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Abstract: FR-PO624

A Rare Case of Pseudohypoparathyroidism Type 1B Diagnosed by Methylation-Specific Multiplex Ligation-Dependent Probe Amplification (MS-MLPA)

Session Information

Category: Genetic Diseases of the Kidneys

  • 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Choi, Hong Sang, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
  • Kim, Minah, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeollanam-do, Korea (the Republic of)
  • Oh, Tae ryom, Chonnam National University Hospital, Gwangju, Korea (the Republic of)
  • Suh, Sang Heon, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
  • Kim, Chang Seong, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
  • Ma, Seong Kwon, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
  • Kim, Soo Wan, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
  • Bae, Eun Hui, Chonnam National University Medical School, Gwangju, Korea (the Republic of)
Introduction

Pseudohypoparathyroidism (PHP) is a rare disorder characterized by hypocalcemia, hyperphosphatemia, and increased serum parathyroid hormone (PTH). Pseudohypoparathyroidism type 1B (PHP1B) is a subtype of PHP characterized by isolated renal PTH resistance, usually without physical abnormalities such as Albright hereditary osteodystrophy or other endocrine abnormalities. We present a rare case of PHP1B presented as hypocalcemia with elevated PTH.

Case Description

A 33-year-old man visited the nephrology department outpatient clinic with abnormal laboratory finding. His serum calcium level was 5.9 mg/dL in recent health exam. He had a history of dyslipidemia without any medication. He complained of tingling sensation in hands and eyelid twitching. On physical examination, he showed Chvostek’s sign. His laboratory findings included a serum calcium level of 7.7 mg/dL, a serum ionized calcium level of 1.74 mEq/L, a serum phosphorus level of 4.7 mg/dL, a serum creatinine level of 0.9 mg/dL and a serum PTH level of 284.2 pg/mL. A serum 25-hydroxyvitamin D level of 27.5 ng/mL and a serum 1,25-dihydroxyvitamin D level of 28.2 pg/mL. Under strong suspicion of PHP, DNA sequence analysis and methylation specific multiplex ligation-dependent probe amplification (MS-MLPA) of the GNAS and STX16 genes was performed. MLPA analysis of GNAS gene revealed methylation abnormality in multiple differentially methylated region (DMR). Finally, he diagnosed as PHP1B. He is on outpatient follow-up with adequate calcium replacement and no specific symptoms.

Discussion

The exact prevalence of PHP is not yet known. PHP1B can be sporadic or familial. The genetic characteristics of most sporadic PHP1B is still not well-known but GNAS imprinting abnormalities, hypomethylation at A/B DMR has been reported. Symptoms of PHP1B usually begin in childhood due to low calcium levels and may include numbness, seizures, tetany, cataracts, and dental problems. However, as in our case, specific symptoms may not occur until adulthood. Therefore, when evaluating the cause of hypocalcemia, it is necessary to differentiate PHP1B even in adults, especially in cases with hyperphosphatemia and high PTH levels.