Genetic transmission of tumoral calcinosis: autosomal dominant with variable clinical expressivity.

Tumoral calcinosis is a rare inherited metabolic disorder characterized by hyperphosphatemia, elevated serum 1,25-dihydroxyvitamin D levels and periarticular cystic and solid calcifications. Based on previous investigations, the inheritance of this disorder has been postulated to be autosomal recessive. This interpretation was based on finding clinically affected subjects in only single generations of kindreds. We investigated four generations of an affected kindred and found nine subjects with the disease. A unique dental lesion which is specific for this disorder and serves as a phenotypic marker was identified in two generations of the kindred. In all affected subjects, elevated serum 1,25-dihydroxyvitamin D levels were found, although each member did not have the classical clinical findings of tumoral calcinosis. The possibility that this disorder may be variably expressed and have multiple formes frustes has not been previously considered. Using the unique dental lesion as well as the classical clinical and biochemical abnormalities, we found that in this kindred, tumoral calcinosis is transmitted in an autosomal dominant mode, with variable clinical expressivity.

The concurrence of hypoparathyroidism provides new insights to the pathophysiology of X-linked hypophosphatemic rickets.

Controversy exists over the role that PTH and extracellular fluid calcium concentration may play in modulation of the renal phosphate transport defect in X-linked hypophosphatemic rickets. In previous studies, administration of PTH to affected subjects resulted in an increase or no effect on renal phosphate excretion, while calcium infusion increased renal tubular phosphate transport. In contrast, patients with X-linked hypophosphatemic rickets and hyperparathyroidism have no change in their renal phosphate wasting after parathyroidectomy. However, none of these were permanently hypoparathyroid postoperatively. We describe a patient with idiopathic hypoparathyroidism in whom we proved the coexistence of X-linked hypophosphatemic rickets using family history and dental abnormalities. Initially, the patient had a mean serum calcium level of 5.6 +/- 0.07 (+/- SE) mg/dl and a renal tubular maximum for reabsorption of phosphate per liter glomerular filtrate (TmP/GFR) of 6.5 +/- 0.46 mg/dl. Hypoparathyroidism was confirmed, and therapy with vitamin D (50,000 U/day) and calcium (1,000 mg/day) was begun. On this regimen, serum calcium rose to 8.1 +/- 0.2 mg/dl, and TmP/GFR declined to 2.59 +/- 0.12 mg/dl. Bone biopsy revealed the persistence of osteomalacia. Subsequently, therapy with 1,25-dihydroxyvitamin D3 (1.0 microgram/day) was initiated, and serum calcium rose to 9.6 +/- 0.07 mg/dl, and TmP/GFR declined to 1.79 +/- 0.16 mg/dl. The prevailing serum calcium level correlated inversely with the TmP/GFR (r2 = 0.91; P less than 0.001). These data indicate that calcium and/or PTH are involved in modulation of the renal phosphate transport defect in X-linked hypophosphatemic rickets.

Dental lesions in tumoral calcinosis.

Tumoral calcinosis (TC) is a rare inherited autosomal dominant metabolic disease manifested by elevated serum phosphorus and 1,25 dihydroxyvitamin D levels and periarticular cystic and solid tumorous calcifications. The dental findings in a large family have been critical in determining the genetic transmission of the condition. Radiographically the teeth have short bulbous roots, pulp stones and partial obliteration of the pulp cavity. Histologically, coronal dentin and a variable amount of radicular dentin appears to be deposited regularly. At nonspecific points the developing radicular dentin appears to encounter a mass of calcified material and proceed to grow around it. This mass has a unique histologic pattern with ovoid spaces surrounded by amorphous calcification. At levels of further root development the radicular dentin has an irregular bending tubule arrangement. The dental lesion of TC appears to be different from that of radicular dentin dysplasia in histologic structure and in the method of initiation of the dentin defect. These data suggest that the specific dental lesion is a new phenotypic marker for TC.