The major symptoms of OFC are bone pain or tenderness, bone fractures, and skeletal deformities such as bowing of the bones. The underlying hyperparathyroidism may cause kidney stones, nausea, constipation, fatigue and weakness. X-rays may indicate thin bones, fractures, bowing, and cysts. Fractures are most commonly localized in the arms, legs, or spine.

The addition of weight loss, appetite loss, vomiting, polyuria, and polydipsia to the aforementioned symptoms may indicate that OFC is the result of parathyroid carcinoma. Parathyroid carcinoma, an uncommon cancer of the parathyroid glands, is generally indicated by serum calcium levels higher than usual, even in comparison to the high serum calcium levels that OFC generally presents with. Symptoms are also often more severe. Generally, the presence of a palpable neck mass is also indicative of the cancer, occurring in approximately 50% of sufferers, but virtually nonexistent in individuals with OFC with a different origin.

Osteitis fibrosa cystica is defined as the classic skeletal manifestation of advanced hyperparathyroidism. Under the ICD-10 classification system, established by the World Health Organization, OFC is listed under category E21.0, primary hyperparathyroidism.

The signs and symptoms of primary hyperparathyroidism are those of hypercalcemia. They are classically summarized by "stones, bones, abdominal groans, thrones and psychiatric overtones".

- "Stones" refers to kidney stones, nephrocalcinosis, and diabetes insipidus (polyuria and polydipsia). These can ultimately lead to renal failure.

- "Bones" refers to bone-related complications. The classic bone disease in hyperparathyroidism is osteitis fibrosa cystica, which results in pain and sometimes pathological fractures. Other bone diseases associated with hyperparathyroidism are osteoporosis, osteomalacia, and arthritis.

- "Abdominal groans" refers to gastrointestinal symptoms of constipation, indigestion, nausea and vomiting. Hypercalcemia can lead to peptic ulcers and acute pancreatitis. The peptic ulcers can be an effect of increased gastric acid secretion by hypercalcemia.

- "Thrones" refers to polyuria and constipation

- "Psychiatric overtones" refers to effects on the central nervous system. Symptoms include lethargy, fatigue, depression, memory loss, psychosis, ataxia, delirium, and coma.

Left ventricular hypertrophy may also be seen.

Other signs include proximal muscle weakness, itching, and band keratopathy of the eyes.

When subjected to formal research, symptoms of depression, pain, and gastric dysfunction seem to correlate with mild cases of hypercalcemia.

In contrast with primary hyperparathyroidism in adults, primary hyperparathyroidism in pediatric patients is considered a rare endocrinopathy. Pediatric primary hyperparathyroidism can be distinguished by its more severe manifestations, in contrast to the less intense manifestations in adult primary hyperparathyroidism. Multiple endocrine neoplasia is more likely to be associated with childhood and adolescent primary hyperparathyroidism. The fundamental skeletal radiologic manifestation include diffuse osteopenia, pathologic fractures and the coexistence of resorption and sclerosis at numerous sites. Skeletal lesions can be specifically bilateral, symmetric and multifocal, exhibiting different types of bone resorption. Pathologic fractures of the femoral neck and spine can potentially initiate serious complications. Because pediatric primary hyperparathyroidism is frequently associated with pathologic fractures it can be misdiagnosed as osteogenesis imperfecta. Pediatric patients with primary hyperparathyroidism are best remedied by parathyroidectomy. Early diagnosis of pediatric primary hyperparathyroidism is all-important to minimize disease complications and start off timely and relevant treatment.

An endocrine bone disease is a bone disease associated with a disorder of the endocrine system. An example is osteitis fibrosa cystica.

Brown tumours consist of fibrous tissue, woven bone and supporting vasculature, but no matrix. The osteoclasts consume the trabecular bone that osteoblasts lay down and this front of reparative bone deposition followed by additional resorption can expand beyond the usual shape of the bone, involving the periosteum thus causing bone pain. The characteristic brown coloration results from hemosiderin deposition into the osteolytic cysts. Hemosiderin deposition is not a distinctive feature of brown tumors; it may also be seen in giant cell tumors of the bone.

Brown tumors may be rarely associated with ectopic parathyroid adenomas or end stage renal osteodystrophy.

