Benign joint hypermobility syndrome (BJHS)
Children with hypermobile joints by definition display a range of movement that is considered excessive, taking into consideration the age, gender and ethnic background of the individual. It is estimated that at least 10–15 % of normal children have hypermobile joints and the term joint hypermobility syndrome (JHS) is reserved to the cases of joint hypermobility associated with symptoms with no other causes found for them [4]–[6]. JHS can be associated with hereditary connective tissue disorders, and the term “Benign” is used in contrast to more serious and potentially complicated or life-threatening musculoskeletal syndromes such as some forms of Ehlers-Danlos syndrome (EDS), Marfan syndrome, and Loeys-Dietz syndrome. The prevalence of JHS is not known with precision, given the lack of studies of large cohorts. Sperotto et al., conducted a cross sectional study in a cohort of healthy schoolchildren, aged 8–13 years from the province of Padua, Italy, and found that BJHS occurred in the 13,2 % of the 289 children evaluated [7].
Even if BJHS is very common, this condition is largely under-recognized by primary care physicians and often poorly managed. Symptoms frequently start in childhood and continue into adult life. The pathophysiology of benign joint hypermobility is unclear. Hypermobility is more common in childhood and adolescence, in females, and in some ethnicities, and it tends to lessen during adulthood. Still, polyarticular hypermobility may be present in up to 30 % of males and 40 % of females during early adulthood [8]. For the majority of individuals joint hypermobility may be of no consequence, and what brings a proportion of subjects to develop BJHS is not fully understood. BJHS seems to be transmitted by an autosomal pattern, and first-degree relatives with the disorders can be identified in many cases. Variable penetrance is generally observed [9]. With the exception of a minority of patients, who show a deficiency of tenascin X, no abnormality in collagen or related proteins has been identified as a cause for BJHS [10]. Joint pain is thought to be caused by excessive movement, increasing stress on joint surfaces, ligaments and adjacent structures. Other factors may contribute to the development of the syndrome, such as poor proprioception, autonomic dysfunctions and fatigue secondary to poor sleep [11].
The predominant presenting complaint is pain, which may be widespread and debilitating. The pain typically starts during or after activity. The most common affected sites are the lower limbs after walking (for example walking to and from school). Children usually report excess fatigue, handwriting difficulties or ‘clicking or cracking’ joints. Occasionally episodes of joint swelling lasting hours to days, joint dislocations, or more commonly subluxations with spontaneous reduction are reported. Back-pain is also a common complaint because the lumbar spine is one of the most mobile sections of the vertebral column and the excessive movements may lead to pain in hypermobile subjects. Heavy school bags are often an aggravating feature. Chronic pain results in a reduced exercise tolerance and can negatively impact patients’ life.
A significant proportion of subjects progressively quit sports and other physical activities. In addition, pain amplification is a common feature in these cases [12]. BJHS has been considered to cause only musculoskeletal symptoms for many years, but there is now mounting evidence that many other extra-skeletal manifestations may occur. This symptoms arise usually after the third decade of life, but have been described in adolescents, and may be due to connective tissue abnormalities, linking BJHS and other hereditary disorders of connective tissues, namely Ehlers-Danlos syndrome type III. These include functional and anatomic gastrointestinal tract abnormalities (constipation, bloating, diarrhea, hiatal hernias), autonomic dysfunctions (postural tachycardia syndrome, palpitations, orthostatic intolerance, headache, fatigue) and skin abnormalities (easy bruising, striae) [13], [14]. Some of these symptoms are overlapping with those observed in Juvenile Fibromyalgia (JFM), and indeed there are few reports describing high incidence of BJHS in children with JFM. Furthermore, children who have both JFM and BJHS may exhibit lower tender-points thresholds and a greater number of tender-points compared to children with JFM but no benign joint hypermobility [15].
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