Abstract 48: Calcinosis cutis with hyperphosphatemia; A red herring or an etiology?

Introduction: Calcinosis cutis is an uncommon diseasethat results inprogressive deposition ofinsoluble calcium salts (crystals of calcium phosphate, hydroxyapatite) in the skin which can be intracutaneous, subcutaneous, intramuscular or intravisceral. Here we have described a very interesting case of idiopathic calcinosis cutis with mild hyperphosphatemia which didn't respond to phosphate-lowering therapy. Case description: A 12-year-old female presented with multiple cutaneous papules with chalky white discharge over both hands, left knee and both feet for last 2 years. The lesions got ulcerated and healed by hyperpigmentation. Initial metabolic workup revealed hyperphosphatemia and normocalcemia but her lesions remain unchanged after 6 months of phosphate-lowering therapy. On examination we foundmultipleerythematous firm nodule and plaqueover right 5th finger, left thumband right great toe along with multiple discharging sinuseswith bony swelling in left knee joint. There was no skin tightening or oral opening narrowing. There was no history of recurrent renal calculi, bony deformity or recurrent fragility fractures. Our biochemical evaluation revealed mild hyperphosphatemia (6.64 mg/dl with age-specific upper limit of 5.9); Ca-9.85 mg/dl, 25 (OH) D- 14.60 ng/ml, iPTH- 92.2 pg/ml. Rest all metabolic parameters including renal functions were normal. 24 hours urinary phosphorus excretion and TmP/GFR didn't reveal any abnormality along with normal FGF-23 (59.73 pg/ml). Markers for autoimmune diseases were non-reactive. The lesion biopsyruled out dermatomyositis. The patient was started on sodium metabisulphite along with diltiazem60 mg/day. The patient has improved significantly after 3 months of therapy. Discussion: Dystrophic calcification is the commonest form which is characterized by calcification occurring in the dead or damaged tissue. Metastatic calcification occurs in calcium phosphorus combined products of more than 70. Inadvertent intake of calcium or phosphorus can lead to iatrogenic calcification. Initial mild hyperphosphatemia prompted a diagnosis of metastatic calcification in this case and the patient was put on sevelamer without any use. Mild hyperphosphatemia can be found in idiopathic calcinosis where no phosphate binder is warranted. In our case, a diligent and judicious biochemical workup ruled out hyperphosphatemic tumoral calcinosis and other causes of dystrophic calcifications. Conclusion: The presence of mild hyperphosphatemia is red herring in our case. A judiciousapproach is prudent in any case of calcinosis to avoid over-treatment.