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Etiology and Pathology

The first two patients were described in 1898 by Giard in France; another followed rapidly, described by Duret in Paris in 1899. It was not until 1934 that the fourth case was recorded, but thereafter the numbers have steadily increased, one series alone adding 56 patients. In a review, Viegas and colleagues reported that there were over 2000 listed cases (1985) and many more have been added since. Many are not reported in the literature.

The majority of patients are melanotic, in either Africa or North America, or Melanesians in PapuaNew Guinea, but numerous reports in the last few years have described tumoral calcinosis in people of all ethnic groups. Patients range in age from 3 months to 70-80 years. The peak incidence is between 10 and 20 years. There is no significant gender preponderance, although there is a considerable variation in the different series. Some have reported an increased incidence in women, others have found the disease to be more common in men.

In some series there is a familial incidence, perhaps in one-third of the patients, and almost always in siblings. A 50% prevalence in affected generations has been suggested, with several members of one generation of one kindred. We have not been able to find any record of more than one generation being affected, even though one theory describes tumoral calcinosis as the result of an inborn error of calcium metabolism. This grouping of a disease in male or female members of a sibship suggests an autosomal dominant pattern of inheritance, with variable clinical expressivity. It can equally suggest some other common factor of nutrition, infection, or life-style. In a few instances, tumoral calcinosis has been associated with other genetic abnormalities, including pseudoxanthoma elasticum, Down's syndrome, and Engelmann's disease. Most large series do not show a predominance of patients with a familial relationship, but it is difficult to be sure of paternity in some societies and "my brother" or "my sister" may not indicate shared genes. Because of its relatively high frequency in Africa, tumoral calcinosis has been linked to an "African gene", but this cannot be confirmed in the literature. There are too many recorded cases in other groups to make this possibility convincing.

The etiology remains controversial. There are almost as many theories as there are papers on the subject, and such proliferation of ideas usually indicates that the correct answer is still unknown. Because it is common in developing countries, it has been linked to sleeping on the ground, hard floors, or hard beds. These are unlikely causes because many patients with tumoral calcinosis have slept in soft beds all their lives and, even in developing countries, the tumors appear in anatomical sites where chronic trauma is minimal. Some tumoral calcinosis has been linked to direct trauma, such as a blow a few weeks or months previously: however, many of the tumors occur without any history of trauma and in parts of the body which suggest that chronic trauma is as unlikely as acute trauma, and would not be overlooked had it consistently occurred. There are histological and clinical differences between tumoral calcinosis and soft tissue calcification of known traumatic origin, such as myositis ossificans. It has been suggested that parasites may be causal, but no parasitic remains have ever been identified in the tumors, and the disease is known in countries where parasites would be an unlikely cause. A combination of trauma and genetics has been postulated: this explanation does not appear any more satisfactory than the others. It has all been neatly summarized by the statement that "understanding is incomplete:" As so often happens, these theoretical discussions do not alter the fact that clinically it is almost always easy to make the correct diagnosis after seeing the radiographs.

In the search for the cause, extensive metabolic and other laboratory studies have been undertaken, but the results have proved inconsistent. In the majority of patients, almost all serological and biochemical tests are normal and no dietary link has been established. Sophisticated laboratory investigations (see below) provide evidence in some patients of an error in calcium and phosphate metabolism. Vitamin D has been implicated but a high intake of any vitamin has been excluded in the vast majority of recorded cases. Necrosis does not play any part in the etiology. There have been some very lengthy and careful investigations of the tumors and the patients, but the riddle has yet to be solved to everyone's satisfaction.

The first two patients were described in 1898 by Giard in France; another followed rapidly, described by Duret in Paris in 1899. It was not until 1934 that the fourth case was recorded, but thereafter the numbers have steadily increased, one series alone adding 56 patients. In a review, Viegas and colleagues reported that there were over 2000 listed cases (1985) and many more have been added since. Many are not reported in the literature.

The majority of patients are melanotic, in either Africa or North America, or Melanesians in PapuaNew Guinea, but numerous reports in the last few years have described tumoral calcinosis in people of all ethnic groups. Patients range in age from 3 months to 70-80 years. The peak incidence is between 10 and 20 years. There is no significant gender preponderance, although there is a considerable variation in the different series. Some have reported an increased incidence in women, others have found the disease to be more common in men.

In some series there is a familial incidence, perhaps in one-third of the patients, and almost always in siblings. A 50% prevalence in affected generations has been suggested, with several members of one generation of one kindred. We have not been able to find any record of more than one generation being affected, even though one theory describes tumoral calcinosis as the result of an inborn error of calcium metabolism. This grouping of a disease in male or female members of a sibship suggests an autosomal dominant pattern of inheritance, with variable clinical expressivity. It can equally suggest some other common factor of nutrition, infection, or life-style. In a few instances, tumoral calcinosis has been associated with other genetic abnormalities, including pseudoxanthoma elasticum, Down's syndrome, and Engelmann's disease. Most large series do not show a predominance of patients with a familial relationship, but it is difficult to be sure of paternity in some societies and "my brother" or "my sister" may not indicate shared genes. Because of its relatively high frequency in Africa, tumoral calcinosis has been linked to an "African gene", but this cannot be confirmed in the literature. There are too many recorded cases in other groups to make this possibility convincing.

The etiology remains controversial. There are almost as many theories as there are papers on the subject, and such proliferation of ideas usually indicates that the correct answer is still unknown. Because it is common in developing countries, it has been linked to sleeping on the ground, hard floors, or hard beds. These are unlikely causes because many patients with tumoral calcinosis have slept in soft beds all their lives and, even in developing countries, the tumors appear in anatomical sites where chronic trauma is minimal. Some tumoral calcinosis has been linked to direct trauma, such as a blow a few weeks or months previously: however, many of the tumors occur without any history of trauma and in parts of the body which suggest that chronic trauma is as unlikely as acute trauma, and would not be overlooked had it consistently occurred. There are histological and clinical differences between tumoral calcinosis and soft tissue calcification of known traumatic origin, such as myositis ossificans. It has been suggested that parasites may be causal, but no parasitic remains have ever been identified in the tumors, and the disease is known in countries where parasites would be an unlikely cause. A combination of trauma and genetics has been postulated: this explanation does not appear any more satisfactory than the others. It has all been neatly summarized by the statement that "understanding is incomplete:" As so often happens, these theoretical discussions do not alter the fact that clinically it is almost always easy to make the correct diagnosis after seeing the radiographs.

In the search for the cause, extensive metabolic and other laboratory studies have been undertaken, but the results have proved inconsistent. In the majority of patients, almost all serological and biochemical tests are normal and no dietary link has been established. Sophisticated laboratory investigations (see below) provide evidence in some patients of an error in calcium and phosphate metabolism. Vitamin D has been implicated but a high intake of any vitamin has been excluded in the vast majority of recorded cases. Necrosis does not play any part in the etiology. There have been some very lengthy and careful investigations of the tumors and the patients, but the riddle has yet to be solved to everyone's satisfaction.

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Copyright: Palmer and Reeder