The authors present the case of a 14 year old man who was admitted as an inpatient to the pediatric ward for back pain. The patient had a three month history of low back pain of moderate intensity with exacerbation periods, so far interpreted as growing pains. The pain had a non-defined pattern, waking the patient at night and worsening after physical activity, making it impossible to perform more intense and prolonged efforts. Had poor response to analgesics and non-steroid anti-inflammatory drugs (NSAIDs). The patient denied other musculoskeletal complaints and mentioned frequent "palpitations", for which he was treated with bisoprolol 2.5 mg/day. He denied other complaints suggesting other organ involvement. He also reported anxiety, panic attacks and learning disability, confirmed by his mother. He had no other relevant medical history. On general physical examination, the patient had lanky biotype, marfanoid habitus (arm span to total height ratio 1.05 (positive when >1.03) and upper segment to lower segment ratio 0.80 (positive when <0.89)), mild arachnodactyly (with positive Steinberg's thumb sign and wrist sign) structural scoliosis with positive Adams test, dorsal kyphosis, lumbar hyperlordosis (Figure 1) and striae on the right dorsal region (Figure 2), without hyperextensible skin. He had active hyperextension of the elbow (20º bilaterally) (Figure 1) and proximal interphalangeal joints and hyperflexion of distal interphalangeal joints (Figure 3). He met GJH criteria, according to the Beighton score (total score of 7 in 9 points-apposition of thumb to flexor aspect of forearm bilateraly, dorsiflexion of fifth metacarpophalangeal joint > 90° bilateraly, hyperextension of the elbow >10° bilateraly and placing flat hands on the floor with straight legs) (Table I). He did not have arthritis or periarticular lesions. There were no suggestive signs of other connective tissue diseases. The patient met the Brighton criteria for JHS (Beighton score ≥4/9, back pain during plus than 3 month, Marfanoid habitus and dorsal unilateral striae) (Table II). The laboratory workup revealed no abnormalities, namely normal inflammatory