Pseudohypoparathyroidism

Pseudohypoparathyroidism occurs when there is end-organ resistance to parathyroid hormone (PTH).

Epidemiology

Pseudohypoparathyroidism has an estimated prevalence of 1.1 per 100,000 people ⁶.

Clinical Presentation

• hypocalcemia and tetany

• short stature

• developmental delay

Pathology

Subtypes

There are several recognized subtypes which include:

• type I: abnormal cyclic adenosine monophosphate (cAMP) response to PTH stimulation

  • type Ia (Albright hereditary osteodystrophy (AHO)): has characteristic phenotypical features

  • type Ib: lacks phenotypical features

• type II: normal cAMP response to PTH stimulation

Markers

• PTH level: high

• serum phosphate level: high

• serum calcium level: low  

Radiographic features

Musculoskeletal manifestations

• short stature

• obesity

• brachydactyly

  • short metacarpals (inclusive of short 4^th/5^th metacarpals)

  • short metatarsals

• soft tissue calcification

• exostoses: short metaphyseal or more central and perpendicular to the long axis of a bone

• broad bones with coned epiphyses

CNS & head and neck manifestations

• basal ganglia calcification

• sclerochoroidal calcification ⁴

• deep white matter calcification