Metabolic Bone Disease

Metabolic bone disease is a catch-all name for a variety of clinically distinct disorders that share the common feature of an abnormal bone chemical microenvironment, which leads to a deficient skeleton and bone deformities. Metabolic bone diseases frequently have a significant clinical picture and manifestation that is reversible in nature once the underlying problem is addressed. Mineral abnormalities such as calcium, phosphorus, magnesium, or vitamin D might arise as a result of malfunctions in the numerous components that regulate mineral homeostasis. Rickets develops at the epiphyseal growth plates, and osteomalacia develops on the endocortical and cancellous bone surfaces as a result of improper mineralization. Furthermore, the pathophysiology of osteogenesis imperfecta has been broadened from a basic collagen deficiency to include anomalies in bone cell metabolism and development, as well as primary abnormalities in osteoblast differentiation.

Skeletal dysplasias, a wider set of hereditary bone abnormalities that overlaps with metabolic bone disease, must be distinguished from metabolic bone disease. Skeletal dysplasias, as opposed to metabolic bone diseases, are hereditary disorders characterized by extensive cartilage and bone defects. The bone condition is caused by primary abnormalities in various signal pathways or cell types that regulate skeleton formation processes. When dealing with newborns who have several unexplained fractures, forensics experts face a difficult diagnostic issue in distinguishing between child abuse and metabolic bone disease.

Osteoporosis, rickets, osteomalacia, osteogenesis imperfecta, osteopetrosis, Paget disease of bone, and fibrous dysplasia are examples of metabolic bone disorders.

 

What are Metabolic Bone Diseases?

Metabolic bone disease encompasses a wide range of bone problems caused by mineral imbalances such as calcium, phosphorus, magnesium, or vitamin D. Osteoporosis, osteomalacia, rickets, renal osteodystrophy, and Paget's disease of bone are the most frequent metabolic bone disorders. Vitamin D deficiency, familial hypophosphatemia, and hyperparathyroidism are all potential causes of metabolic bone disease.

 

Osteoporosis

Is the most frequent metabolic bone condition. Osteoporosis is a bone disease that causes fragile, weak bones that are more prone to fractures due to a loss in bone mass and strength. Women in their eighties and nineties are the most typically affected. Fractures caused by osteoporosis are more frequent in the hips, wrists, and vertebral segments of the spine. Osteoporosis is referred to as a silent disease since most patients are ignorant of their disease till a bone fracture occurs.

Linear growth retardation, bone abnormalities, non-traumatic fractures, and impairment of motor development and function are all possible outcomes of metabolic bone disease in children.

 

What is an Osteoporosis?

Osteoporosis is a disease that causes the bones in the hip, backbone, and wrist to become fragile to the point of breaking easily. Because you may not notice any changes till a bone break, osteoporosis is known as a silent illness.  The bones, on the other hand, have been deteriorating for years. An elderly woman engages in resistance training.

Bone is a type of living tissue. The body digests old bone tissue and substitutes it with fresh bone tissue to maintain the bones strong. Bone mass stops growing at the age of 30, and the purpose of bone health is to preserve as much bone as possible for as long as feasible. More bone is broken down than is rebuilt when adults hit their 40s and 50s.

A careful examination of the inside of a bone reveals something resembling a honeycomb. When you have osteoporosis, the holes in this honeycomb expand, and the bone that makes up the honeycomb shrinks. The bones' outer layer thins out as well. The bones become weaker as a result of all of this.

 

Osteoporosis Risk Factors

Although osteoporosis can affect anyone at any age, it is more prevalent among the elderly, particularly women. This is a disease that affects both males and females. Osteoporosis is most frequent in white and Asian women. Other women who are at high risk include:

  • Have a family history of fractured bones or osteoporosis 
  • Have fractured bone after the age of 55
  • Had surgery to remove the ovaries before their cycles terminated
  • Had early menopause
  • Have not consumed enough calcium and/or vitamin D during their lifetimes
  • Smoker or second-hand smoker
  • Take certain treatments, such as arthritis and asthma medications, as well as some cancer therapies
  • Have been taking some medications for a long time.
  • Have a petite build

As you get older, your chances of developing osteoporosis increase. For several years after menopause, women may experience rapid bone loss. Following then, the loss slows but persists. Men lose bone mass at a slower rate than women. Men and women, however, lose bone at the same rate at the age of 60 or 70.

 

Osteoporosis Diagnosis

The doctor will likely recommend a bone density scan to confirm osteoporosis, estimate the risk of fracture, and determine whether you require treatment.

