A Case of Psuedohypoparathyroidism Unmasked by COVID-19 and Rhabdomyolysis

Background: Psuedohypoparathyroidism type 1 b (PHP 1b) is a rare condition characterized by hormone resistance with PTH. It is caused by imprinting defect of the GNAS gene and is acquired as autosomal dominant. Compared with Pseudohypoparathyroidism type 1a (PHP1a), PHP1b does not have the characteristic physical features know as Albright hereditary osteodystrophy or AHO. Results: 12-year-old female with unremarkable past medical history presented with seizures. She has been complaining of leg pain for a week but on the day of presentation noted to have stiffening and shortness of breath. There was no history of cough, fever, leg trauma, headache, dysuria, hematuria or dark urine. She had no significant family history. Work up revealed severe hypocalcemia of 4.6 mg/ dL and elevated phosphorus (7.1mg/dl). There was no hypoglycemia and other electrolytes including renal function were normal. Patient also had normal inflammatory markers, normal fibrinogen, and normal ferritin. Urine was positive for trace protein and was positive for myoglobin. Alkaline phosphatase was normal. Urine toxicology screen was negative. Hand X-rays did not showed the shortening of metacarpal bones and kidney ultrasound was normal. After IV calcium bolus, calcium barely increased at 5.0. Interestingly CK was noted to be elevated at 3,794 U/L. Patient physical exam was normal and there was no signs of Albright hereditary osteodystrophy (AHO). Patient was positive for COVID19. Patient required intensive fluid therapy to correct CK which increased up to 11,223 U/L on 3rd day of admission. It eventually came down back to normal on the 6th day. Creatinine levels remained normal. Patient continued to receive high dose calcium and calcitriol supplement and discharged with calcium of 8.5 mg/dL and phosphorus of 7.8 mg/dL. Additional work up showed PTH of 885 pg/mL consistent with pseudohypoparathyroidism. Vitamin D levels and thyroid function were normal. Genetic testing for pseudohypoparathyroidism is awaited. Conclusion: Psuedohypoparathyroidism type 1 b (PHP 1b) is a rare endocrine disorder presenting with hypocalcemia, hyperphosphatemia and increased PTH values due to a variable resistance to target organs. As in our case it was unmasked by COVID 19 infection and rhabdomyolysis. Best of our knowledge there is no such unusual case reported in children. Severe hypocalcemia likely due to combination of factors including tissue calcium deposition, hyperphosphatemia, and skeletal resistance to PTH. As published in some recent reports, this case also illustrates that rhabdomyolysis could be potential complication of SARS- CoV2 infection in early stage with normal renal function, which warrants further research.