Rett syndrome is a rare neurodevelopmental disorder that affects approximately one in 10,000 to 23,000 female births. More than 200 mutations in the MECP2 gene have been attributed to improper brain development in Rett syndrome.
The disease is broadly classified into two types: classical Rett syndrome and atypical Rett syndrome, in which the symptoms do not meet all diagnostic criteria. Atypical Rett is further divided into subtypes based on symptoms and causative mutation, which can sometimes affect genes other than MECP2. One such atypical Rett syndrome subtype is the late childhood regression variant.

Causes

Similar to classical Rett syndrome, the late childhood regression type is caused by mutations in the MECP2 gene. Three mutations that can lead to late childhood regression have been identified:

  1. A point mutation that causes a change in the amino acid sequence (building blocks of proteins) from arginine to cysteine at position 306 in the MeCP2 protein (p.R306C)
  2. A point mutation that causes a change in the amino acid sequence from arginine to cysteine at position 133 in the MeCP2 protein (p.R133C)
  3. A nonsense mutation that causes the MeCP2 protein to be truncated or shorter than normal (p.R294X)

Diagnosis

Genetic testing for these three mutations can help in the early diagnosis of the disease and in planning for suitable treatment options.

Symptoms

In classical Rett syndrome, symptoms such as small head circumference (microcephaly) and motor problems are seen right from age three months with progressive worsening usually up to age 10. In the late childhood regression type, children start showing regression in language and motor skills much later in childhood (usually at age 36 months) and have a normal head circumference.

The symptoms of late childhood regression also are comparatively milder than classical Rett syndrome. Children, especially those with the p.R133C mutation, would likely have learned to sit, walk, and even use words before the diagnosis is confirmed.

Treatment options

Treatment for the late childhood regression variant is symptomatic and supportive. Physical and occupational therapy might help improve walking ability and everyday activities.

Since speech is not affected much in late childhood regression type, extensive speech therapy might not be required. However, it may still be helpful to consult with a speech and language pathologist (SLP) to further improve the patient’s speaking and swallowing abilities.

Nutrition goals and recommended feeding strategies to tackle dietary inadequacy need to be met, as motor problems can impair feeding. If seizures are observed, a ketogenic diet and anti-epileptic drugs might be required.

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