A 17-year-old girl with Rett syndrome, who was taking no other medicat
ions, was treated with L-carnitine (50 mg/kg/day). Within 2 months of
initiation of treatment, she became much more alert, developed good ey
e contact, started reaching for objects with both hands, and answered
simple questions with one or two words. L-carnitine was discontinued a
nd within 1 week she lapsed into her pretreatment condition of letharg
y with no interest in her environment, not reaching for objects, poor
eye contact, and not speaking. One week after L-carnitine was resumed,
she again became alert, started reaching for objects, and saying one
or two words. Her serum carnitine levels (free and total) were within
normal limits before and after L-carnitine treatment, but were higher
while she was taking L-carnitine. Her serum ammonia was within normal
limits prior to starting L-carnitine. L-carnitine appears to be an eff
ective treatment for this girl with advanced Rett syndrome.