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

• Conventional therapy resulted in a suboptimal response, with a lack of improvement of clinical signs and symptoms.

• Side effects of conventional therapy included nausea, diarrhea, abdominal pain, nephrocalcinosis, and hyperparathyroidism, which affected the patients’ quality of life and adherence to treatment.

• Burosumab demonstrated marked improvements in the biochemical markers of rickets, in addition to reducing pain, muscle weakness, and fatigue.

• There were no significant side effects associated with burosumab therapy.

Summary

A 73-year-old woman with type 2 diabetes mellitus was referred to our department for glycaemic control. Physical examination revealed two subcutaneous hard masses around the left shoulder and the right hip joint. The patient could not fully extend her fingers because of skin sclerosis in both hands. Laboratory studies showed hyperphosphataemia and a high ratio of renal tubular maximum reabsorption of phosphate to glomerular filtration rate. There were no abnormalities in serum calcium, creatinine, alkaline phosphatase, and intact parathyroid hormone levels, whereas serum fibroblast growth factor 23 was low. Hyperphosphataemic familial tumoural calcinosis/hyperostosis-hyperphosphataemia syndrome (HFTC/HHS) was diagnosed using whole genome sequencing that revealed a novel frameshift beyond the 584th threonine located in the lectin domain of UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 associated with a duplication of the 1748th thymine in the coding region of the corresponding gene. Furthermore, anti-nuclear, anti-centromere, and anti-cardiolipin antibodies were positive, implying that comorbid limited type scleroderma might play a role in tumoural calcinosis (TC) development. A low phosphate diet was prescribed with phosphate-lowering medications, including aluminium hydroxide, acetazolamide, and sevelamer hydrochloride. The patient displayed a decrease in serum phosphate levels from 6.5 to 5.5 mg/dL 10 months after the initiation of treatment, but her TC had not improved during treatment for more than 1 year. This case was interesting because the patient with HFTC/HHS exhibited TC despite being over her 60s, and subsequent scleroderma might contribute to the specific clinical course. When HFTC/HHS presents with elderly-onset TC, the involvement of comorbidities in exacerbating TC should be considered.

Learning points

• HFTC/HHS occurs on an autosomal recessive basis, but its clinical course and manifestations differ significantly throughout the cases.

• HFTC/HHS may be undiagnosed until later in life because of its rarity, unfamiliarity, and phenotype diversity; therefore, HFTC/HHS should be included in the differential diagnosis of elderly patients with unexplained hyperphosphataemia or ectopic calcinosis.

• Comorbidities, including rheumatologic disorders, may contribute to developing HFTC/HHS-associated calcinosis.

Summary

Primary hyperparathyroidism (PHPT) is a common endocrinological pathology; nonetheless, it is rarely diagnosed in pregnancy. Primary hyperparathyroidism can present with clinically expressed hypercalcemia. High Ca levels in the blood may lead to a miscarriage. We present the case of a 39-year-old woman who visited our Endocrinology clinic in search of a cause of infertility. Blood work showed elevated Ca and parathyroid hormone (PTH) levels. Upper left parathyroid gland adenoma was found during a neck ultrasound. Parathyroid gland adenoma was likely the cause of PHPT and was treated with parathyroidectomy. Surgery was carried out, and the upper left parathyroid lobe adenoma was removed. High levels of Ca were found in all performed blood works since the first visit to the clinic, but following the surgery, Ca levels of the patient were in the normal range and the woman got pregnant for the third time, later delivering a healthy baby. In conclusion, we would like to put forward the idea that an evaluation of Ca level in the blood should be included in the protocol for treating patients with recurrent miscarriages. Early detection of hypercalcemia can improve the outcomes of disease that primary hyperparathyroidism can cause. Swift and accurate decrease of serum Ca correspondingly safeguards the woman from a possible pregnancy loss along with complications that arise from it.–

Learning points

• Primary hyperparathyroidism (PHPT) is a common endocrinological pathology, nonetheless, it is rarely diagnosed in pregnancy.

• Primary hyperparathyroidism can present with clinically expressed hypercalcemia, and high Ca levels in the blood may lead to a miscarriage.

• Early detection of hypercalcemia can improve the outcomes of disease that primary hyperparathyroidism can cause.

• Swift and accurate decrease of serum Ca correspondingly safeguards the woman from a possible pregnancy loss along with complications that arise from it.