This test is performed to determine the density of the bones. Dual-energy x-ray absorptiometry (DEXA) or bone densitometry is the most prevalent method. The DEXA equipment measures the amount of x-rays received by tissues and bone and compares it with bone mineral density.

The DEXA equipment calculates the T and Z scores based on bone density. The T score is used to predict the risk of fracture and the necessity for medication therapy by comparing your bone density to that of a normal population of younger people. The Z score indicates how much bone you have in relation to others your age. This score can assist determine whether more medical tests are required.

The following procedures can be used to determine whether or not a person has osteoporosis-related bone fractures:

  • Bone x-rays produce an image of bones throughout the body, such as the hand, wrist, arm, elbow, shoulder, foot, ankle, thigh, hip, pelvis, and others. It helps to diagnose fractured bones, which can happen as a consequence of osteoporosis.
  • CT scan of the spine is used to check for fractures and alignment. It can be used to assess bone density and predict the likelihood of fragility fractures.
  • Magnetic resonance imaging (MRI) of the spine is used to analyze vertebral fractures for signs of underlying diseases, such as malignancy, as well as to determine whether the fracture is old or fresh. New fractures usually respond better to vertebroplasty and kyphoplasty than older fractures.

 

Osteoporosis Treatment

For the treatment of osteoporosis, there are various FDA-approved drugs to select from, including:

  • Bisphosphonates
  • Calcitonin
  • Hormone therapy
  • RANK ligand inhibitor
  • Selective estrogen receptor modulators
  • Parathyroid hormone analog

These drugs require a prescription and a medical examination prior to treatment.

Osteoporosis can result in compression and fragility fractures in the vertebra. In certain circumstances, radiologist-assisted vertebroplasty and kyphoplasty may be an alternative for treating symptomatic vertebral fractures. With vertebroplasty, a hollow needle is utilized to inject a particular cement mixture into the broken bone using image guidance. A balloon is injected through a needle into the broken bone to form a cavity in kyphoplasty. Following the removal of the balloon, a glue mixture is administered into the cavity. Surgical therapy may be indicated in some cases of compression fracture, especially if the spinal canal is severely narrowed.

 

Rickets and Osteomalacia

Rickets is a condition that impairs the development of the growth plates of bones in children. Rickets can induce leg bending and soreness in the bones. It can also put a child at risk for fractures.

Osteomalacia is a condition that affects both children and adults and is caused by a lack of bone minerals (mostly calcium and phosphate). Osteomalacia, like rickets, can cause bone discomfort and raise the risk of fracture.

Both of these diseases are tightly connected; typically, a child with rickets also has osteomalacia.

 

Rickets and Osteomalacia Causes

Vitamin D insufficiency is the most frequent cause of rickets and osteomalacia (not enough vitamin D). This is usually related to:

  • A diet deficient in vitamin D.
  • Vitamin D synthesis in the skin is inadequate (from having dark-colored skin or keeping skin covered without adequate sun exposure, or living in northern regions of the country). This is particularly problematic during the cold weather.
  • Some medical problems, such as celiac disease, might influence how vitamin D is absorbed from food by a child's intestines.
  • Rare genetic disorders that impact how the body processes vitamin D or phosphate can cause rickets in some people.

 

Rickets and Osteomalacia Symptoms

The patients are usually asymptomatic in the initial stages. Osteomalacia, on the other hand, can lead to the following symptoms as the illness worsens:

  • Muscular pain and weakness, especially after exercise 
  • Bones that fracture more easily, especially those in the hips, back, and feet 
  • Trouble walking and a change in how you walk - maybe with a waddle muscle cramps 
  • Numbness and tingling in the hands and feet due to low serum calcium
  • The legs, groin, thighs, and knees are the most common sites for bone discomfort. When you stand, walk, or run, it can be experienced in the feet.

 

Rickets and Osteomalacia Treatment

The goal of rickets treatment is to replace the vitamin or mineral that has been lost in the body. This will take care of most of the rickets symptoms. If the kid has a vitamin D insufficiency, the doctor would most likely ask them to get as much sun as possible. They will also advise kids to take vitamin D-rich foods like fish, eggs, liver, and milk.

Rickets can also be treated with calcium and vitamin D supplementation. Inquire with the doctor about the proper dosage, as it may differ depending on the patient's size. Too much calcium or vitamin D might be harmful.

If your child has skeletal malformations, braces may be required to keep their bones in the proper place as they grow. If the child's condition is serious, he or she may require corrective surgery. Treatment for genetic rickets requires a mix of phosphate supplementation and elevated amounts of a specific kind of vitamin D.

