Metabolic Bone Disease in Children

Metabolic Bone Diseases and New Drug Developments

Metabolic bone diseases are serious health issues worldwide, since several million individuals over the age of 50 are at risk of bone damage and should be worried about their bone health. One in every two women and one in every four men will break a bone during their lifetime due to a metabolic bone disease. Early detection, raising bone health awareness, and maintaining a balanced healthy diet may reduce the risk of skeletal fractures caused by metabolic bone diseases. This review compiles information on the most common metabolic bone diseases (osteoporosis, primary hyperparathyroidism, osteomalacia, and fluorosis disease) seen in the global population, including their symptoms, mechanisms, and causes, as well as discussing their prevention and the development of new drugs for treatment. A large amount of research literature suggests that balanced nutrition and balanced periodic supplementation of calcium, phosphate, and vitamin D can improve re-absorption and the regrowth of bones, and inhibit the formation of skeletal fractures, except in the case of hereditary bone diseases. Meanwhile, new and improved drug formulations, such as raloxifene, teriparatide, sclerostin, denosumab, and abaloparatide, have been successfully developed and administered as treatments for metabolic bone diseases, while others (romososumab and odanacatib) are in various stages of clinical trials.

Childhood hypophosphatasia: to treat or not to treat

Background

Hypophosphatasia (HPP) is a rare inborn error of metabolism that results from dysfunction of the tissue non-specific alkaline phosphatase enzyme. Its manifestations are extremely variable, ranging from early lethality to disease limited to the dentition. The disease is life-threatening when manifesting within the first six months of life, excepting the extremely rare benign perinatal hypophosphatasia. Childhood hypophosphatasia, defined as onset of symptoms between six months and eighteen years, can manifest as rickets, pain, decreased mobility, deficits of growth, and fractures. Historical treatment has generally involved a combination of dietary and rehabilitative interventions.

Main document

Asfotase alfa (Strensiq™), is a first-in-class bone-targeted recombinant tissue nonspecific alkaline phosphatase which has shown significant improvements in morbidity and mortality in patients with perinatal and infantile hypophosphatasia. Subsequent research has also shown improvements in morbidity for patients with childhood hypophosphatasia as measured by improvement in rickets, growth, strength, mobility, and quality of life. This enzyme replacement therapy has generally been well-tolerated, with most adverse reactions being mild-to-moderate in nature.

The author shares their approach to decisions on commencement of ERT based from experience of managing approximately fifteen patients across the age spectrum. This approach focuses on assessing the severity of five key manifestations of childhood HPP: decreased mobility, pain, rickets, deficits of growth, and fractures.

Imaging Findings of Metabolic Bone Disease

Metabolic bone diseases are a diverse group of diseases that result in abnormalities of (a) bone mass, (b) structure mineral homeostasis, (c) bone turnover, or (d) growth. Osteoporosis, the most common metabolic bone disease, results in generalized loss of bone mass and deterioration in the bone microarchitecture. Impaired chondrocyte development and failure to mineralize growth plate cartilage in rickets lead to widened growth plates and frayed metaphyses at sites of greatest growth. Osteomalacia is the result of impaired mineralization of newly formed osteoid, which leads to characteristic Looser zones. Hypophosphatasia is a congenital condition of impaired bone mineralization with wide phenotypic variability. Findings of hyperparathyroidism are the result of bone resorption, most often manifesting as subperiosteal resorption in the hand. Renal osteodystrophy is the collection of skeletal findings observed in patients with chronic renal failure and associated secondary hyperparathyroidism and can include osteopenia, osteosclerosis, and "rugger jersey spine." Hypoparathyroidism is most commonly due to iatrogenic injury, and radiographic findings of hypoparathyroidism reflect an overall increase in bone mass. Thyroid hormone regulates endochondral bone formation; and congenital hypothyroidism, when untreated, leads to delayed bone age and absent, irregular, or fragmented distal femoral and proximal tibial epiphyses. Soft-tissue proliferation of thyroid acropachy is most often observed in the hands and feet. The findings of acromegaly are due to excess growth hormone secretion and therefore proliferation of the bones and soft tissues. Vitamin C deficiency, or scurvy, impairs posttranslational collagen modification, leading to subperiosteal hemorrhage and fractures. ^©RSNA, 2016.