• All pregnant patients with hypercalcemia should be assessed for the presence of primary hyperparathyroidism as it is likely the cause.

Summary

A 44-year-old athletic man presented in 2009 with severe low back pain. Dual-energy x-ray absorptiometry revealed severe osteoporosis; serum testosterone was 189 ng/dL while serum estradiol (E₂) measured by liquid chromatography/mass spectrometry was 8 pg/mL. DNA was extracted and sequenced from a blood sample from the patient since his maternal first cousin also had low bone mass and both patients were screened for aromatase dysfunction by PCR analysis for the CYP19A1 gene, which encodes aromatase. No known pathologic mutations were observed in the coding exons, but novel single nucleotide polymorphisms were detected both in the proband and in his cousin. Treatment with topical testosterone started in August 2010. Over the next 8 years, testosterone dosage was varied and switched from topical gel to injections and maintained on depo-injections of testosterone at about 60 mg once per week. Re-examination in March 2012 included a brain MRI to exclude pituitary lesions; hyperparathyroidism was ruled out (normal serum parathyroid hormone, calcium, and calcium to phosphorous ratio) and celiac disease was excluded (negative transglutaminase antibodies). Follow-up in October 2018 showed improved bone mineral density of the lumbar spine by 29% and of the left femoral hip by 15% compared to baseline measurements. This reveals the importance of measuring serum E₂ for making the correct diagnosis, as well as for monitoring a therapeutic effect. Herein, we propose treatment of male osteoporosis where serum E₂ levels are below about 20 pg/mL with testosterone to reverse osteoporosis.

Learning points

• Estrogen deficiency in the diagnosis of male idiopathic osteoporosis.

• Importance of serum estradiol in male osteoporosis.

• Role of polymorphisms in aromatase gene on bone health.

• Reversal of osteoporosis.

• Tailored testosterone treatment for bone health.

Summary

We report the case of a 69-year-old female with systemic mastocytosis, diagnosed based on widespread pigmented papules and macules, elevated serum tryptase levels and confirmatory skin and bone marrow biopsy, on a background of osteoporosis. A CT demonstrated multiple sclerotic lesions within lumbar vertebral bodies, sacrum and ileum, with surrounding osteolysis but no obvious compression fractures. She was treated with the RANK-L inhibitor denosumab, resulting in significant bone mineral density gain over the following 5 years. However, her serum tryptase levels gradually increased during this period despite treatment with the multikinase inhibitor, midostaurin. It is thus conceivable that her rapid increase in bone mineral density may be partly contributed by a predominance of pro-osteoblastic mediators released by abnormal mast cells, suggestive of more advanced disease. This case highlights the complexities of systemic mastocytosis-related bone disease and the interplay of numerous mediators contributing to a phenotype of both increased bone resorption and formation.

Learning points

• Systemic mastocytosis is a neoplastic disease of mast cells characterized by abnormal proliferation and accumulation in the skin and other organs. It is most frequently associated with the somatic gain-of-function KIT D816V mutation.

• Systemic mastocytosis should be suspected in patients presenting with not only cutaneous symptoms suggestive of mast cell degranulation such as anaphylaxis, flushing or urticaria but also unexplained osteoporosis and gastrointestinal and constitutional symptoms.

• The prevalence of osteoporosis in systemic mastocytosis is high. Mast cell activation leads to the secretion of numerous chemical mediators which either promote or inhibit osteoclastic and/or osteoblastic activity, with the balance usually in favour of increased bone resorption. However, in advanced diseases with high mast cell burden, mast-cell-derived cytokines and mediators may promote osteoblastic activity, leading to osteosclerosis and apparent increases in bone mineral density.

• Treatment of osteoporosis in systemic mastocytosis involves antiresorptive therapy with bisphosphonates and more recently, denosumab. There are limited data on the role of osteoanabolic agents.

