= focal dermal hypoplasia

= X-linked dominant connective tissue genodermatosis

Genetics: defect in PORCN gene encoding a key protein involved in developmental Wnt signaling pathway

• soft red-yellow nodules in linear arrangement = fat herniating through hypoplastic dermis; short stature
  Location: antecubital + popliteal fossa
• characteristic asymmetric erythematous / hyperpigmented / hypopigmented atrophic linear streaks:
• ± telangiectasia (often) ± superficially erosions + ulcers

Age: present at birth

• scoliosis
• generalized osteopenia
• osteopathia striata = bilateral symmetric vertical metaphyseal striations of long bones with sparing of vertebrae and ilia
• skeletal defects:
  Location: hand, foot (60%)
  • “lobster claw” deformity = split hands and feet
  • clinodactyly, oligodactyly, polydactyly, syndactyly
• regional asymmetric underdevelopment
• spina bifida
• rib and clavicular abnormalities