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Ministry of National Guard – Health Affairs, Riyadh, Saudi Arabia
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Department of Paediatrics, Endocrine Division, Jeddah, Saudi Arabia
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Ministry of National Guard – Health Affairs, Riyadh, Saudi Arabia
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Ministry of National Guard – Health Affairs, Riyadh, Saudi Arabia
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Faculty of medicine, Sohag University, Egypt
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Summary
X-linked hypophosphatemic rickets (XLH), the most prevalent form of inherited hypophosphatemic rickets, is caused by loss-of-function mutations in the gene encoding phosphate-regulating endopeptidase homolog, X-linked (PHEX). This case series presents 14 cases of XLH from Gulf Cooperation Council (GCC) countries. The patients’ medical history, biochemical and radiological investigative findings, as well as treatment responses and side effects from both conventional and burosumab therapy, are described. Cases were aged 2–40 years at diagnosis. There were two male cases and 12 female cases. All cases were treated with conventional therapy which resulted in a lack of improvement in or worsening of the clinical signs and symptoms of rickets or biochemical parameters. Side effects of conventional therapy included nausea, diarrhea, abdominal pain, nephrocalcinosis, and hyperparathyroidism, which affected the patients’ quality of life and adherence to treatment. In the 10 patients treated with burosumab, there was a marked improvement in the biochemical markers of rickets, with a mean increase in serum phosphate of +0.56 mmol/L and tubular maximum phosphate reabsorption (TmP) to glomerular filtration rate (GFR) ratio (TmP/GFR) of +0.39 mmol/L at 12 months compared to baseline. Furthermore, a mean decrease in serum alkaline phosphatase (ALP) of −80.80 IU/L and parathyroid hormone (PTH) of −63.61 pmol/L at 12 months compared to baseline was observed in these patients. Additionally, patients treated with burosumab reported reduced pain, muscle weakness, and fatigue as well as the ability to lead more physically active lives with no significant side effects of treatment.
Learning points
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Conventional therapy resulted in a suboptimal response, with a lack of improvement of clinical signs and symptoms.
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Side effects of conventional therapy included nausea, diarrhea, abdominal pain, nephrocalcinosis, and hyperparathyroidism, which affected the patients’ quality of life and adherence to treatment.
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Burosumab demonstrated marked improvements in the biochemical markers of rickets, in addition to reducing pain, muscle weakness, and fatigue.
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There were no significant side effects associated with burosumab therapy.
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Summary
3-M syndrome is a rare autosomal recessive disorder caused by mutations in the CUL7, OBSL1 and CCDC8 genes. It is characterised by growth failure, dysmorphic features and skeletal abnormalities. Data in the literature show variable efficacy of GH in the treatment of short stature. We report four Emirati siblings with the condition. The index case is a 10-year-old boy with characteristic features, including prenatal and postnatal growth failure, a triangular face, a long philtrum, full lips and prominent heels. Genetic testing confirmed a novel mutation (p.val88Ala) in the CUL7 gene. The parents are healthy, first-degree cousins with nine children, of whom two died in the first year of life with respiratory failure. Both had low birth weight and growth retardation. The boy's older sibling reached an adult height of 117 cm (−6.71 SDS). She was never treated with GH. He was started on GH treatment at 7 years of age, when his height was 94 cm (−5.3 SDS). 3-M syndrome should be considered in children with short stature who have associated dysmorphism and skeletal abnormalities. The diagnosis is more likely to occur in families that have a history of consanguinity and more than one affected sibling. Death in early infancy due to respiratory failure is another clue to the diagnosis, which might have a variable phenotype within a family. Genetic testing is important for confirming the diagnosis and for genetic counselling. GH treatment might be beneficial in improving stature in affected children.
Learning points
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3-M syndrome should be considered in families that have more than one sibling with short stature, particularly if there is consanguinity.
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Syndrome phenotype might be variable within a family with the same mutation.
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Genetic analysis is helpful in confirming diagnosis in the presence of variable siblings' phenotype.
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GH treatment might be useful in improving stature in 3-M syndrome.