Renal osteodystrophy may exhibit no symptoms; if it does show symptoms, they include:

- Bone pain

- Joint pain

- Bone deformation

- Bone fracture

- The broader concept of chronic kidney disease-mineral and bone disorder (CKD-MBD) is not only associated with fractures but also with cardiovascular calcification, poor quality of life and increased morbidity and mortality in CKD patients (the so-called bone-vascular axis). These clinical consequences are acquiring such an importance that scientific working groups (such as the ERA-EDTA CKD-MBD Working Group) or international initiatives are trying to promote research in the field including basic, translational and clinical research.

The brown tumor is a bone lesion that arises in settings of excess osteoclast activity, such as hyperparathyroidism. It is not a true neoplasm, as the term "tumor" suggests; however, it may mimic a true neoplasm. It most commonly affects the maxilla and mandible, though any bone may be affected. Brown tumours are radiolucent on x-ray.

Bone disease is common among the elderly individual, but adolescents can be diagnosed with this disorder as well. There are many bone disorders such as osteoporosis, Paget's disease, hypothyroidism. Although there are many forms of bone disorders, they all have one thing in common; abnormalities of specific organs involved, deficiency in vitamin D or low Calcium in diet, which results in poor bone mineralization.

To confirm the diagnosis, renal osteodystrophy must be characterized by determining bone turnover, mineralization, and volume (TMV system) (bone biopsy). All forms of renal osteodystrophy should also be distinguished from other bone diseases which may equally result in decreased bone density (related or unrelated to CKD):

- osteoporosis

- osteopenia

- osteomalacia

- brown tumor should be considered as the top-line diagnosis if a mass-forming lesion is present.

Fibrous dysplasia is a mosaic disease that can involve any part or combination of the craniofacial, axillary, and/or appendicular skeleton. The type and severity of the complications therefore depend on the location and extent of the affected skeleton. The clinical spectrum is very broad, ranging from an isolated, asymptomatic monostotic lesion discovered incidentally, to severe disabling disease involving practically the entire skeleton and leading to loss of vision, hearing, and/or mobility.

Individual bone lesions typically manifest during the first few years of life and expand during childhood. The vast majority of clinically significant bone lesions are detectable by age 10 years, with few new and almost no clinically significant bone lesions appearing after age 15 years. Total body scintigraphy is useful to identify and determine the extent of bone lesions, and should be performed in all patients with suspected fibrous dysplasia.

Children with fibrous dysplasia in the appendicular skeleton typically present with limp, pain, and/or pathologic fractures. Frequent fractures and progressive deformity may lead to difficulties with ambulation and impaired mobility. In the craniofacial skeleton, fibrous dysplasia may present as a painless “lump” or facial asymmetry. Expansion of craniofacial lesions may lead to progressive facial deformity. In rare cases patients may develop vision and/or hearing loss due to compromise of the optic nerves and/or auditory canals, which is more common in patients with McCune-Albright syndrome associated growth hormone excess. Fibrous dysplasia commonly involves the spine, and may lead to scoliosis, which in rare instances may be severe. Untreated, progressive scoliosis is one of the few features of fibrous dysplasia that can lead to early fatality.

Bone pain is a common complication of fibrous dysplasia. It may present at any age, but most commonly develops during adolescence and progresses into adulthood.

Bone marrow stromal cells in fibrous dysplasia produce excess amounts of the phosphate-regulating hormone fibroblast growth factor-23 (FGF23), leading to loss of phosphate in the urine. Patients with hypophosphatemia may develop rickets/osteomalacia, increased fractures, and bone pain.

PDP has a number of visible symptoms. Most important clinical features are: pachydermia (thickening and wrinkling of the skin), furrowing of the face and scalp, periostosis (swelling of periarticular tissue and shaggy periosteal new bone formation of long bones) and digital clubbing (enlargement of fingertips). Other features include excessive sweating, arthralgia and gastrointestinal abnormalities. An overview of all symptoms is provided in table 2.

Table 2. Overview of symptoms

Individuals with an enchondroma often have no symptoms at all. The following are the most common symptoms of an enchondroma. However, each individual may experience symptoms differently. Symptoms may include:

- Pain that may occur at the site of the tumor if the tumor is very large, or if the affected bone has weakened causing a fracture of the affected bone

- Enlargement of the affected finger

- Slow bone growth in the affected area

The symptoms of enchondroma may resemble other medical conditions or problems. Always consult your physician for a diagnosis.

