Sasigarn A. Bowden

Prevalence of vitamin D deficiency and insufficiency in children with osteopenia or osteoporosis referred to a pediatric metabolic bone clinic.

OBJECTIVES. The purpose of this work was to determine the prevalence of vitamin D deficiency and insufficiency in children with osteopenia or osteoporosis and to evaluate the relationship between serum 25-hydroxyvitamin D levels and bone parameters, including bone mineral density. MATERIALS AND METHODS. Serum 25-hydroxyvitamin D, 1,25 dihydroxyvitamin D, parathyroid hormone, and other bone markers, as well as bone mineral density, were obtained for 85 pediatric patients with primary osteoporosis (caused by osteogenesis imperfecta or juvenile idiopathic osteoporosis) and secondary osteopenia or osteoporosis caused by various underlying chronic illnesses. Pearsons correlation was used to assess the relationship between vitamin D levels and different bone parameters. RESULTS. Vitamin D insufficiency (defined as serum 25-hydroxyvitamin D <30 ng/mL) was observed in 80.0% of patients. Overt vitamin D deficiency (defined as serum 25-hydroxyvitamin D <10 ng/mL) was present in 3.5% of patients. Using a more recent definition for vitamin D deficiency in adults (defined as serum 25-hydroxyvitamin D <20 ng/mL), 21.1% of the patients had vitamin D deficiency. There was a significant inverse correlation between 25-hydroxyvitamin D and parathyroid hormone levels. There was a positive correlation between 1,25 dihydroxyvitamin D and parathyroid hormone, alkaline phosphatase, and urine markers for bone turnover. CONCLUSIONS. Vitamin D insufficiency was remarkably common in pediatric patients with primary and secondary osteopenia or osteoporosis. The inverse relationship between 25-hydroxyvitamin D and parathyroid hormone levels suggests a physiologic impact of insufficient vitamin D levels that may contribute to low bone mass or worsen the primary bone disease. We suggest that monitoring and supplementation of vitamin D should be a priority in the management of pediatric patients with osteopenia or osteoporosis.

Optimizing Bone Health in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle weakness, with eventual loss of ambulation and premature death. The approved therapy with corticosteroids improves muscle strength, prolongs ambulation, and maintains pulmonary function. However, the osteoporotic impact of chronic corticosteroid use further impairs the underlying reduced bone mass seen in DMD, leading to increased fragility fractures of long bones and vertebrae. These serious sequelae adversely affect quality of life and can impact survival. The current clinical issues relating to bone health and bone health screening methods in DMD are presented in this review. Diagnostic studies, including biochemical markers of bone turnover and bone mineral density by dual energy X-ray absorptiometry (DXA), as well as spinal imaging using densitometric lateral spinal imaging, and treatment to optimize bone health in patients with DMD are discussed. Treatment with bisphosphonates offers a method to increase bone mass in these children; oral and intravenous bisphosphonates have been used successfully although treatment is typically reserved for children with fractures and/or bone pain with low bone mass by DXA.

Autosomal Dominant Pseudohypoaldosteronism Type 1 in an Infant with Salt Wasting Crisis Associated with Urinary Tract Infection and Obstructive Uropathy

Type 1 pseudohypoaldosteronism (PHA1) is a salt wasting syndrome caused by renal resistance to aldosterone. Primary renal PHA1 or autosomal dominant PHA1 is caused by mutations in mineralocorticoids receptor gene (NR3C2), while secondary PHA1 is frequently associated with urinary tract infection (UTI) and/or urinary tract malformations (UTM). We report a 14-day-old male infant presenting with severe hyperkalemia, hyponatremic dehydration, metabolic acidosis, and markedly elevated serum aldosterone level, initially thought to have secondary PHA1 due to the associated UTI and posterior urethral valves. His serum aldosterone remained elevated at 5 months of age, despite resolution of salt wasting symptoms. Chromosomal microarray analysis revealed a deletion of exons 3–5 in NR3C2 in the patient and his asymptomatic mother who also had elevated serum aldosterone level, confirming that he had primary or autosomal dominant PHA1. Our case raises the possibility that some patients with secondary PHA1 attributed to UTI and/or UTM may instead have primary autosomal dominant PHA1, for which genetic testing should be considered to identify the cause, determine future recurrence risk, and possibly prevent the life-threatening salt wasting in a subsequent family member. Future clinical research is needed to investigate the potential overlapping between secondary PHA1 and primary autosomal dominant PHA1.

Biochemical markers of bone turnover in children with clinical bone fragility

Abstract Background: The role of biochemical bone turnover markers (BTMs) in assessing low bone mass and monitoring bisphosphonate treatment in pediatric patients with clinical bone fragility is not well established. The aim of the study was to examine the correlations of BTMs and the bone mineral density (BMD), and evaluate the effects of bisphosphonates therapy on BTMs in children with clinical bone fragility. Methods: Clinical data of 115 patients with clinical bone fragility (mean age 9.7±5.8 years), 102 of whom received bisphosphonates, were studied. Serum alkaline phosphatase (ALP), osteocalcin (OC), urine pyridinoline (PD) and deoxypyridinoline (DPD), BMD at baseline and subsequent years were analyzed. Results: There was a significant negative correlation between urine PD and lumbar BMD (slope=–0.29, p<0.001). There were no correlations between BTMs and lumbar BMD Z-score. There was a significant positive correlation between serum OC and serum ALP, urine PD and DPD (p<0.001). Serum OC, urine PD and DPD index, as expressed as measured value/upper limit of normal value for age, decreased during the first 3 years of bisphosphonate therapy. Conclusions: In children with clinical bone fragility, BTMs correlated with each other, but not with lumbar BMD Z-score. While they were not reliable predictors of degree of low BMD, the bone markers showed suppression during bisphosphonate therapy and may be helpful in monitoring the response to therapy.

