The symptoms of Coffin-Lowry syndrome tend to be more severe in males, although symptoms in affected females can range from none to the same severity seen in males. The characteristic facial features seen in affected males become more easily identifiable in late childhood and adulthood. The face is characterized by a prominent forehead and eyebrows, narrowing of both temples, scarce hair on the scalp, thickened eyebrow ridges, downslanting eyelid slits, wide-set eyes, thickened upper eyelids, a broad nasal bridge with a thick dividing cartilage (septum), thick prominent lips, an open mouth, prominent chin and ears.
Limb abnormalities may include large soft hands with double-jointed thick fingers that taper toward the tips, an unusual prominent transverse crease (hypothenar) and a shortened big toe. In males, the skin is loose and may stretch easily. Many bone abnormalities may also occur such as thickening of facial bones, shortening of the long bones, and pointed or sunken breast bone. Abnormal front-to-back and side-to-side curvature of the spine may also be present (kyphosis and scoliosis) and progresses with age. Affected individuals usually have short stature. A smaller than average head size (microcephaly) and dental abnormalities are common. Hearing loss is sometimes associated with Coffin-Lowry syndrome. In rare cases, Vision loss may occur. Heart problems may be present and can be life threatening.
Affected males may have severe to profound intellectual disability. Intelligence in affected females ranges from normal to profound intellectual disability. Severely affected children may have no speech development.
Some affected individuals experience episodes of brief collapse without loss of consciousness (drop attacks) that occur following an unexpected noise or emotional event.