Pseudohypoparathyroidism

Pseudohypoparathyroidism is characterized by elevated plasma levels of PTH and symptoms consistent with reduced PTH levels - hence a resistance of peripheral organs to PTH.

Classification

Type 1 is further branched into types 1a, 1b, 1c. Type 1a is equivalent to Albright hereditary osteodystrophy, type 1b has not skeletal abnormalities, and in type 1c the protein shows normal activity in erythrocytes.

Differentials

Type 1 is cause by mutation or impaired imprinting of GNAS1 gene. In contrast to type 2 the renal cAMP excretion in response to PTH administration is blunted. Type 2 is not yet characterized genetically.

The genetic background of type 2 pseudohypoparathyroidism is not yet characterized. Moreover, severe vitamin D deficiency resembles pseudohypoparathyroidism with normal renal cAMP response to PTH, so an acquired disease or a hereditary disease in vitamin D metabolism have to be ruled out prior to searching a gene responsible for pseudohypoparathyroidism type 2.[Error: Macro 'ref' doesn't exist]

Systematic

Metabolic bone disease
	Hereditary Rickets
	Inherited human diseases of heterotopic bone formation
	Osteopetrosis
	Osteoporosis/renal Osteodystrophy
	Pseudohypoparathyroidism
		Albright hereditary osteodystrophy
			GNAS
		Pseudohypoparathyroidism type IB
			GNAS
			GNAS-AS1
			STX16

References:

1.	Linglart A et al. (2002) GNAS1 lesions in pseudohypoparathyroidism Ia and Ic: genotype phenotype relationship and evidence of the maternal transmission of the hormonal resistance.

2.	Rao DS et al. (1985) Dissociation between the effects of endogenous parathyroid hormone on adenosine 3',5'-monophosphate generation and phosphate reabsorption in hypocalcemia due to vitamin D depletion: an acquired disorder resembling pseudohypoparathyroidism type II.

3.	Drezner M et al. (1973) Pseudohypoparathyroidism type II: a possible defect in the reception of the cyclic AMP signal.

4.	OMIM.ORG article Omim 203330

5.	Orphanet article Orphanet ID 97593

6.	Wikipedia article Wikipedia EN (Pseudohypoparathyroidism)