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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.
Theodor-Billroth-Academy®, Munich – Sacramento, CA, Germany, USA
INCORE, International Consortium of Research Excellence of the Theodor-Billroth-Academy®, Germany, USA
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UOC of Endocrinology, Department of Medical Specialties, Azienda Ospedaliero-Universitaria di Modena, Ospedale Civile di Baggiovara, Modena, Italy
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INCORE, International Consortium of Research Excellence of the Theodor-Billroth-Academy®, Germany, USA
Department of Surgery, Carl-Thiem-Klinikum, Cottbus, Germany
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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
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Estrogen deficiency in the diagnosis of male idiopathic osteoporosis.
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Importance of serum estradiol in male osteoporosis.
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Role of polymorphisms in aromatase gene on bone health.
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Reversal of osteoporosis.
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Tailored testosterone treatment for bone health.
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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
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Tenofovir is a nucleotide reverse transcriptase inhibitor (NRTI) and is a major drug in the treatment of retroviral and hepatitis B infections.
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Tenofovir-related hypophosphatemic osteomalacia is related to proximal tubulopathy and is not an uncommon occurrence.
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Treatment mandates changing to a non-tenofovir-based regimen with supplementation of neutral phosphate and calcitriol.
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Treatment results in a significant improvement in bone mineral density, trabecular bone score and hip geometric parameters.
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The University of Sydney Concord Clinical School, Concord NSW, Australia.
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Summary
We present the case of a 60-year-old female who developed repeated atraumatic stress fractures. She was initially diagnosed with osteoporosis based on her dual-energy X-ray absorptiometry (DXA) scan bone mineral density (BMD) T-scores and started on denosumab therapy. Secondary osteoporosis screen revealed abnormal myeloma screen and low serum phosphate levels. It was thought that the patient had multiple myeloma with associated Fanconi-related tubular dysfunction. However, fibroblast growth factor-23 (FGF-23) levels were grossly elevated, making Fanconi syndrome unlikely. The patient was subsequently diagnosed with two separate conditions, namely cardiac amyloid light-chain (AL) amyloidosis and FGF-23-related hypophosphataemia, likely due to tumour-induced osteomalacia. This case highlights the importance of excluding osteomalacia as a cause of low BMD and checking FGF-23 levels in the workup for hypophosphataemia.
Learning Points
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Tumour-induced osteomalacia is a difficult diagnosis as the tumour is often small and slow growing. Imaging may fail to identify a tumour, and treatment therefore consists of calcitriol and phosphate replacement.
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Tumour-induced osteomalacia should be suspected in the adult presenting with new-onset hypophosphataemia, elevated FGF-23 levels and isolated renal phosphate wasting.
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Serum phosphate is not part of the routine chemistry panels. Routinely checking phosphate levels prior to initiating antiresorptive therapy is warranted.
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DXA cannot distinguish low bone mineral density due to osteoporosis from osteomalacia. Antiresorptive therapy should be avoided in osteomalacia due to the risk of clinical and radiographic deterioration.
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Summary
Human T-cell lymphotropic virus-1 (HTLV-1) causes adult T-cell leukemia and lymphoma (ATLL) and is a rare but important cause of hypercalcemia. A 53-year-old male with HTLV-1-associated myelopathy presented with acute on chronic bilateral lower extremity weakness and numbness. Initial blood work revealed hypercalcemia with corrected calcium of 16.2 mg/dL (8.5–11.5) with normal levels of phosphorus and alkaline phosphatase. Workup for hypercalcemia revealed parathyroid hormone (PTH) of 14 pg/mL (10–65), 25 hydroxy vitamin D at 19.6 ng/mL (30–100), 1,25 dihydroxy vitamin D at 6.7 pg/mL (19.9–79.3), thyroid-stimulating hormone of 1.265 μIU/mL (0.5–5), undetectable PTH-related protein (PTHrP) and lactate dehydrogenase of 433 U/L (100–220). The urine calcium creatinine ratio was 0.388. Reverse transcriptase PCR was positive for HTLV-1 and negative for HTLV-2. Peripheral blood flow cytometry and lymph node biopsy confirmed ATLL. He received treatment with fluids, calcitonin and denosumab after which serum calcium levels fell (nadir: 7.7 mg/dL) and then normalized. Humoral hypercalcemia in this setting is mediated by receptor activator of nuclear factor-kappa B ligand (RANKL), PTHrP and other cytokines. PTHrP levels depend on levels of the TAX gene product, cell type and lymphocyte-specific factors. Thus, a low level, like in our patient, does not rule out HTLV-1 infection/ATLL as the cause of hypercalcemia. Hypercalcemia is known to be responsive to monoclonal antibodies against RANKL given the compound’s role in mediating hypercalcemia in these cases.
Learning points
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Human T-cell lymphotropic virus-1 infection and adult T-cell leukemia and lymphoma are associated with high rates of hypercalcemia and hypercalcemic crises.
