Pseudopseudohypoparathyroidism

GS undefined

Pseudopseudohypoparathyroidism (30 letters) (pseudoPHP) is an inherited disorder that closely simulates the symptoms, but not the consequences of pseudohypoparathyroidism, thus it has mild or no manifestations of hypoparathyroidism or tetanic convulsions. The term pseudopseudohypoparathyroidism is used to describe a condition where the individual has the phenotypic appearance of pseudohypoparathyroidism type 1a, but is biochemically normal.

As such, a haploinsufficiency results similar to pseudohypoparathyroidism 1A, which is caused by a similar defect on the corresponding maternal chromosome. However, unlike pseudohypoparathyroidism 1A, which presents with all the symptoms of hypoparathyroidism except the low parathyroid hormone levels, pseudopseudohypoparathyroidism presents only with the skeletal defects and none of the defects in calcium and phosphate homeostasis. Patients generally have normal calcium and phosphate levels and normal parathyroid hormone levels. As such, it is sometimes considered a variant of Albright hereditary osteodystrophy.

Presentation
Short stature may be present.

Hormone resistance is not present.

Obesity is less common in pseudopseudohypoparathyroidism than in pseudohypoparathyroidism.

A mother who has inherited pseudopseudohypoparathyroidism from her father may in turn pass along pseudohypoparathyroidism 1A to her children as the imprinting pattern on the inherited paternal chomosome will be changed to the maternal pattern in the mother's ovum during meiosis.