COMPASSIONATE ALLOWANCE INFORMATION

RETT (RTT) SYNDROME

DESCRIPTION

Rett Syndrome, one of the MECP2 gene-related disorders, is a progressive neurologic disease in girls characterized by normal birth and apparently normal psychomotor development during the first six to 18 months of life. The girls then enter a short period of developmental stagnation followed by rapid regression in language and motor skills. The hallmark of the disease is the loss of purposeful hand use and its replacement with repetitive stereotyped hand movements. Screaming fits and inconsolable crying are common by age 18-24 months. Additional characteristics include autistic features, panic-like attacks bruxism, (teeth grinding), episodic apnea and/or hyperpnea, gait ataxia and apraxia, tremors, and acquired microcephaly. After this period of rapid deterioration, the disease becomes relatively stable, though girls will likely develop dystonia and foot and hand deformities as they grow older. Seizures occur in up to 90% of affected females. Females with classic Rett syndrome typically survive into adulthood, but the incidence of sudden, unexplained death (which may be caused by cardiac arrhythmias) is significantly higher than in controls of similar age. Rett Syndrome has also been found in males in rare instances.

ALTERNATE NAMES

MECP2 Related Disorder, RTT, RTS

DIAGNOSTIC TESTING AND CODING

The diagnosis of Rett syndrome rests on clinical diagnostic criteria established for the syndrome and/or molecular testing of the MECP2 gene. Molecular genetic testing identifies MECP2 mutations in approximately 80% of females with Rett syndrome.

TREATMENT

Currently there is no cure for RTT. Management is mainly symptomatic focusing on optimizing the individual’s abilities and providing psychosocial support for the family.

PROGRESSION

Females with Rett syndrome may survive into adulthood, but in a very dependent state. The incidence of sudden, unexplained death is significantly higher than in controls of similar age and may in part be caused by the higher incidence of longer corrected QT intervals, T-wave abnormalities, and reduced heart rate variability.

SUGGESTED PROGRAMMATIC ASSESSMENT*

Suggested MER for Evaluation: Molecular genetic testing with sequence analysis of the MECP2 gene on the X chromosome will identify 80% of individuals with Rett syndrome. Additional clinical findings would show a characteristic decline or loss of previously attained developmental milestones (i.e., normal development for 6-18 months, followed by loss of milestones), a description of characteristic motor findings (repetitive hand movements, toe walking or unsteady, wide-based, stiff-legged gait) and severely impaired expressive language.

Suggested Listings for Evaluation:

DETERMINATION

LISTING

REMARKS

Meets Listing

110.08

All claimants with clinical diagnostic criteria of Rett syndrome and abnormal molecular genetic testing of the MECP2 gene. (Positive genetic testing alone would not meet 110.08B).

111.17 or 11.17

112.02 or 12.02

Mental dysfunction meeting the severity of these listings.

Medical Equals

* Adjudicators may, at their discretion, use the Medical Evidence of Record or Listings suggested to evaluate the claim. However, the decision to allow or deny the claim rests with the adjudicator.