Phacomatosis pigmentokeratotica Q85.8

Combination of a systematized nevus sebaceus and a systematized nevus spilus. Characteristic associations are:

• hemiatrophy with muscle weakness
• segmental dysesthesia
• segmental hyperhidrosis
• epilepsy and deafness
• Ptosis
• strabismus.

Genetically, this phacomatosis is based on a non-allelic didymosis(twin spots). Postzygotic HRAS mutations are also found in phacomatosis pigmentokeratotica both in the nevus sebaceus and in the melanocytic nevus portion (here in the melanocytes) (Groesser L et al. 2013).

1. Groesser L et al (2013) Phacomatosis pigmentokeratotica is caused by a postzygotic HRAS mutation in
   amultipotent progenitor cell. J Invest Dermatol 133:1998-2003.
2. Happle R (1996) Phacomatosis pigmentokeratotica: A melanocytic-epidermal twin nevus syndrome. Am J Med gene 65: 363-365
3. Saraswat A et al (2003) Phacomatosis pigmentokeratotica associated with hypophosphataemic vitamin D-resistant rickets: improvement in phosphate homeostasis after partial laser ablation. Br J Dermatol 148: 1074-1076