xeroderma pigmentosum

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Epidemiology

rare

autosomal recessive
7 different complementation groups XP-A to XP-G have been identified.
5 of these genes have been cloned XPAC, XPBC, XPCC, XPDC, XPFC & XPGC
a defect in DDB2 is a cause of XP-E
a defect in POLH (XPV) is associated with mild disease
group A patients (defect in XPAC) show the most severe skin symptoms & progressive neurologic disorder

variable, depending upon genetic defect
may be limited to photo-induced deterioration of the skin & eyes with skin neoplasms at a later age (XPV)
may be serious mutilating disorder
skin
- photosensitivity
  - skin lesions are first noted during infancy or early childhood
  - sun exposed areas such as the face, neck, hands & arms are most severely involved, but lesions may occur at other sites including the scalp
  - skin lesions consist of erythema, scaling, bullae, crusting, ephelides, telangiectasia, keratosis,
ocular manifestations
- photophobia, lacrimation, blepharitis, symblepharon, keratitis, corneal opacities, tumors of the lids & possible eventual blindness.
neurologic abnormalities
- mental deterioration & sensorineural deafness may develop in some patients
syndromes
- association of xeroderma pigmentosum with microcephaly, mental retardation, dwarfism & hypogonadism is known as De Santis-Cacchione syndrome
some complementation group XP-B & XP-D patients present with features of Cockayne syndrome
life span is often quite brief

↑ Nelson Textbook of Pediatrics, 14th ed., Behrman et al (eds) WB Saunders, Philadelphia, 1992, pg 1651