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Hypercalcemia in these cases is mediated by osteoclastic bone resorption carried out by several agents including receptor activator of nuclear factor-kappa B ligand, parathyroid hormone-related protein (PTHrP), macrophage inflammatory protein 1 alpha, interleukins, etc. A normal PTHRrP does not rule out humoral hypercalcemia of malignancy in this setting, as indicated by this case.
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Hypercalcemia in such settings is highly responsive to monoclonal antibodies against RANKL given the role the ligand plays in resorptive hypercalcemia.
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Summary
Although bisphosphonates (BPs) are mainly used for the treatment of osteoporosis and are generally safe, long-term use and more dosage as utilised in malignant conditions may be associated with the rare adverse event of an atypical femoral fracture (AFF). Occasionally, the risk of developing an AFF persists long after BPs are withdrawn. A 39-year-old woman who underwent chemotherapy and an autologous stem cell transplantation for multiple myeloma presented to us with history of pain in the left thigh. She had received multiple doses of oral and parenteral BPs for about 10 years in view of the underlying myeloma with osteoporosis. Her investigations showed a suppressed CTX of 192 pg/mL, and radiograph of pelvis displayed thickened cortices with beaking of the left femoral shaft, which was suggestive of an AFF. Following discontinuation of BPs, she underwent prophylactic intra-medullary nailing with which her symptoms improved. Five years later, she presented with similar complaints on the right side. Investigations showed that her bone turnover continued to be suppressed with Cross linked C- Telopeptide of type 1 collagen (CTX) of 165 pg/mL and an X-ray done showed AFF on the right side despite being off BPs. A second intra-medullary nailing was done and on follow-up, she has been symptom-free and independent in her daily activities. Discontinuation of BPs may not prevent the incident second AFF and, therefore, thus warranting long-term follow-up.
Learning points
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Regular screening and follow-up of patients who receive long-term bisphosphonate (BP) therapy should be done.
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Discontinuation of BPs does not preclude the possibility of repeated occurrence of a second AFF.
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Long-term BP therapy warrants regular monitoring and follow-up should an AFF occur
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Summary
Milk–alkali syndrome (MAS) is a triad of hypercalcaemia, metabolic alkalosis and renal insufficiency. In this study, we present a case of milk–alkali syndrome secondary to concurrent use of over-the-counter (OTC) calcium carbonate-containing antacid tablets (Rennie®) for dyspepsia and calcium carbonate with vitamin D3 (Adcal D3) for osteoporosis. A 72-year-old woman presented with a 2-day history of nausea, vomiting, epigastric pain, constipation, lethargy and mild delirium. Past medical history included osteoporosis treated with daily Adcal D3. Initial blood tests showed elevated serum-adjusted calcium of 3.77 mmol/L (normal range, 2.2–2.6) and creatinine of 292 µmol/L (45–84) from a baseline of 84. This was corrected with i.v. pamidronate and i.v. fluids. She developed asymptomatic hypocalcaemia and rebound hyperparathyroidism. Myeloma screen, vasculitis screen and serum angiotensin-converting enzyme (ACE) were normal, while the CT of the chest, abdomen and pelvis showed renal stones but no malignancy. A bone marrow biopsy showed no evidence of malignancy. Once the delirium resolved, we established that prior to admission, she had been excessively self-medicating with over-the-counter antacids (Rennie®) as required for epigastric pain. The increasing use of calcium preparations for the management of osteoporosis in addition to easily available OTC dyspepsia preparations has made MAS the third most common cause of hypercalcaemia hospitalisations. Educating patients and healthcare professionals on the risks associated with these seemingly safe medications is required. Appropriate warning labels on both calcium preparations used in the management of osteoporosis and OTC calcium-containing preparations would prevent further similar cases and unnecessary morbidity and hospital admission.
Learning points
What is known?
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An association between high-dose calcium supplementation and hypercalcaemia crisis has been seen in case studies.
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After as little as 1 week of excessive calcium carbonate ingestion, patients can present with symptomatic hypercalcemia, acute renal failure and metabolic alkalosis (1).
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Women aged 50 and younger need 1 g of calcium per day, while aged 51 and older need 1.2 g (1).
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Although the amount of calcium required for MAS is generally thought to be more than 4 g per day, there have been reports at intakes as low as 1.0–1.5 g per day in pre-existing risk factors including renal impairment (2).
What this study adds?
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The danger of excessive ingestion of antacid is not adequately highlighted to prescribers and patients.
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Appropriate warning labels on OTC calcium-containing preparations could prevent unnecessary morbidity and hospital admission.
