OCCIPITAL HORN SYNDROME
 
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OCCIPITAL HORN SYNDROME

 

DEFINITION:

A disorder of copper metabolism characterized by congenital cutis laxa, hyperextensible and hypermobile digits, and bony protuberances of the occiput.

EPIDEMIOLOGY:

  • incidence: rare (about 100 cases reported)
  • age of onset:
    • first decade of life
  • risk factors:
    • familial - X-linked recessive
      • chrom.#: X
      • gene: ? lysyl oxidase
    • Males only

PATHOGENESIS:

1. Background

  • there are 3 inherited disorders known to be caused by genetic defects in copper metabolism:
    • Wilson Disease
    • Menkes Disease
    • Occipital Horn Syndrome (OHS)
  • OHS is considered to be a less severe allelic form of Menkes Disease (Chelly and Monaco, Nature Genetics 5:317-318, 1993) and in older liturature used to be called Ehlers-Danlos Syndrome IX and X-linked Cutis Laxa
  • the function of various cuproenzymes is dependent on copper:

1. Oxidases

  • ascorbate oxidase, cytochrome c oxidase, lysyl oxidase, monamide oxidase

2. Others

  • dopamine-beta-hydroxylase, superoxide dismutase, tyrosinase

2. Genetic Defect

  • genetic defect -> defect in copper metabolism (perhaps copper transport) -> decreased lysyl oxidase activity -> disruption of collagen and elastin crosslinking -> connective tissue manifestations/dysmorphisms

CLINICAL FEATURES:

1. Connective Tissue Dysmorphisms

1. Cutaneous

1. Cutis Laxa

  • lax, soft, loose, wrinkled, hyperextensible skin especially on the face giving the patient an 'aged appearance'

2. Skeletal

1. Major

  • occipital horns (bony protuberance of the occiput)
  • hyperextensible and hypermobile digits
  • limited extension of the elbows and knees

2. Others

  • carpal bone coalescences
  • delayed fontanelle closure
  • luxatio coxarum
  • osteomalacia
  • short clavicles
  • short stature

3. Systemic

1. Respiratory

  • emphysema
  • laxity of vocal cords

2. Cardiovascular

  • postural hypotension
  • vascular wall aneurysms and vascular stenoses

3. Gastrointestinal

  • chronic diarrhea
  • inguinal hernias
  • multiple GI diverticula, hernias, and prolapses

4. Genitourinary

  • bladder or ureteric diverticulae +/- spontaneous rupture

2. Others

  • muscular weakness
  • low normal intelligence to mild mental retardation

INVESTIGATIONS

1. Diagnosis

  • increased serum copper and ceruloplasmin
  • decreased lysyl oxidase activity in cultured cells and samples of skin
  • excess copper and increased copper accumulation in cultured fibroblasts

2. Imaging Studies

1. Skeletal X-Rays

  • occipital exostoses
  • shortened clavicles with thickened "hammerlike" distal ends

2. Voiding Cystouretrogram

  • bladder or ureteric diverticulae

3. Angiograms

  • arterial tortuosity, elongation, and stenosis

MANAGEMENT:

1. Supportive

  • no treatment for underlying disorder
  • multidisciplinary approach
    • Paediatrics, Orthopedics
    • genetic counselling
    • moniter for complications, i.e., diverticulae, aneurysms, chronic diarrhea, inguinal hernias
    • parenteral copper administration does not correct the low lysyl oxidase activity

 

 

 

 

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