Blomstrand chondrodysplasia

Template:Blomstrand chondrodysplasia Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]

Overview

Blomstrand chondrodysplasia is a fatal skeletal dysplasia presenting with generalised bone sclerosis and advanced skeletal maturation. Autosomal recessive inheritance has been proposed for this disease and consanguinity increases the chances of Blomstrand chondrodysplasia in offsprings.

Differentiating Blomstrand chondrodysplasia From Other Diseases

Blonstrand chondrodysplasia should be differentiated from other causes of abnormal parathyroid hormone( PTH) and parathyroid hormone resistance such as pseudohypoparathyroidism, acrodysostosis, hypomagnesemia, hypoparathyroidism and hyperparathyroidism.

Differential diagnosis of Pseudohypoparathyroidism
Disorders		Mechanism	Laboratory findings
			Serum PTH	Serum Calcium	Serum Phosphate	Other findings
Pseudohypoparathyroidism	Type 1a	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH) Heterozygous GNAS inactivating mutations that reduce expression or function of Gαs Genetic mutation disrupts both receptor-mediated activation of adenylyl cyclase and receptor-independent activation of the enzyme.	↑	↓	↑	↓ 1,25 Dihydroxy vitamin D ↓ Urinary cAMP ↓ Urinary phosphate
	Type 1b	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH). Familial- heterozygous deletions in STX16, NESP55, and/or AS exons or loss of methylation at GNAS	↑	↓	↑	↓ 1,25 Dihydroxy vitamin D ↓ Urinary cAMP ↓ Urinary phosphate
	Type 1c	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH). Heterozygous GNAS inactivating mutations that reduce expression or function of Gαs Genetic mutation disrupts receptor-mediated activation of adenylyl cyclase but does not affect receptor-independent activation of the enzyme.	↑	↓	↑	↓ 1,25 Dihydroxy vitamin D ↓ Urinary cAMP ↓ Urinary phosphate
	Type 2	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH).	↑	↓	↑	↓ 1,25 Dihydroxy vitamin D Normal urinary cAMP ↓ Urinary phosphate
	Pseudopseudohypoparathyroidism	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH). Combination of inactivating mutations of GNAS1 and Albright's osteodystrophy	Normal	Normal	Normal	--
Hypoparathyroidism		There is deficiency of parathyroid hormone in hypoparathyroidism. Deficiency of parathyroid hormone causes body to decrease: Reabsorption of calcium from bone. Excretion of phosphate. Reabsorbtion of calcium from distal tubules. Vitamin D mediated absorption of calcium from intestine.	↓	↓	↑	↓ 1,25 Dihydroxy vitamin D Normal urinary cAMP Normal urinary phosphate
Hypomagnesemia		Decreased parathyroid hormone (PTH) secretion Skeletal resistance to parathyroid hormone (PTH)	Inappropriately ↓	Normal/↓	--	↓ serum magnesium ↓/Normal serum potassium
Acrodysostosis	Acrodysostosis type 1	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH) PRKAR1A germ-line mutation in the encoding gene resulting in parathyroid resistance	↑	↓	↑	Multiple hormone resistance
	Acrodysostosis type 2	Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH) Phosphodiesterase 4D (PDE4D) gene mutation resulting in parathyroid resistance	↑	↓	↑	Multiple hormone resistance
Blomstrand chondrodysplasia		Genetic defectcausing end organ resistance to the action of parathyroid hormone (PTH) Homozygous or heterozygous mutations in both alleles encoding the type 1 parathyroid hormone receptor resulting in parathyroid resistance	↑	↓	↑	↓ Urinary Phosphate, ↑ Urinary cAMP
Hyperparathyroidism	Primary hyperparathyroidism	Increase in secretion of parathyroid hormone (PTH) from a primary process in parathyroid gland. Parathyroid hormone causes increase in serum calcium.	↑	↑	↓/Normal	Normal/↑ calcitriol
	Secondary hyperparathyroidism	Increase in secretion of parathyroid hormone (PTH) from a secondary process. Parathyroid hormone causes increase in serum calcium after long periods.	↑	↓/Normal	↑	--
	Tertiary hyperparathyroidism	Continuous elevation of parathyroid hormone(PTH) even after successful treatment of the secondary cause of elevated parathyroid hormone. Parathyroid hormone causes increase in serum calcium.	↑	↑	↑	--