Focal dermal hypoplasia (FDH – also known as Goltz syndrome) is a rare multisystemic genetic disorder. It is particularly known to affect the skin, skeleton, eyes and dentition, but can also affect other systems such as the gastroenterological system, heart and neurological system.
FDH can be inherited in an X-linked dominant pattern, or may arise from novel mutations in the developing embryo. It is due to a faulty ‘PORCN’ gene on the X chromosome, hence females (XX) with one affected chromosome develop the disease; most male (XY) embryos with an affected X chromosome do not survive to birth. As a result, the majority of people with FDH are female.
Signs and symptoms
The signs of FDH can usually be seen from birth, they can be divided as follows according to the body system they affect:
- Linear bands of thinned (hypoplastic skin) which follow Blaschko’s lines. These may also be hypo- or hyperpigmented.
- Localised absent skin layers (aplasia cutis congenita)
- Subcutaneous fat herniation
- Osteopathia striata (striated bones on x-ray)
- Abnormalities of hands and feet (syndactyly, brachydactyly, ectrodactyly)
- Cleft lip/palate
- Dental abnormalities: enamel hypoplasia, microdontia, irregular spacing, malocclusion
- Micropthalmia or anopthalmia (small or absent eyes)
- Colboma (a defect in a structure of the eye – e.g. iris. Can affect multiple structures)
- Abnormal lacrimal duct
FDH can also affect other organs such as the kidneys, GI tract, heart and nervous system.
A diagnosis of FDH is made based on clinical features, the patient can then undergo genetic testing to look for the affected PORCN gene. To diagnose FDH, a patient would usually have to exhibit multiple key skin findings (as listed above) or a key limb finding in addition to a skin finding.
Differentials for FDH include other rare genetic disorders, such as:
- Micropthalmia with linear skin defects
- Incontinentia pigmenti
- Rothmund-Thomson syndrome
FDH is a genetic disease for which there is no cure, however treatment can be directed at symptom management to improve quality of life for patients and prevent complications. This requires a multi-disciplinary approach, with the involvement of specialties such as dermatology, ophthalmology, orthopaedics and dentists.