Most children eventually start speaking, but in cases with severe intellectual disability language use is highly restricted.They have distinctive facial features like:

Small head (microcephaly)
Pointed forehead (trigonocephaly)
Small ears which are low-set
Widely-spaced eyes (hypertelorism)
Droopy eyelids (ptosis)
Broad nasal bridge
Abnormally thin upper lips
Downturned corners of the mouth
Excess skin covering in the inner corner of eyes (epicanthal folds)Some children also experience behavioural problems like distractibility, hyperactivity, impaired communication and social skills, which qualifies them for a diagnosis of ASD and ADHD. Heart defects are very common in children with Jacobsen syndrome. 88.5% of people with the disorder have Paris-Trousseau syndrome, which is a bleeding disorder and causes a lifelong risk of abnormal bleeding and bruising due to dysfunction in the platelets. Other symptoms may include eye problems, ear and sinus infections, hearing problems, bone deformities, growth hormone deficiency, gastrointestinal problems, kidney malfunctions, etc. Cause
Jacobsen syndrome is caused by deletion of genetic material from the long arm of chromosome 11. The size of deletion may vary across patients, but the deletion always occurs at the end terminal of the q arm of chromosome 11. There are three ways in which the deletion could occur:
de novo deletion- this is a random event that occurred during the formation of the sperm or the egg or during the cell division in the embryonic stage, where genes from chromosome 11 get deleted.Imbalanced translocation- in this case, a parent with balanced translocation or other types of chromosomal rearrangement can pass on these genes to their children which further results in an imbalanced translocation.
Some people present with emotional lability and bladder urgency, and occasionally people with PLS experience mild cognitive changes detectable on neuropsychological testing, particularly on measures of executive function.PLS is not considered hereditary when onset is in adulthood; however, juvenile primary lateral sclerosis (JPLS) has been linked to a mutation in the ALS2 gene which encodes the cell-signalling protein alsin.The issue of whether PLS exists as a different entity from ALS is not clear, as some patients initially diagnosed as having PLS ultimately develop lower motor neuron signs. When this happens it is classed as ALS. Spasticity
Primary lateral sclerosis (PLS) usually presents with gradual-onset, progressive, lower-extremity stiffness and pain due to muscle spasticity. Onset is often asymmetrical. Although the muscles do not appear to atrophy as in ALS (at least initially), the disabling aspect of PLS is muscle spasticity and cramping, and intense pain when those muscles are stretched, resulting in joint immobility. A  normal walking stride may become a tiny step shuffle with related instability and falling. Cause
Researchers do not fully understand what causes PLS, although it is thought it could be due to a combination of environmental and genetic factors. Studies are being done to evaluate the possible causes, although linking causality can be difficult due to the relatively low number of people who are diagnosed with PLS.Juvenile PLS may be caused by the ALS2 gene, although this condition is very rare. Diagnosis
There are no specific tests for the diagnosis of PLS.