MON-LB63 Hypocalcemia-A Clue to Digeorge Syndrome; A Very Rare Case Diagnosed in a 41 Year Male

41-year-old male with history of anxiety, bipolar disorder, depression, cognitive developmental delay, Idiopathic Thrombocytopenic Purpura (ITP), Vit D deficiency, tinnitus, suicidal attempt, auditory hallucination, borderline intellectual functioning comes to the PCP’s office for regular follow-up. The PCP has noted that the patient was hypocalcemic on multiple visits. On exam, vitals were in normal range, height 5 feet 2 inches, BMI 31 kg/m(2).Despite the patient being on calcium and Vit D2 pills for a couple of months, his Calcium level were low ranging from 5.8–7.8mg/dl (normal 8.5-10.1) with normal albumin; ionized calcium was low 0.9-0.97mmol/l (normal 1.12-1.23); Magnesium was normal 2mEq/L (normal 1.5-2.5), phosphorus slightly high 5 mg/dL (normal 2.5-4.9), PTH (ParaThyroid Hormone level) was low-normal 18.8pg/ml (normal 11.1-79.5), vitamin D 25 OH low 16ng/ml (normal 30-100); 1,25 di OH vitamin D low 8ng/ml (normal25-40).Thyroid ultrasound showed 2 benign nodules, no further work-up done. TSH and free T4 were normal. FISH (Fluorescence In Situ Hybridization) came positive for DiGeorge syndrome (deletion at 22q11.2). He was treated with calcium 600 mg 4 pills daily, calcitriol 0.25 mcg two pills daily, Vit D2 50000 IU weekly and thiazide diuretic. His labs improved. DISCUSSIONHypocalcemia can be due to low magnesium level, drugs or associated with high or low PTH. The patient had normal magnesium and he was not on any medication that causes hypocalcemia. This rules out first two casues. Hypocalcemia with high PTH (pseudohypoparathyroidism or low vit D levels) doesn’t fall in our differential because our patient had low PTH. For hypocalcemia with low PTH, differentials include post-surgical condition (no surgical history), autoimmune (history and labs not suggestive of), infiltrative diseases (eg hemochromatosis- he had normal iron study, Wilson disease- normal copper level, granulomas- contrary he had low 1,25 Di OH vit D). Hypocalcemia secondary to genetic parthyroid gland anomaly was thought to be most likely in our patient. So FISH was pursued. Conclusion: For patients with cognitive issues, persistence of chronic hypocalcemia (with low PTH) despite treatment should prompt for genetic disorders like DiGeorge. DiGeorge is usually the diagnosis of children. Perhaps this is the first case of DiGeorge diagnosed so late at age of 41.