The treatment for osteomalacia is determined by the underlying cause. Supplements of 800 to 4,000 units per day are used to treat osteomalacia caused by vitamin D insufficiency; alternatively, 50,000 units per week for 8 weeks may be needed.  High-dose treatment of 50,000 to 100,000 units a day or intramuscular doses of 10,000 units a day may be needed to address intestinal malabsorption at first; for sprue, a gluten-free diet is essential.  Vitamin D supplementation of 4,000 units a day, in conjunction with sunlight exposure, may be beneficial in patients with aberrant vitamin D metabolism (e.g., anticonvulsant-induced osteomalacia).  Blood calcium and 25(OH) vitamin D levels must be monitored during high-dose vitamin D treatment.

If serum calcium and creatinine are regularly monitored, calcitriol may be necessary for individuals with renal impairment and insufficient 1,25(OH) vitamin D production. Reference has vitamin D dosing guidelines for patients with stage 3 and 4 chronic kidney disease and patients on dialysis with stage 5 CKD. Oral bicarbonate will treat acidosis in patients with osteomalacia who have renal tubular acidosis. In addition to treatment for the underlying condition, phosphate supplementation and vitamin D mimics are frequently used to treat osteomalacia caused by Fanconi syndrome.

According to a previous study, vitamin D3 is a better option than vitamin D2. The latest evidence has shown that supplementing with animal-sourced vitamin D3 (cholecalciferol) and plant-sourced vitamin D2 (ergocalciferol) at oral doses is equally potent and helpful for bone health.

 

Paget Disease of the Bone

Paget's disease of bone is a skeleton condition that lasts for years. Remodeling is a process that removes aged bone and substitutes it with newer, fresh, and healthy bone. This mechanism becomes out of balance in Paget's disease, leading to irregularly formed, fragile, and brittle new bone. Paget's disease is most common among the elderly, affecting about 2 percent of persons over the age of 55.

Many people with Paget's disease have no symptoms and aren't conscious they have it until they have x-rays for another cause. When bone pain and other symptoms appear, they may be due to the disease itself or its consequences such as arthritis, bone deformities, and fractures.

Treatment for Paget's disease usually includes taking drugs to assist slow or halt the illness' progression. If a patient develops problems, surgery may be required to correct misshapen bones or aid in the healing of fractures.

 

Paget Disease Causes

Paget's disease has yet to be identified. The disorder's etiology, according to experts, could be multifactorial. Paget's disease has no known cause in the majority of cases.

According to studies, Paget's disease may be linked to a slow viral infection of the bone, which can be persistent for years until symptoms manifest.

There is a family history of the illness in roughly 10-30% of cases. Researchers have revealed a number of genes that may predispose people to Paget's disease. The sequestosome 1 gene, the TNFRSF1A gene that codes for the RANK protein, and the VCP gene are all linked to this disorder. The specific role of these genes in the disease's development is uncertain. Family members' susceptibility to the presumed virus could be due to this inherited trait.

 

Paget Disease Symptoms

Bone discomfort, joint pain (particularly in the back, hip, and knee), and headache are early indications of Paget's disease. Expansion and bowing of the thighs and lower legs, as well as expansion of the skull in the region of the forehead, are physical indications. The majority of people with Paget's disease are asymptomatic (have no symptoms) or have relatively moderate symptoms.

Other indications and symptoms often arise as the condition advances. Further bowing of the affected limbs, a waddling gait, joint discomfort and arthritis, fractures of damaged bones, and muscular and sensory abnormalities are also possible.

Hearing loss can occur in up to 45% of those with skull involvement. Loss of eyesight and hydrocephalus, a complication in which an excess of cerebrospinal fluid in the skull creates pressure on the brain's structures, are other symptoms that might develop.

In some circumstances, spinal stenosis develops, which is marked by abnormal narrowing of the openings within the spinal canal, spinal nerve root canals, or the bones of the spinal column. Congestive heart failure is another possibility. Sarcomas (bone tumors) are a rare, but serious, complication.

 

Paget Disease Treatment

The most commonly prescribed therapy for Paget's disease of the bones is bisphosphonates. Bisphosphonates are usually administered through venous injection; however, they can also be taken orally. Bisphosphonates are usually well-tolerated when given orally, however, they can irritate the gastrointestinal tract.

The following are examples of bisphosphonates:

  • Zoledronic acid
  • Pamidronate
  • Ibandronate
  • Alendronate
  • Risedronate

Bisphosphonate treatment has been related to rare cases of severe muscular, joint, or bone pain that does not go away after the medicine is stopped. Bisphosphonates can also raise the risk of a rare disease in which a part of the jawbone dissolves and degrades, which is frequently linked to active dental problems or dental surgery.

If you're allergic to bisphosphonates, the doctor may recommend calcitonin, a naturally occurring hormone that regulates calcium and bone turnover. Calcitonin is a medicine that you can use to treat yourself. It comes in the form of an injection or a nasal spray. Nausea, skin flushes, and injection site soreness are all possible adverse effects.

Surgery may be required in the following rare circumstances:

  • Assist in the healing of fractures
  • Joints that have been destroyed by severe arthritis should be replaced.
  • Re-align misaligned bones
  • Nerve pressure should be reduced.

 

Osteogenesis Imperfecta

Osteogenesis imperfecta is caused by a mutation in the gene that produces the collagen protein. Collagen is a crucial component of bone structure.

Osteogenesis imperfecta is a condition that is passed down from generation to generation. They either have insufficient collagen in their bones or collagen that isn't working properly. Their bones become weaker and more fragile as a result of this. It can also cause abnormalities in the bones.

The gene deficiency can be passed down from one parent to the other.  Children with osteogenesis imperfecta frequently have a parent who suffers from the disease. Occasionally, a gene deficiency occurs spontaneously at the point of conception.

 

Osteogenesis Imperfecta Causes

Osteogenesis imperfecta is inherited from one's parents. The various types are transmitted down in various ways. The gene can be passed down from either one or both parents. A gene can also be handed down by an unexplained alteration in a gene.

The majority of newborns with osteogenesis imperfecta have a genetic abnormality in one of two genes. These genes aid in the formation of collagen. Collagen is a key component of connective tissue, which binds and maintains the whole body, including the bones. Collagen is in short supply due to the defect. Alternatively, the collagen may be aberrant.

 

Osteogenesis Imperfecta Symptoms

Osteogenesis imperfecta symptoms differ widely between and among kinds. Among the signs and symptoms of osteogenesis imperfecta are:

  • Easily fractured bones
  • Bone abnormalities, including legs bowing
  • Discoloration of the sclera (the white of the eye)
  • A barrel-shaped chest
  • A curved spine
  • A triangle-shaped face

 

Osteogenesis Imperfecta Diagnosis

The baby's doctor may recommend you to a consultant who is familiar with identifying and treating osteogenesis imperfecta. For example, the infant could be referred to a genetic specialist or an orthopedist.

The following diagnostic tests may be recommended by the baby's healthcare professional or consultants:

  • X-rays. It is used to evaluate the bone for any fracture.
  • Lab tests. Blood and skin may be examined. The tests may include genetic testing.
  • Dual Energy X-ray Absorptiometry scan (DEXA scan). A scan to check for bone softening.
  • Bone biopsy. A sample of the bone is evaluated.

 

Osteogenesis Imperfecta Treatment

Till now, there is no therapy, medication, or surgery available to cure osteogenesis imperfecta. The goal of treatment is to assist persons with osteogenesis imperfecta to live more independently by increasing bone strength. Treatment options for osteogenesis imperfecta include:

  • Occupational therapy: It is a type of therapy that focuses on fine motor control like buttoning a shirt or tying the boots.
  • Physical therapy: Physical therapists suggest exercises to help people improve their strength, mobility, and range of motion. Assistive devices, such as walkers, canes, and crutches, can help people move about more easily.
  • Dental and oral hygiene: Osteogenesis imperfecta can cause tooth cracking, color alterations, and degeneration. The disorder necessitates routine dental examinations for those who suffer from it.
  • Medications: The clinician may recommend medications to halt bone loss or manage pain, depending on your symptoms.

An orthopedic specialist can treat the kid if they break a bone. The following treatments may be used:

  • Protective devices such as braces, splints, and casts may be used by an orthopedic professional to immobilize broken bones during recovery or following surgery.
  • The doctor may recommend surgery to fix bent or deformed bones. For children with osteogenesis imperfecta, rodding operation is a popular therapy option. A rod is used to keep the bones from fracturing. Bones are also supported by the rods. Some of the types can be changed as the child gets older.

 

Conclusion

Physicians can employ a better understanding of the pathophysiology of bone growth and the clinical, radiological, and histologic characteristics of metabolic bone disease to diagnose and differentiate metabolic bone disease from childhood physical abuse. In cases of healed juvenile rickets or osteogenesis imperfecta, this distinction might be especially difficult. When appropriate, a pathologist with knowledge in infantile rickets can examine bone slices or biopsies to assist identify or rule out the histologic characteristics of certain metabolic bone diseases and distinguish metabolic bone disease patients from child abuse cases.