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.

Zygomatic salivary gland mucocele in a ferret.

A zygomatic salivary gland mucocele was diagnosed in a 1-year-old female domestic ferret with exophthalmos. A T-shaped incision from near the lateral canthus to the base of the ear and continuing ventrally to the level of the commissure of the mouth was made to expose the mucocele. Surgical removal was complicated by the large open orbit of the ferret, adjacent cellulitis, extension ventromedial to the globe, and difficulty in identifying important motor nerves. Vision was maintained, but slight postoperative enophthalmos and mild upper eyelid paresis developed.