Primary Congenital Glaucoma - Glaucoma

Diagnosis

Indications for Testing

• Cornea clouding – in infant or child
• Persistent red eye – test family members of affected child for carrier status
• Carrier screening – for other family members when a causative CYP1B1 mutation is identified
• Prenatal testing – for at-risk pregnancies in families where the causative CYP1B1 mutations are known

Laboratory Testing

• CYP1B1 gene sequencing
  • Gene occurrence in congenital glaucoma
    • Familial – 20-100%
    • Nonfamilial – 10-15%
  • Absence of mutations does not necessarily rule out carrier status or the presence of disease

Differential Diagnosis

• Corneal edema or opacity
  • Ocular
    • Birth trauma
    • Sclerocornea
    • Keratitis
    • Peters anomaly
  • Systemic
    • Mucopolysaccharidoses
    • Cystinosis
    • Niemann-Pick disease
    • Familial dysautonomia
• Corneal enlargement
  • Axial myopia
  • Hereditary megalocornea
  • Keratoglobus
• Epiphora and red eye
  • Conjunctivitis
  • Corneal abrasion
  • Uveitis
  • Keratitis
• Photophobia
  • Ocular
    • Keratitis
    • Aniridia
    • Iritis
    • Cataract
  • Systemic
    • Albinism
    • Meningitis
    • Posterior fossa tumor

Clinical Background

Glaucoma is the second leading cause of blindness in the world and the leading cause of blindness among Africans Americans. Primary congenital glaucoma (PCG) is the most common childhood glaucoma. A notable subtype, newborn PCG, may often have the most severe and clinically challenging expression. Mutations in the CYP1B1 gene are responsible for >50% of cases in some populations.

Epidemiology

• Incidence
  • 1/5,000-20,000 in U.S.
  • 1/2,500 in Middle East
  • 1/1,250 in Slovakian gypsies
• Prevalence – 4% of childhood blindness attributable to PCG
• Age – usually recognized by ≤2 years
• Sex
  • M>F, 3:1 in U.S.
  • M<F, 2:3 in Japan

Inheritance

• Autosomal recessive inheritance of mutations in the CYP1B1 gene
  • Homozygosity – predictive of disease
  • Heterozygosity – carrier status; carriers are unaffected

Pathophysiology

• Abnormality of trabecular meshwork creates an abnormal filtration angle
• Abnormal angle creates resistance to ocular aqueous outflow
  • Results in increased intraocular pressure

Clinical Presentation

• Ocular symptoms vary in severity – bilateral 70% of the time
• Symptoms
  • Photophobia
  • Epiphora
  • Blepharospasm
  • Chronic red or irritated eyes
  • Cloudy/poor vision
• Signs
  • Globe enlargement and edema
  • Iris and pupillary abnormalities
  • Optic nerve cupping
  • Myopia
  • Corneal opacification
  • Elevated intraocular pressure

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory