What Is Osteitis Fibrosa Cystica?
Osteitis fibrosa cystica (OFC) is a disorder and a severe medical complication that involves the bone resulting from excessive parathyroid hormone (PTH) production due to hyperactivity of the parathyroid gland. The changes in the bone are a late presentation of hyperparathyroidism. Hyperparathyroidism means either one or both of the parathyroid glands produce too much parathyroid hormone (PTH). The PTH hormone is essential for the health of the bones, but excess of this hormone can weaken the bones abnormally and lead to deformity. PTH induces the activity of osteoclasts (bone cells that break down bone tissues), resulting in bone breakdown. It is a rare complication that affects less than 5 percent of people with hyperparathyroidism.
What Causes Osteitis Fibrosa Cystica?
Osteitis fibrosa cystica (OFC) results from the overproduction of parathyroid hormone (PTH). PTH elevates blood calcium levels through the release of calcium from the bones and the reabsorption of calcium in the kidney. OFC is caused by increased production of PTH that can be the result of any of the following mechanisms:
Parathyroid Adenoma
These are noncancerous (benign) parathyroid gland tumors. Although benign, they are active metabolically. They result in almost 85 percent of hyperparathyroidism cases.
Hereditary Factors
About 5 to 10 percent of cases of hyperparathyroidism result from hereditary factors such as-
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Multiple endocrine neoplasias (MEN) type 1 and 2A- Group of genetic disorders affecting the hormone-producing endocrine glands.
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Hyperparathyroidism-jaw tumor syndrome- An inherited disorder causing overactivity and tumors of parathyroid hormones and multiple tumors in the jaws.
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Familial isolated hyperparathyroidism- A rare inherited condition causing one or more tumors to form in the parathyroid glands, which can result in OFC if left undiagnosed.
The most common cause of hereditary hyperparathyroidism is MEN type 1 and accounts for up to 95 percent of congenital cases of OFC.
Parathyroid Carcinoma
Parathyroid carcinoma is an extremely rare but malignant (cancerous) condition affecting the parathyroid glands and accounts for less than one percent of hyperparathyroidism cases. The diagnosis of OFC due to parathyroid carcinoma is challenging.
Renal Complications
Renal osteodystrophy is a disorder of the bones that results from end-stage renal disease (ESRD), which can commonly cause OFC (up to 50 percent). During ESRD, kidneys cannot make calcitriol, which promotes the delivery of calcium to the bones. In calcitriol deficiency, PTH levels increase and encourage the removal of calcium from the bones.
Osteitis fibrosa cystica is currently very rare in people with hyperparathyroidism who have good accessibility to medical care. It is found to be more common in people who develop hyperparathyroidism early on in their life or who have hyperparathyroidism left untreated for a long time.
What Are the Symptoms of OFC?
The symptoms of OFC are due to the softening of the bones and hypercalcemia (high calcium levels) and include-
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Bone pain and tenderness.
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Bone fractures.
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Kidney stones.
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Peptic ulcer.
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Weight loss.
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Nausea and vomiting.
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Loss of appetite.
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Fatigue and weakness.
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Frequent urination.
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Depression.
How Is OFC Diagnosed?
Blood tests help with the laboratory findings, which include-
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Increased PTH levels in the blood.
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Increased calcium levels in the blood.
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Decreased phosphate levels in the blood.
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Normal or elevated alkaline phosphatase.
An X-ray may reveal areas of bone thinning, fractures, and if there is any bowing or deformity in the bones. People with hyperparathyroidism are predisposed to osteopenia (thin bones) and osteoporosis, making the bone brittle and more susceptible to fractures. Teeth X-ray may also show abnormalities.
A CT (computed tomography) scan and ultrasound may also be used to diagnose parathyroid gland disorders.
OFC usually occurs in the 40s and 50s and most commonly affects females. If it occurs at a younger age, it may mean that a hereditary condition would be causing it.
How Is OFC Treated?
If the osteitis fibrosa cystica is caused by an abnormal parathyroid gland, the best treatment option for the individual may be to have it removed surgically (parathyroidectomy). The treatment of osteitis fibrosa cystica begins with the management of hyperparathyroidism, which is usually the surgical removal of the gland, which is called parathyroidectomy, and should take place after fixing the underlying metabolic issues. The surgery can be performed safely and effectively. The other remaining parathyroid glands may be able to make sufficient levels of PTH as compensation for the loss of one gland. Following parathyroidectomy, the majority of the associated bone problems resolve and can be reversed.
Suppose surgery is not the treatment option, or some people may choose not to have the gland removed. In that case, medications may be an option to treat and manage the associated hypercalcemia (elevated calcium levels), deficiency of vitamin D, and other symptoms. This is determined by the levels of calcium, PTH, phosphate, and vitamin D in the blood.
Calcimimetics are a group of drugs that mimic calcium in the blood. They work by “tricking” the parathyroid gland into producing less PTH. Bisphosphonates are also prescribed for bone mass loss, but they are supposed to be used for the short term. Women going through or have recently gone through menopause are usually susceptible to osteoporosis, and therefore hormone replacement therapy may help retain more calcium.
What Are the Possible Complications of OFC?
The possible complications of OFC may include the following-
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Pain in the bones.
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Fractures of the bones.
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Deformity in the bones.
Complications due to hyperparathyroidism may include kidney stones and kidney failure.
Conclusion:
Osteitis fibrosa or osteitis fibrosa cystica (OFC) is a rare but severe bone disorder that results in complications of an abnormality of parathyroid glands or hyperparathyroidism, which causes the release of excess parathyroid hormone. The severity of the OFC may be prevented if hyperparathyroidism is detected and diagnosed early and treated accordingly. If the treatment is delayed or left untreated, it may lead to serious complications. A few earlier steps, such as maintaining bone health and managing calcium levels by regular blood tests, may be preventative and improve the outcome. Talk to the healthcare provider about the symptoms they may experience and start the treatment as early as possible. The last treatment option is surgery or parathyroidectomy, which involves removing either one or all the parathyroid glands.
