally predicted.

Treatment and therapy

Therapy depends first on the clinical symptoms and second on the cause of Schwartz-Bartter syndrome. If the diagnosis is an asymptomatic incidental finding, restriction of drinking may already be sufficient as therapy. However, if neurological symptoms occur, medical treatment is required. Usually, slow infusions of hypertonic (10-percent) or isotonic (0.9-percent) saline are given. This is to compensate for the sodium deficiency. The sodium concentration in the blood should be raised only slowly. Raising the concentration too quickly can lead to central pontine myelinolysis. This is a neurological disorder in which the sheathing of nerve fibers in the brainstem area is damaged. The first symptoms of this disease appear half a week after substitution. There are disturbances of consciousness, coma, increasing paralysis and difficulty in swallowing. Although the majority of patients recover from these symptoms, a fatal outcome is possible. In therapy, it is important to remember that hyponatremia is often accompanied by hypokalemia. Thus, substitution of potassium also has a positive effect on the treatment of hyponatremia. Vaptans represent a newer therapeutic option. Vaptans are vasopressin antagonists. They block the action of antidiuretic hormone in the kidney. In addition, the incorporation of the so-called aquaporins into the collecting tubes of the kidney is prevented. This promotes the excretion of electrolyte-free water. Tolvaptan is the only vasopressin antagonist approved in Germany.

Prevention

Because other diseases usually underlie Schwartz-Bartter syndrome, targeted prevention is not possible.

Aftercare

Since Schwartz-Bartter syndrome is a congenital and thus also genetically determined disease, it can usually not come to an independent cure, so that the affected person is always dependent on the examination and treatment by a doctor. Measures and options for aftercare are also usually significantly limited, whereby first and foremost a rapid diagnosis should be made in order to prevent the occurrence of further complaints and complications. Should the affected person or the parents wish to have children, first and foremost a genetic examination and counseling should be performed in order to prevent the recurrence of this disease. In most cases, Schwartz-Bartter syndrome can be well alleviated by the measures of physiotherapy or physical therapy. In doing so, sufferers can perform many of the exercises in the comfort of their own homes to prevent further discomfort from occurring and to speed healing. Most sufferers of Schwartz-Bartter syndrome also rely on taking medication. All instructions from the doctor should be followed. Likewise, attention should be paid to the prescribed dosage and regular intake.

Follow-up

Since Schwartz-Bartter syndrome is a congenital and thus also genetically determined disease, it can thereby usually not come to an independent cure, so that the affected person is thereby always dependent on the examination and treatment by a doctor. In this context, the measures and the possibilities of aftercare are usually also significantly limited. First and foremost, a quick diagnosis should be made in order to prevent the occurrence of further complaints and complications. If affected individuals wish to have children, genetic testing and counseling is recommended to prevent recurrence of the disease. In most cases, Schwartz-Bartter syndrome can be well alleviated by the measures of physical therapy or physiotherapy. In doing so, the sufferer can also perform many of the exercises in the comfort of their own home to prevent the onset of other symptoms and speed healing. Most sufferers of Schwartz-Bartter syndrome are also dependent on taking medication. All doctor’s instructions should be followed, and a doctor should be consulted first if there are any questions or if anything is unclear. Likewise, the correct dosage and also regular intake should be observed.

This is what you can do yourself

Patients suffering from Schwartz-Bartter syndrome should pay attention to the amount they drink, among other things. Depending on the exact diagnosis, it may already help if they drink less fluid. In connection with neurological symptoms, however, those affected should consult a doctor to prevent a sodium deficiency or similar problems. In close consultation with the attending physician, the sodium deficiency can be gradually compensated. Good body awareness is very important to detect any health disorders in time. That is why patients should observe themselves. Headaches, lethargy or irritability and nausea may indicate aggravation. Muscular weakness and cramps are also possible. To counteract the sodium deficiency, a change in diet is usually not enough. That’s why it’s important for sufferers to follow the doctor’s exact instructions. Disturbances of consciousness or confused states should not be concealed, because otherwise there is a risk that the seizures will worsen. It is better to take targeted action against the symptoms and to interpret one’s own body signals correctly. Since the disease is rare, there are hardly any self-help groups. This makes trust between patient and doctor all the more important.