Idiopathic Osteosclerosis

This report describes 6 cases of osteosclerosis which, though resembling a type of hyperphosphatasemia (15, 16), do not have all its characteristics and may represent a variant of one or two types of osteosclerosis previously reported.

Since 1958, the Atomic Bomb Casualty Commission (ABCC) has been clinically examining a defined population biennially in Hiroshima and Nagasaki. This program, sponsored by ABCC and the Japanese National Institute of Health (JNIH), is known as the Adult Health Study, and the details of this program are described elsewhere (6).

The initial 2 cases in this series are of members of the Adult Health Study program. They were detected when an increase in density of the thoracic skeleton was noted on routine chest roentgenography. Survey skeletal roentgenograms verified this initial impression. Additional laboratory data and detailed family histories were obtained. It was then found that the 2 propositi are sisters. Both were exposed to the A-bomb at greater than 5,000 m from the hypocenter. Subsequent evaluation of the other family members has revealed 4 additional cases.

Evaluation of all 6 patients consisted of detailed family histories, physical examinations by one of the authors, radiographic skeletal surveys, and various detailed laboratory studies. For both propositi 24-hour urine values and renal clearances of creatinine, phosphorus, and calcium were also obtained.

Results

Family Description and Medical Evaluation

Twenty living members of the family tree are shown in Figure 1. To date, 13 of these (8 females and 5 males), ranging in age from thirteen to fifty years, have been studied. None experienced exposure to the A-bomb at less than 5,000 m.

In the 13 patients studied, the 6 with osteosclerosis ranged from fifteen to forty-nine years of age. Five were female (Fig. 1). Complete clinical histories and physical examinations failed to reveal any pertinent symptoms or physical findings. Heights and weights were normal for japanese of these ages and sex. The general physical appearance was also unremarkable except for moderate prominence of the chin and broadness of the face (Fig. 2).

Roentgenological Findings

Abnormal roentgenological findings in the 6 positive cases consisted of a diffuse symmetrical increase in bone density involving most of the skeleton. It appeared predominantly in the skull and decreased in degree caudally. This skull change was marked in 5 of the subjects and was minimal in 1, an adolescent. The cortex of all the bones was increased in density, with encroachment of the medullary portions and obliteration of diploe. The thickening of bones in the skull approximated twice the average. There was little if any increase in diameter of the long bones. A striking increase in bone density was seen throughout the skull, especially in the calvaria.