Summary

A 77-year-old female patient with a history of treated breast cancer and a recently diagnosed laryngeal cancer presented with severe hypercalcaemia associated with suppressed parathyroid hormone (PTH) levels. Her initial investigations included 25-hydroxy vitamin D levels, short synacthen test, bone scan, myeloma screen and thyroid function tests which were within normality. A computerised tomography (CT) scan showed some right lung apical fibrotic changes. Her PTH-related peptide (PTHrP) was normal and sarcoidosis was also excluded. Her previous and current malignancies were thought to be unlikely behind her hypercalcaemia. Her 1,25-dihydroxy vitamin D (calcitriol) levels were found to be elevated. Her hypercalcaemia was initially managed with intravenous fluids and intermittent bisphosphonates infusions which would transiently reduce her calcium levels. Steroid treatment was initiated which improved her hypercalcaemia; however, the calcium levels rebounded on tapering the steroids down, a pre-requisite prior to a positron emission computerised tomography (PET-CT) scan to determine the source of the excess calcitriol production. This was cancelled following an emergency admission with marked hypercalcaemia and acute renal and liver injury. A contemporary CT scan showed a right apical lung mass with hepatic lesions suggestive of a disseminated lung primary. The histology obtained from a liver biopsy was compatible with metastatic small-cell lung carcinoma. Unfortunately, her clinical condition deteriorated further and she did not survive. To the best of our knowledge, this is the first report in the literature describing calcitriol-mediated hypercalcaemia due to a small-cell lung cancer.

Learning points

• Paraneoplastic hypercalcaemia may manifest even without overt detection of the primary cancer.

• The workup for paraneoplastic hypercalcaemia should be meticulous.

• Both bisphosphonates and steroids are useful in the initial management of calcitriol-mediated hypercalcaemia, but the definitive management is the treatment of the cause.

Summary

We present the first report of use of recombinant human parathyroid hormone (1-84) (rhPTH(1-84)) in a hypoparathyroid patient during early pregnancy and lactation. The patient developed postoperative hypoparathyroidism as a 28-year-old woman following total thyroidectomy for multinodular goiter. She was not well controlled with conventional therapy, and started rhPTH(1-84) in 2015 following its approval in the United States. She became pregnant in 2018 at age 40. She discontinued rhPTH(1-84) therapy at 5 weeks gestation but resumed in the postpartum period while breastfeeding. Her daughter’s serum calcium was borderline elevated at 8 days postpartum but within the normal range at 8 weeks postpartum. The patient stopped nursing at around 6 months postpartum. Her daughter is now at 4 years and 5 months of age and is healthy and meeting developmental milestones. She was again pregnant at 8 months postpartum from her first pregnancy, and she made an informed decision to continue parathyroid hormone. At 15 weeks gestation, rhPTH(1-84) was recalled in the United States due to issues with the delivery device, and she discontinued rhPTH(1-84) treatment and resumed calcium and calcitriol supplements. She gave birth to a baby boy at 39 weeks in January 2020. At 3 years and 2 months of age, he is overall healthy. Further data are needed regarding the safety of rhPTH(1-84) in pregnancy and lactation.

Learning points

• rhPTH(1-84) is approved for therapy of patients with hypoparathyroidism; however, there are no data regarding the safety of treatment during nursing and pregnancy.

• There are multiple alterations in mineral metabolism during normal pregnancy and lactation.

Summary

We present an adolescent with X-linked hypophosphatemic rickets (XLH) with bone age advancement and its response to aromatase inhibitors (AIs). A male with XLH, confirmed with a deletion on the PHEX gene, received regular treatment since the first year of life with average growth velocity and height. He had bone age compatible with chronological age until 13 when he had a bone age advancement and a decrease in the predicted final height thought to be due to initiation of oral isotretinoin, which has been previously reported. Then, anastrozole was initiated and maintained concomitant to the rickets treatment for 2 years with bone age stabilization. He had no adverse effects or worsening of bone health markers. As a result, he maintained his height gain and improved his final height Z score compared with the predicted final height at initiating anastrozole. In conclusion, although AIs was a reasonable strategy to stabilize bone age and minimize height impairment, careful monitoring is mandatory to understand its benefits and effects on XLH patients.

Learning points

• Although X-linked hypophosphatemic rickets patients have normal puberty, they can be affected by metabolic and environmental factors that may advance their bone age and impair the predicted final height, similar to the general population.

• Isotretinoin may accelerate skeletal maturation during puberty in an adolescent with X-linked hypophosphatemic rickets.

• Aromatase inhibitors showed to be a reasonable strategy to stabilize bone age and minimize height impairment in an adolescent with X-linked hypophosphatemic rickets.

