Pseudohypoparathyroidism

Pseudohypoparathyroidism (PHP) is a condition where 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 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

• parathyroid hormone level: high
• serum phosphate level: high
• serum calcium level: low  

Radiographic features

Musculoskeletal manifestations

• short stature and 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 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