Fibrous dysplasia is a disorder where normal bone and marrow is replaced with fibrous tissue, resulting in formation of bone that is weak and prone to expansion. As a result, most complications result from fracture, deformity, functional impairment, and pain. Disease occurs along a broad clinical spectrum ranging from asymptomatic, incidental lesions to severe disabling disease. Disease can affect one bone (monostotic) or multiple (polyostotic), and may occur in isolation or in combination with cafe-au-lait skin macules and hyperfunctioning endocrinopathies, termed McCune-Albright syndrome. More rarely, fibrous dysplasia may be associated with intramuscular myxomas, termed Mazabraud's syndrome. Fibrous dysplasia is very rare, and there is no known cure. Fibrous dysplasia is not a form of cancer.

Chronic kidney disease–mineral and bone disorder (CKD-MBD) is one of the many complications associated with chronic kidney disease. It represents a systemic disorder of mineral and bone metabolism due to CKD manifested by either one or a combination of the following:

- Abnormalities of calcium, phosphorus (phosphate), parathyroid hormone, or vitamin D metabolism

- Abnormalities in bone turnover, mineralization, volume, linear growth, or strength

- Vascular or other soft-tissue calcification

CKD-MBD explains, at least in part, the high morbidity and mortality of CKD patients, linking kidney and bone disease with cardiovascular complications. It is a matter of discussion whether CKD-MBD may be considered a real syndrome or not.

CKD-MBD broadens the "old" concept of "renal osteodystrophy", which now should be restricted to describing the "bone pathology" associated with CKD. Thus, renal osteodystrophy is currently considered "one" measure of the skeletal component of the systemic disorder of CKD–MBD that is quantifiable by histomorphometry of bone biopsy.

Pachydermoperiostosis (PDP) or primary hypertrophic osteoarthropathy (PHO) is a rare genetic disorder that affects both bones and skin. Other names are idiopathic hypertrophic osteoarthropathy or Touraine-Solente-Golé syndrome. It is mainly characterized by pachydermia (thickening of the skin), periostosis (excessive bone formation) and finger clubbing (swelling of tissue with loss of normal angle between nail and nail bed).

This disease affects relatively more men than women. After onset, the disease stabilizes after about 5–20 years. Life of PDP patients can be severely impaired. Currently, symptomatic treatments are NSAIDs and steroids or surgical procedures.

In 1868, PDP was first described by Friedreich as ‘excessive growth of bone of the entire skeleton’. Touraine, Solente and Golé described PDP as the primary form of bone disease hypertrophic osteoarthropathy in 1935 and distinguished its three known forms.

An enchondroma may occur as an individual tumor or several tumors. The conditions that involve multiple lesions include the following:

- Ollier disease (enchondromatosis) - when multiple sites in the body develop the tumors. Ollier disease is very rare.

- Maffucci's syndrome - a combination of multiple tumors and angiomas (benign tumors made up of blood vessels).

Mild or early cases of Pagets are asymptomatic, and so most people are diagnosed with Paget's disease incidentally during medical evaluation for another problem. Approximately 35% of patients with Paget's have symptoms related to the disease when they are first diagnosed. Overall, the most common symptom is bone pain. When symptoms do occur, they may be confused with those of arthritis or other disorders, and so diagnosis may be delayed.

Paget's may first be noticed as an increasing deformity of a person's bones.

Paget's disease affecting the skull may lead to loss of hearing in one or both ears due to compression of the nerves in the inner ear. Rarely, skull involvement may lead to compression of the nerves that supply the eye, leading to vision loss.

The symptoms of Gorham's disease vary depending on the bones involved. It may affect any part of the skeleton, but the most common sites of disease are the shoulder, skull, pelvic girdle, jaw, ribs, and spine.