Summary

Hypercalcemia due to parathyroid carcinoma (PC) is safely and quickly controlled with rapidly increasing evocalcet doses. Most parathyroid carcinomas are detected because of hypercalcemia due to primary hyperparathyroidism (PHPT). Hypercalcemia becomes more severe in patients with PC than those with parathyroid adenoma or hyperplasia. Hypercalcemia often causes renal dysfunction, gastrointestinal symptoms, and psychiatric symptoms. Consequently, the serum calcium level needs to be promptly corrected. Here, we report a case of PC with remarkably persistent hypercalcemia, which we safely and quickly controlled with rapidly increasing evocalcet doses. A 77-year-old female presented with renal dysfunction. Her serum calcium (Ca) and intact parathyroid hormone serum levels were 13.9 mg/dL and 1.074 pg/mL, respectively. Her renal function worsened because of hypercalcemia due to PHPT. Technetium-99 m methoxy-isobutyl-isonitrile parathyroid scintigraphic examination revealed an accumulation below the right thyroid lobe. CT examination showed a 35-mm mass. Hypercalcemia needed to be immediately corrected because of the patient’s worsening renal function. Evocalcet treatment at a gradually increasing dose of up to 20 mg over 3 weeks allowed her serum Ca level to be maintained below 11 mg/dL. Only mild nausea was observed at the beginning of the treatment. The mass was suspected as PC because the hypercalcemia was refractory to high-dose evocalcet. The patient was treated with parathyroidectomy and ipsilateral thyroidectomy. PC was diagnosed based on the pathological findings of capsular and venous invasion. The patient’s renal function improved and surgery could be safely performed by promptly correcting hypercalcemia.

Learning points

• Hypercalcemia due to parathyroid carcinoma (PC) is often more severe than that caused by parathyroid adenoma or hyperplasia.

• PC is a rare disease, but it should be considered if the patient has intractable hypercalcemia due to primary hyperparathyroidism (PHPT).

• Evocalcet, which is used to treat hypercalcemia due to PHPT, does not interact with P450 (CYP) and causes few side effects.

• Complications, including renal dysfunction, were improved and the surgery could be safely performed by promptly correcting hypercalcemia.

• PC has a high recurrence rate. En-block excision is necessary when PC is suspected.

Summary

Tenofovir-induced osteomalacia secondary to proximal renal tubular dysfunction is not an uncommon complication known to occur. A 46-year-old woman was referred for the evaluation of osteoporosis which was diagnosed elsewhere. She had polyarthralgia, bony pains and proximal muscle weakness of 1 year duration. She was diagnosed to have HIV infection and was on antiretroviral therapy that consisted of tenofovir, lamivudine and efavirenz for the past 12 years. She had attained menopause 5 years back. On examination, she had bone tenderness, proximal myopathy and painful restriction of movement of her lower limbs. Investigations showed features of renal tubular acidosis, hypophosphatemia and raised alkaline phosphatase that were suggestive of osteomalacia. X-ray of the pelvis showed diffuse osteopenia and an MRI of the pelvis done showed multiple insufficiency fractures involving the head of femur on both sides. Following this, her tenofovir-based regimen was changed to abacavir, efavirenz and lamivudine with addition of neutral phosphate supplements and calcitriol. On follow-up after 6 months, she had significant improvement in her symptoms as well as in the bone mineral density at the lumbar spine (33.2%), femoral neck (27.6%), trabecular bone score (13.2%) and reduction in the buckling ratio at the narrow neck (6.3%), inter-trochanteric region (34%) and femoral shaft (28.8%). Tenofovir-induced osteomalacia is encountered in individuals on prolonged treatment with tenofovir. Treatment consists of changing to a non-tenofovir-based regimen, as well as supplementation of phosphate and calcitriol. Treatment results in remarkable improvement in symptoms and most densitometric indices.

Learning points

• Tenofovir is a nucleotide reverse transcriptase inhibitor (NRTI) and is a major drug in the treatment of retroviral and hepatitis B infections.

• Tenofovir-related hypophosphatemic osteomalacia is related to proximal tubulopathy and is not an uncommon occurrence.

• Treatment mandates changing to a non-tenofovir-based regimen with supplementation of neutral phosphate and calcitriol.

• Treatment results in a significant improvement in bone mineral density, trabecular bone score and hip geometric parameters.