Successful Medical Therapy for Hypophosphatemic Rickets due to Mitochondrial Complex I Deficiency Induced de Toni-Debré-Fanconi Syndrome

Primary de Toni-Debré-Fanconi syndrome is a non-FGF23-mediated hypophosphatemic disorder due to a primary defect in renal proximal tubule cell function resulting in hyperphosphaturia, renal tubular acidosis, glycosuria, and generalized aminoaciduria. The orthopaedic sequela and response to treatment of this rare disorder are limited in the literature. Herein we report a long term followup of a 10-year-old female presenting at 1 year of age with rickets initially misdiagnosed as vitamin D deficiency rickets. She was referred to the metabolic bone and genetics clinics at 5 years of age with severe genu valgum deformities of 24 degrees and worsening rickets. She had polyuria, polydipsia, enuresis, and bone pain. Diagnosis of hypophosphatemic rickets due to de Toni-Debré-Fanconi syndrome was subsequently made. Respiratory chain enzyme analysis identified a complex I mitochondrial deficiency as the underlying cause. She was treated with phosphate (50–70 mg/kg/day), calcitriol (30 ng/kg/day), and sodium citrate with resolution of bone pain and normal growth. By 10 years of age, her genu valgus deformities were 4 degrees with healing of rickets. Her excellent orthopaedic outcome despite late proper medical therapy is likely due to the intrinsic renal tubular defect that is more responsive to combined alkali, phosphate, and calcitriol therapy.

Adrenal Function Testing Following Hormone Therapy for Infantile Spasms: Case Series and Review of Literature

Prednisolone and adrenocorticotropic hormone (ACTH) are “hormone” therapies for infantile spasms. There is limited data on the occurrence of decreased adrenal reserve or signs of clinical adrenal insufficiency after hormone therapy. This is a retrospective medical record review of patients referred to our Infantile Spasms Program. Our standardized infantile spasms management guideline began in September 2012 and initially included a post-hormone laboratory assessment of adrenal function. Medical records were assessed for hormone treatments, adrenal function testing, and signs of adrenal insufficiency. Forty-two patients who received one or both hormone therapies met inclusion criteria. A post-hormone laboratory assessment of adrenal function was done in 14 patients. Of these 14 patients, 2 had an abnormal laboratory assessment of adrenal function, both by adrenal stimulation testing – one after ACTH and one after prednisolone. One patient received hydrocortisone replacement and the other received stress dose hydrocortisone as needed; neither patient developed signs of adrenal insufficiency. Another patient treated with both types of hormone therapy in tandem, who did not have a post-hormone laboratory assessment, developed signs of mild adrenal insufficiency and required replacement hydrocortisone. Our study suggests that adrenal suppression can occur after modern hormone therapy regimens. We found two patients with abnormal adrenal function testing after hormone therapy and another patient with signs adrenal insufficiency. Given the seriousness of adrenal crisis, caregiver education on the signs of adrenal insufficiency is critical. Greater vigilance may be indicated in patients receiving both types of hormone therapy in tandem. Although a routine post-hormone laboratory assessment of adrenal function may not be feasible in all patients, replacement or stress dose hydrocortisone is necessary for all patients with suspected adrenal insufficiency.

Cervicofacial subcutaneous emphysema in a 4-year-old boy

A 4-year-old boy presented with left-sided face and neck swelling that started soon after blowing up balloons. He also had symptoms of mild pain on his left cheek. He was afebrile with no difficulty breathing and no periorbital or lip swelling. On examination, crepitus was elicited over the oedematous area on his left-sided cheek and neck, without localised heat, or erythema. Differential diagnoses of facial swelling include allergic or drug reaction, cellulitis or trauma, none of which fit with his presentation. He was diagnosed with cervicofacial …

Zoledronic acid in pediatric metabolic bone disorders

Zoledronic acid (ZA), a highly potent intravenous bisphosphonate (BP), has been increasingly used in children with primary and secondary osteoporosis due to its convenience of shorter infusion time and less frequent dosing compared to pamidronate. Many studies have also demonstrated beneficial effects of ZA in other conditions such as hypercalcemia of malignancy, fibrous dysplasia (FD), chemotherapy-related osteonecrosis (ON) and metastatic bone disease. This review summarizes pharmacologic properties, mechanism of action, dosing regimen, and therapeutic outcomes of ZA in a variety of metabolic bone disorders in children. Several potential novel uses of ZA are also discussed. Safety concerns and adverse effects are also highlighted.

Severe hyponatraemia with absence of hyperkalaemia in rapidly progressive Addison's disease

We present a case of rapidly progressing Addisons disease in adrenal crisis with severe hyponatraemia and absence of hyperkalaemia in a 10-year-old girl. She presented with 2 weeks of vomiting, fatigue and weight loss. Her serum electrolytes obtained 1 week prior to presentation were normal, except for mild hyponatraemia at 131 mmol/L, which dropped to 112 mmol/L on admission. She had normal serum potassium, low-serum osmolality, with elevated urine sodium and osmolality, indistinguishable from syndrome of inappropriate antidiuretic hormone (SIADH). Subsequently, Addisons disease was diagnosed on the basis of gingival hyperpigmentation and undetectable cortisol on adrenocorticotropic hormone stimulation test. She rapidly responded to stress dose hydrocortisone, followed by hydrocortisone and fludrocortisone replacement therapy. The absence of hyperkalaemia in the presence of severe hyponatraemia cannot rule out Addisons disease in children. The mechanism of hypo-osmolar hyponatraemia in primary adrenal insufficiency and clinical clues to differentiate it from SIADH are discussed.