Pseudohypoparathyroidism Type 1b with Digital Clubbing

Area of Science:

• Endocrinology
• Genetics
• Rare Diseases

Background:

• Pseudohypoparathyroidism (PHP) is characterized by parathyroid hormone (PTH) resistance.
• Albright's hereditary osteodystrophy (AHO) is a common physical manifestation of PHP.
• PHP type 1b involves specific genetic alterations affecting PTH signaling.

Purpose of the Study:

• To report a case of Pseudohypoparathyroidism (PHP) type 1b in a 33-year-old Japanese man.
• To investigate the genetic and clinical features of this PHP patient.
• To explore the potential association between digital clubbing and PHP.

Main Methods:

• Clinical diagnosis of PHP type 1b.
• Biochemical tests including assessment of hypocalcemia, PTH levels, and Ellsworth-Howard test.
• Genetic analysis identifying STX16 exon deletion and imprinting defects (A/B-DMR, AS1-DMR).

Main Results:

• The patient presented with hypocalcemia and preserved PTH secretion.
• The Ellsworth-Howard test indicated decreased urinary cAMP and phosphate excretion.
• Genetic findings included STX16 exon 5-7 deletion and hypomethylation of A/B-DMR and AS1-DMR.
• The patient lacked typical AHO features but had a history of childhood digital clubbing.

Conclusions:

• This case represents Pseudohypoparathyroidism (PHP) type 1b with a distinct genetic profile.
• Digital clubbing, though rare, may be a previously unrecognized phenotype of PHP.
• Further research is needed to understand the full spectrum of PHP manifestations.