Complex mesoectodermal hereditary disorder characterized by focal dermal atrophy, with herniation of fat-producing multiple papillomas, in association with skeletal, dental, ocular, and other anomalies.
Focal Dermal Hypoplasia (FDH).
N.B.: Do not confuse with Goltz-Gorlin Syndrome [inheritable disease characterized by multiple cutaneous nodules with a tendency to become malignant].
Frequency is approximately 2:100,000 newborns.
95% sporadic. X-linked dominant with in utero lethality in males or by a sex-limited gene of variable expressivity. Gene is located on Xp22.31. Only 10% of cases occur in males (possibly the result of half-chromatid mutations).
The underlying molecular defect in FDH is not clear. Based on the common findings of syndactyly, oligodactyly, and polydactyly, the fetal expression of FDH is postulated to occur before week 8 of gestation because the hands and feet have differentiated and developed separate and elongated digits by the eighth week. Because skin and bone lesions generally follow the lines of Blaschko, mosaicism with random X-chromosome inactivation is probable. Clinical abnormalities indicate a profound dysplasia of ectodermal, neuroectodermal, endodermal, and mesodermal elements. Various in vitro observations of fibroblasts from lesional skin reveal abnormal growth kinetics of fibroblasts (increase in the fibroblast doubling time), abnormal glycosaminoglycan metabolism (decreased accumulation of hyaluronic acid), and absence of basement membrane Type IV collagen. A hypothesis that aberrant dermal fibroblast growth and altered collagen fibers may be the basis of the skin defects in FDH has been suggested.
Usually female gender. Characteristic skin findings are present at birth (streaky areas of hyperpigmentation, atrophy, and telangiectasia and groups of soft, yellow-red nodules). Radiologic examination shows longitudinal striation of the long bones with crossing of the epiphyses (osteopathia striata). The combination of split-hand with syndactyly and absence of rays, the so-called lobster-claw hand, is a striking feature of the disorder.
Patients with areas of total absence of skin at birth have been reported. More commonly, skin changes are usually present at birth or develop shortly thereafter from erythematous areas. Papillomas usually develop later, involving the mucous membranes or skin. Lesions of the oropharynx and peritonsillar regions have been described. The presence of laryngeal papillomas most often requires a tracheostomy. Esophageal papillomas associated with strictures have also been described with this condition. In addition, anomalies involving the hands (syndactyly, polydactyly, camptodactyly, missing digits or entire hand), skeleton (hypoplasia or aplasia or the truncal skeleton), mouth (lip papillomas, hypoplastic teeth), and eyes (coloboma of iris and choroid, strabismus, microphthalmia) have been present in some cases. Gastroesophageal reflux, short stature, and mental retardation occur in many patients. The course of the disease and its prognosis depend upon the type and severity of noncutaneous (visceral) involvement. The treatment is symptomatic. One ...