Bone Abstracts

Background: Isotretinoin has demonstrated efficacy in a wide range of disorders. The beneficial effects of the drug, however, are limited by its adverse impact on the bone. Children exposed to high doses are at risk for premature epiphyseal closure, while adults on long-term therapy have an increased tendency to develop hyperostosis and other changes of the bone. Presenting feature and Clinical management A 9-month-old infant presented with vomiting and distended abdomen due to hepatomegaly. CT scan confirmed a left adrenal tumor with multiple liver metastatic lesions and right adrenal mass.Urine VMA/Creatinine was 63.8 umol/mmol (normal < 4.7) and LDH 2333 U/l (normal: 163–452). Ultrasound guided biopsy of liver lesions confirmed a diagnosis of poorly differentiated neuroblastoma. Patient was treated as for high risk neuroblastoma with chemotherapy followed by surgery (bilateral partial adrenalectomy and liver segmentectomies). MRI showed residual liver lesions which was treated with radiation and cis-retinoic acid for 6 months. After 31/2 years patient developed swelling of bilateral lateral malleoli. X-ray of the lower limb showed bilateral widening & cupping of distal tibial metaphysis with reduced bone density and relative shortening of both tibias as compared to fibulas. Bone MRI showed premature fusion with bony bridging affecting central aspect of the growth plate at both distal tibias, affecting 10–15% (left) and 20% (right) of the cross-sectional area of the growth plate. Distal fibular growth plate was open.Patient underwent surgical removal of physeal bar with fat interpositioning between the growth plate and metaphysis and is under monitoring for ‘DISH’ like diffuse skeletal hyperostosis.

Discussion: The effects of retinoids on bone may be profound and include progressive calcification of ligaments and tendon insertions, premature fusion of epiphyses, modelling abnormalities of long bones, and perhaps osteoporosis. Although it has been known since 1933 that vitamin A cause bone abnormalities, the mechanism of this effect has been elusive. Recent work suggests a possible relationship of the retinoids with several cytokines, which results in enhanced maturation of the preosteoclast. The knowledge of these effects, in conjunction with continued surveillance, are necessary for expert management and can ensure many years of efficient treatment with minimal toxicity.

Disclosure: The authors declared no competing interests.