Two cases of pseudohypoparathyroidism type ia in duozygotic twins with different phenotypes

Early Diagnosis of Pseudohypoparathyroidism before the Development of Hypocalcemia in a Young Infant

Pseudohypoparathyroidism (PHP) is a rare, heterogeneous disorder characterized by end-organ resistance to parathyroid hormone (PTH). PTH resistance causes elevated PTH levels, hypocalcemia, and hyperphosphatemia. Since hypocalcemia causes life-threatening events, early diagnosis is crucial. However, the diagnosis of PHP is elusive during infancy because PHP is usually diagnosed with hypocalcemia-induced symptoms, which develop later in childhood when calcium requirements increase. A 1-month-old girl was referred to our clinic for elevated thyroid-stimulating hormone (TSH) levels on newborn screening. When measured 1 month after levothyroxine treatment, her TSH level normalized. At 4-months-old, multiple hard nodules were noted on her trunk. A punch skin biopsy revealed osteoma cutis associated with Albright’s hereditary osteodystrophy, a major characteristic of PHP. We performed targeted sanger sequencing of the GNAS gene and detected a heterozygous variant c.150dupA (p.Ser51Ilefs*3) in both the proband and her mother, causing frameshift and premature termination mutations. The patient was diagnosed with PHP Ia when she had normal calcium, phosphorous, and PTH levels. We report the early diagnosis of PHP Ia without hypocalcemia. It emphasizes the importance of meticulous physical examination in patients with congenital hypothyroidism.

Longitudinal growth of the short bones of the hand in a girl with pseudohypoparathyroidism type ia

Brachydactyly is a common feature of pseudohypoparathyroidism (PHP) type Ia. We studied the longitudinal growth of the short bones in the hand of a 15-yr-old girl with PHP type Ia who had been followed for congenital hypothyroidism. Radiographs of the hand of the patient, who had been X-rayed every year since 2 yr of age, were studied. She showed cone-shaped epiphyses of the hand at 2 yr of age before showing brachydactyly. At 4 yr of age, she showed brachydactyly and an advanced bone age, and some short bones were prematurely fused at 6 yr of age. The short bones without cone-shaped epiphyses were also short as a result of a disturbance of the longitudinal bone elongation. In conclusion, the brachydactyly of PHP type Ia is thus considered to be caused by both early epiphyseal fusion with cone-shaped epiphyses and a disturbance of the longitudinal bone elongation.