Hypermobility syndrome, also referred to as benign joint hypermobility syndrome is a rare hereditary connective tissue disorder seen in the pediatric age group. Its clinical manifestations are highly variable but the most common features are a chronic pain with hypermobile (hyperlaxity of) joints, hyperextensible skin, fragile tissues which bleed easily, and other extra-musculoskeletal signs.
Hypermobility syndrome (HM) or benign joint hypermobility syndrome (BJHS) is a hereditary connective tissue disorder seen in the pediatric age group. Some authors have defined joint hypermobility syndrome (JHS) as a condition which includes individuals with hypermobile joints accompanied by symptoms of unknown etiology   . Other authors state that hereditary connective tissue disorders may be associated with JHS and "benign JHS" are used to differentiate it from other more life-threatening connective tissue disorders like Ehlers Danlos syndrome (EDS), Marfan syndrome, and Loeys Dietz syndrome . According to Simpson , JHS is currently considered an inherited connective tissue disorder with features similar to those of Marfan syndrome and Ehlers Danlos syndrome type 3, hypermobility type.
Hypermobility syndrome is transmitted in an autosomal pattern. The penetrance is variable  with a majority of the patients having no identifiable collagen protein abnormalities although a few may have a deficiency of tenascin-X . There is often a family history of the syndrome.
Although symptoms can start at any age, they are typically noticed in childhood and adolescence. Females are affected more than males. The presenting complaint is usually severe, debilitating pain, which is aggravated by activity e.g pain in the lower limbs while walking or difficulty writing in school. Children report "cracking" joints, swelling in the joints (especially knees and ankles) lasting for several days, recurrent joint subluxations or dislocations which reduce spontaneously. Exercise, excessive movement and joint stress are believed to cause the chronic joint pain. A backache is another common symptom, especially in the lumbar region as it is the most mobile part of the vertebral column. Other common symptoms include myalgia, cramps, and stiffness of the joints . Affected patients claim to be double jointed and can voluntarily subluxate.
The condition is often misdiagnosed as young children normally have an extensive range of motion at all their joints. The "Beighton score" has been used to diagnose hypermobility but the scores are variable depending on investigators. So currently the Villefranche classification  which includes clinical signs, family history, major and minor criteria is used for diagnosis. The major criteria are joint hyperlaxity, skin hyperextensibility, and no evidence of skin or soft tissue fragility. The minor criteria are a family history of the syndrome, recurrent joint instability, and the ability to bruise easily. Limitation of the Villefranche classification is that it does not account for extra-musculoskeletal manifestations.
The workup depends upon a detailed patient history, family history of joint hypermobility syndrome and thorough physical examination to look for hypermobile joints and signs of tissue fragility. Genetic testing may be useful in the diagnosis of the syndrome. Radiograph findings include small calcifications in the subcutaneous tissues. Magnetic resonance imaging can help to detect white matter lesions .
As gene mutations have not been identified as yet, prenatal testing cannot be recommended. However genetic counseling should be considered if there is a family history.