In some cases there are no symptoms until a fracture occurs either spontaneously or following minor trauma, such as a fall. There may be an acute onset of localized pain and swelling. More commonly there is pain of no apparent cause that increases in frequency and intensity over time and may eventually be accompanied by weakness and noticeable deformity of the area. The rate of progression is unpredictable and the prognosis can be difficult. The disease may stabilize after a number of years, go into spontaneous remission, or, in cases involving the chest and upper spine, prove fatal. Recurrence of the disease following remission can also occur. Involvement of the spine and skull base may cause a poor outcome from neurological complications. In many cases, the end result of Gorham's disease is severe deformity and functional disability.

Symptoms such as difficulty breathing and chest pain may be present if the disease is present in the ribs, scapula, or thoracic vertebrae. These may indicate that the disease has spread from the bone into the chest cavity. The breathing problems may be misdiagnosed as asthma, because the damage done to the lungs can cause the same types of changes to lung function testing that are seen in asthma. Extension of the lesions into the chest may lead to the development of chylous pleural and pericardial effusions. Chyle is rich in protein and white blood cells that are important in fighting infection. The loss of chyle into the chest can have serious consequences, including infection, malnutrition, and respiratory distress and failure. These complications or their symptoms, such as difficulty breathing, chest pain, poor growth or weight loss, and infection have sometimes been the first indications of the condition.

An osteolytic lesion (from the Greek words for "bone" (ὀστέον), and "to unbind" (λύειν)) is a softened section of a patient's bone formed as a symptom of specific diseases, including breast cancer and multiple myeloma. This softened area appears as a hole on X-ray scans due to decreased bone density. Osteolytic lesions can cause pain, increased risk of bone fracture, and spinal chord compression. These lesions can be treated using biophosphonates or radiation, though new solutions are being tested in clinical trials.

Hematologic manifestations related to bone marrow suppression and subsequent pancytopenia are a major source of morbidity and mortality. Additionally extramedullary hematopoiesis can result in liver and spleen dysfunction. Cranial nerve dysfunction and neurologic complications are usually associated with infantile osteopetrosis. Expansion of the skull bone leads to macrocephaly. Additionally, linear growth retardation that is not apparent at birth, delayed motor milestones and poor dentition can occur.

The causes of adult osteomalacia are varied, but ultimately result in a vitamin D deficiency:

Osteomalacia is a generalized bone condition in which there is inadequate mineralization of the bone. Many of the effects of the disease overlap with the more common osteoporosis, but the two diseases are significantly different. There are two main causes of osteomalacia:

1. insufficient calcium absorption from the intestine because of lack of dietary calcium or a deficiency of, or resistance to, the action of vitamin D

2. phosphate deficiency caused by increased renal losses.

Symptoms:

Osteomalacia in adults starts insidiously as aches and pains in the lumbar (lower back) region and thighs before spreading to the arms and ribs. The pain is symmetrical, non-radiating and accompanied by sensitivity in the involved bones. Proximal muscles are weak, and there is difficulty in climbing up stairs and getting up from a squatting position.

As a result of demineralization, the bones become less rigid. Physical signs include deformities like triradiate pelvis and lordosis. The patient has a typical "waddling" gait. However, these physical signs may derive from a previous osteomalacial state, since bones do not regain their original shape after they become deformed.

Pathologic fractures due to weight bearing may develop. Most of the time, the only alleged symptom is chronic fatigue, while bone aches are not spontaneous but only revealed by pressure or shocks.It differs from renal osteodystrophy, where the latter shows hyperphosphatemia.

Osteosclerosis is a disorder that is characterized by abnormal hardening of bone and an elevation in bone density. It may predominantly affect the medullary portion and/or cortex of bone. Plain radiographs are a valuable tool for detecting and classifying osteosclerotic disorders. It can manifest in localized or generalized osteosclerosis. Localized osteosclerosis can be caused by Legg–Calvé–Perthes disease, sickle-cell disease and osteoarthritis among others. Osteosclerosis can be classified in accordance with the causative factor into acquired and hereditary.

In the animal kingdom there also exists a non-pathological form of osteosclerosis, resulting in unusually solid bone structure with little to no marrow. It is often seen in aquatic vertebrates, especially those living in shallow waters, providing ballast as an adaptation for an aquatic lifestyle. It makes bones heavier, but also more fragile. In those animal groups osteosclerosis often occurs together with bone thickening (pachyostosis). This joint occurrence is called pachyosteosclerosis.