Growth impairment and limited range of joint motion in children should raise suspicion of an attenuated form of mucopolysaccharidosis: expert opinion

Growth impairment together with bone and joint involvement is common to most patients with mucopolysaccharidosis (MPS) disorders. The genetic basis for these metabolic disorders involves various enzyme deficiencies responsible for the catabolism of glycosaminoglycans (GAGs). The incomplete degradation and subsequent accumulation of GAGs result in progressive tissue damage throughout the body. Bone ossification is particularly affected, with the consequent onset of dysostosis multiplex which is the underlying cause of short stature. Joint manifestations, whether joint contractures (MPS I, II, VI, VII) or hyperlaxity (MPS IV), affect fine motor skills and quality of life. Subtle decreases in growth velocity can begin as early as 2–4 years of age. Pediatricians are in the front line to recognize or suspect MPS. However, given the rarity of the disorders and variable ages of symptom onset depending on disease severity, recognition and diagnostic delays remain a challenge, especially for the attenuated forms. Prompt diagnosis and treatment can prevent irreversible disease outcomes. Conclusion: We present a diagnostic algorithm based on growth velocity decline and bone and joint involvement designed to help pediatricians recognize early manifestations of attenuated forms of MPS. We illustrate the paper with examples of abnormal growth curves and subtle radiographic nuances.