Hypotonia-Cystinuria Syndrome

What else is it called?

  • Cystinuria with mitochondrial disease

Get in touch

Contact our caring team on 08452 412 173 for help and support. Our phone lines open 10am-4pm, Monday to Friday.

Prefer to email? Our email address is contact@metabolicsupportuk.org.

What causes it?

Hypotonia-Cystinuria syndrome [HCS] is a very rare autosomal recessive metabolic condition. To date, there is very little information upon this metabolic disorder due to the limited number of individuals who have been diagnosed with this order, more research is required in this area.

How common is it?

HCS is a very rare metabolic condition which has roughly affected 14 individuals to date worldwide, with no preference over males or females or ethnicities.

What are the signs and symptoms?

HCS onset as early as neonatal and can be diagnosed in infancy. Symptoms may vary from individual to individual.

  • Intellectual disability
  • Neonatal seizures
  • Growth delay
  • Distinct body dysmorphia
  • Growth impairment
  • Infantile hypotonia
  • Global developmental delay
  • Minor facial dysmorphism
  • Ptosis [drooping of the lower eye lid]

How is it diagnosed?

Currently, there is very little information upon diagnosis of this condition, more research is required to assert how this metabolic condition is diagnosed.

Can it be treated?

Treatment recommendation for this very limited due to the limited research into this metabolic condition. Management of this condition may depend upon the specific symptoms experienced per individual.

It has been suggested that infantile hypotonia may respond to treatment with pyridostigmine.

Do my family need to be tested?

Hypotonia-cystinuria syndrome can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.

If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.

If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.

Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited hypotonia- cystinuria syndrome. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own.

If you have previously had a child with MCADD and go on to have further children, their Newborn Screening test should be carried out within 24-48 hours of birth.

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: HAP068].

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