Department of Endocrinology, The Austin Hospital, Heidelberg, Victoria, Australia
Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
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Department of Endocrinology, Monash Health, Clayton, Victoria, Australia
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Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
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Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
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Women’s Health Research Program, School of Public Health and Preventative Medicine, Monash University, Melbourne, Victoria, Australia
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Summary
Hypophosphatasia (HPP) is a rare and under-recognised genetic defect in bone mineralisation. Patients presenting with fragility fractures may be mistakenly diagnosed as having osteoporosis and prescribed antiresorptive therapy, a treatment which may increase fracture risk. Adult-onset HPPhypophosphatasia was identified in a 40-year-old woman who presented with bilateral atypical femoral fractures after 4 years of denosumab therapy. A low serum alkaline phosphatase (ALP) and increased serum vitamin B6 level signalled the diagnosis, which was later confirmed by identification of two recessive mutations of the ALPL gene. The patient was treated with teriparatide given the unavailability of ALP enzyme-replacement therapy (asfotase alfa). Fracture healing occurred, but impaired mobility persisted. HPP predisposes to atypical femoral fracture (AFF) during antiresorptive therapy; hence, bisphosphonates and denosumab are contraindicated in this condition. Screening patients with fracture or ‘osteoporosis’ to identify a low ALP level is recommended.
Learning points
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Hypophosphatasia (HPP) is a rare and under-recognised cause of bone fragility produced by impaired matrix mineralisation that can be misdiagnosed as a fragility fracture due to age-related bone loss.
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Antiresorptive therapy is contraindicated in HPP.
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Low serum alkaline phosphatase (ALP) provides a clue to the diagnosis.
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Elevated serum vitamin B6 (an ALP substrate) is indicative of HPP, while identification of a mutation in the ALPL gene is confirmatory.
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Enzyme therapy with recombinant ALP (asfotase alfa) is currently prohibitively costly.
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Treatment with anabolic bone agents such as teriparatide has been reported, but whether normally mineralized bone is formed requires further study.
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Summary
Oncogenic osteomalacia secondary to glomus tumor is extremely rare. Localization of causative tumors is critical as surgical resection can lead to a complete biochemical and clinical cure. We present a case of oncogenic osteomalacia treated with resection of glomus tumor. A 39-year-old woman with a history of chronic sinusitis presented with chronic body ache and muscle weakness. Biochemical evaluation revealed elevated alkaline phosphatase hypophosphatemia, increased urinary phosphate excretion, low calcitriol, and FGF23 was unsuppressed suggestive of oncogenic osteomalacia. Diagnostic studies showed increase uptake in multiple bones. Localization with MRI of paranasal sinuses revealed a sinonasal mass with concurrent uptake in the same area on the octreotide scan. Surgical resection of the sinonasal mass was consistent with the glomus tumor. The patient improved both clinically and biochemically postoperatively. Along with the case of oncogenic osteomalacia secondary to a glomus tumor, we have also discussed in detail the recent development in the diagnosis and management of oncogenic osteomalacia.
Learning points
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Tumor-induced osteomalacia is a rare cause of osteomalacia caused by the secretion of FGF23 from mesenchymal tumors.
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Mesenchymal tumors causing TIO are often difficult to localize and treat.
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Resection of the tumor can result in complete resolution of biochemical and clinical manifestations in a very short span of time.
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Glomus tumor can lead to tumor induced osteomalacia and should be surgically treated.
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Summary
Lamin A/C (LMNA) gene mutations cause a heterogeneous group of progeroid disorders, including Hutchinson–Gilford progeria syndrome, mandibuloacral dysplasia, atypical progeroid syndrome (APS) and generalized lipodystrophy-associated progeroid syndrome (GLPS). All of those syndromes are associated with some progeroid features, lipodystrophy and metabolic complications but vary differently depending on a particular mutation and even patients carrying the same gene variant are known to have clinical heterogeneity. We report a new 30-year-old female patient from Russia with an APS and generalized lipodystrophy (GL) due to the heterozygous de novo LMNA p.E262K mutation and compare her clinical and metabolic features to those of other described patients with APS. Despite many health issues, short stature, skeletal problems, GL and late diagnosis of APS, our patient seems to be relatively metabolically healthy for her age when compared to previously described patients with APS.
Learning points
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Atypical progeroid syndromes (APS) are rare and heterogenic with different age of onset and degree of metabolic disorders, which makes this diagnosis very challenging for clinicians and may be missed until the adulthood.
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The clinical picture of the APS depends on a particular mutation in the LMNA gene, but may vary even between the patients with the same mutation.
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The APS due to a heterozygous LMNA p.E262K mutation, which we report in this patient, seems to have association with the generalized lipodystrophy, short stature and osteoporosis, but otherwise, it seems to cause relatively mild metabolic complications by the age of 30.
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The patients with APS and lipodystrophy syndromes require a personalized and multidisciplinary approach, and so they should be referred to highly specialized reference-centres for diagnostics and treatment as early as possible.
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Because of the high heterogeneity of such a rare disease as APS, every patient’s description is noteworthy for a better understanding of this challenging syndrome, including the analysis of genotype-phenotype correlations.
