Growth of head circumference was measured in 99 RS girls and compared to gross motor function. The degree of head growth deceleration correlated to the severity of gross motor disability at 12 years of age.
Mutations in the MECP2 gene are known to be associated with Rett Syndrome (RTT) in the large majority of sporadic cases. Four Swedish families with a total of eight RTT patients (two in each family), were screened and found negative for MECP2 mutations. The series included females with both classical and forme fruste phenotypes. Rett syndrome thus might still be complex and genetically multifactorial.
The longitudinal development of head growth was investigated in girls with Rett syndrome. Measurements were taken retrospectively from different kinds of records. Growth retardation was expressed in standard deviation (SD) scores. In classic types, the mean head circumference fell successively to 2 SD scores below the norm at the age of 4 y. After the age of 8 y it stabilized close to –3 SD scores. The degree of deceleration correlated strongly to the age at which a deceleration of 1 SD score had occurred. In forme fruste variants, the mean head circumference was within normal limits; however, it was significantly below the norm (–0.8 SD scores). Body height deviated to –2 SD scores at the age of 6 y and was highly correlated to decline in head growth. When head growth was related to the severity of motor disability, there was a continuum from almost normal head growth with well‐preserved gross motor function and some preserved fine motor function to a marked deceleration in head growth with maximum gross and fine motor disability.
