Hypercalcemia is a serious condition, which may threaten life. Familial benign hypocalciuric hypercalcemia (FBHH) is a benign situation which develops due to inactivating mutation of calcium sensing receptor (CaSR). Differential diagnosis of FBHH is important in order to prevent unnecessary laboratory tests and treatments.
A three-month-old infant, who was born 2950 g on 38th gestational week to healthy unrelated parents, was admitted to pediatric endocrinology department due to high TSH levels. Her anthropometric evaluation was appropriate for her age and she did not have any dysmorphic stigmata. She was diagnosed with hypothyroidism and put on LT4 treatment. When she was 5 months old, her serum calcium was 11.34 mg/dL (8.8-10.6).
The patient did not have any clinical symptoms of hypercalcemia. Serum phosphorus, parathormone, vitamin levels, urine calcium/creatinine, urine analysis, and renal ultrasonography were normal. Oral hydration was started and her calcium level decreased to 10.8 mg/dL on follow-up. Biochemical and hormonal parameters of father and mother of the patient were evaluated to determine the etiology of hypercalcemia. Whole exome sequencing was performed to the patient and homozygote mutation on exon 7 (p.Glu1011Gln/c.3031G>C) was detected. In order to determine if the parents of the patient had heterozygote mutation or if this is a de novo mutation, genetic analysis was also performed to the parents.
To the best of our knowledge, the mutation found in our patient was not mentioned in the literature before. We think that this mutation may cause FBHH in our case. Functional evaluation should be performed for definitive diagnosis.