Pseudohypoparathyroidism type 1b (PHP-1b) is usually diagnosed on various symptoms of hypocalcemia. Previous studies reported a few cases of autosomal dominant pattern PHP-1b identified on familial analysis with asymptomatic hypocalcemia. Herein we report the case of a 6-year-old male patient with sporadic PHP-1b incidentally detected on preoperative examination. He had neither characteristic findings of Albright hereditary osteodystrophy nor evidence of tetany. Sporadic PHP-1b was diagnosed on the basis of clinical observation and laboratory examination. In addition, genetic testing using methylation-specific multiplex ligation-dependent probe amplification indicated broad methylation abnormalities and confirmed the sporadic form of PHP-1b. Sporadic PHP-1b might often be overlooked when diagnosis is done simply on definitive clinical features. To avoid this, DNA sequencing and methylation analysis should be performed even in the absence of definitive clinical features.
Keywords: GNAS; asymptomatic hypocalcemia; methylation abnormality; methylation-specific multiplex ligation-dependent probe amplification; pseudohypoparathyroidism.
© 2016 Japan Pediatric Society.