Water Intoxication in PWS

Due to medical crisis where a young person with PWS ended up in intensive care with a possible diagnosis of water intoxication, we have asked our medical boards about the situation and the following is a compilation from their responses.

Water intoxication is well known to occur in children and adults with eating disorders regardless of mental abilities, and also in individuals who are severely retarded. This is not a new phenomenon.  The problem of water intoxication is a difficult one and may be related to two different physiological mechanisms: some of the patients we have seen have compulsive water drinking and often need to be restricted and / or monitored in order to keep their electrolytes in balance; this seems to be a problem related to the PWS itself. 

On the other hand there is a syndrome called SIADH (Syndrome of Inappropriate Antidiruetic Hormone Hypersecretion) which is related to a problem the kidney has in filtering out the excretions and in this case the kidney absorbs too much water. This problem may be related to medications, may occur with other psychiatric maladies and may occur unrelated to all of these. The latter problem is much more likely to throw the electrolytes out of order, as the body usually seems designed to handle fluids without throwing electrolytes off. However with the person with PWS, this may be more complicated because of right heart failure, and decidedly needs to be reviewed and handled by a pediatrician/internist.

In SIADH, there is an inappropriate release of anti-diuretic hormone that causes water retention and can cause a severe hyponatremia (metabolic condition in which there is not enough sodium (salt) in the body fluids outside the cells).  What medications the individual is on, or if there were other medical issues, may make a difference for the diagnosis of water intoxication. Although this is not a common happening in PWS, it pays to be aware that it has happened in a few cases. 

Symptoms of hyponatremia include: Common symptoms include: 

Abnormal mental status:

• Confusion
• Decreased consciousness
• Hallucinations
• Possible coma
• Convulsions
• Fatigue
• Headache
• Irritability
• Loss of appetite
• Muscle spasms or cramps
• Muscle weakness
• Nausea
• Restlessness
• Vomiting

A further study done on 45 individuals with PWS also found: " In 45 the clinical PWS diagnosis was confirmed by molecular (genetic) testing: nine of them with a confirmed PWS diagnosis had a deletion of chromosome 15q11-13, in nine individuals no deletion was identified. The majority of individuals who increased their water consumption to extreme values belonged to the non-deletion group. Two in the non-deletion group developed hyponatraemia while receiving psychiatric medication."

Treatment seems to be by administering desmopressin  (a hormone used to reduce urine production) either orally, or nasally.

Physicians, see also: 

Water intoxication in a patient with the Prader-Willi syndrome treated with desmopressin for nocturnal enuresis.