Chromosome affected: Xp22.2
Gene mutation: RSK2
Inheritance: X-linked, so males are more affected
Clinical features in affected males:
(1) severe mental retardation
(2) short, fleshy hands
(3) hyperextensible, tapering fingers
(4) short stature
(5) microcephaly
(6) dental anomalies
(7) stimulus-induced drop episodes (SIDEs) in which an unexpected stimulus results in collapse without loss of consciousness
(8) kyphoscoliosis and/or vertebral defects
(9) coarse facial features
(9a) downslanting palpebral fissures
(9b) maxillary hypoplasia
(9c) prominent brow
(9d) a short, broad nose
(9e) prominent ears
(9f) open mouth expression
(10) hypotonia
(11) absent speech in males
Clinical features in female carriers:
(1) may be completely normal
(2) may show one or more of the following:
(2a) some degree of mental retardation)
(2b) psychosis
(2c) mild physical changes
