Many also show joint and muscle tone abnormalities, including hypotonia and joint looseness in the hips. Skeletal problems may also be present, including abnormal curvatures of the spine. An informal study conducted by Tetrasomy & Pentasomy X Syndrome Information and Support found that 10% of girls had joint laxity in the hips and 20% had joint limitations in a sample size of 20 tetrasomy and pentasomy patients.