What is focal dermal hypoplasia?

Focal Dermal Hypoplasia (FDH) is part of a group of diseases called ectodermal dysplasias; they cause hair, teeth, skeleton, nails and glands to form and function abnormally, and they are also inherited. It may also be known as Goltz syndrome.

FDH primarily affects females, with roughly 90% of cases being females; there have been approximately 200 to 300 reported cases worldwide.

This number may be low due to underdiagnosis or misdiagnosis.

FHD is caused by a mutation in the PORCN gene, this is a mistake in the gene that would normally contain instructions for proteins involved in structure. The mutation causes the proteins made to be abnormal or completely absent, causing the symptoms of FHD.¹ 

Symptoms of focal dermal hypoplasia

There is a wide range of potential symptoms that affect the skin, hair, nails and eyes of an affected person.

Skin:

• Congenital patchy skin aplasia (patches of underdeveloped skin or lack of skin)
• Congenital hyper- or hypopigmentation (discoloured skin or no colour)
• Visible veins under skin (face, torso and extremities)
• Congenital nodular fat herniation (nodules that protrude and cause pain)
• Papillomas (wart-like growths)

Nails:

• Ridged nails
• Dysplastic or hypoplastic nails (poor growth, flaking or completely missing nails)

Hair:

• Patchy Alopecia
• Wiry hair

Eyes:

• Iris columbus (a cleft in the iris)
• Small or missing eye (Microphthalmia)
• Crossed eyes.
• Nystagmus (constant, repetitive movement of the eyes)

All these symptoms are possible for a person with Focal Dermal Hypoplasia. Some are present from birth (congenital) or develop later, not every symptom will be suffered, but several will be by a person who has FDH² 

Teeth:

There are specific dental symptoms that are common among those with FDH, these are:

• Grooves down the teeth, to the root.
• Hypodontia - Some teeth are missing.
• Enamel issues.

Skeletal anomalies

With those that have FDH, there is several symptoms that involve the skeletal structure and growth, these are:

• Ectrodactyly (split hand/foot)- missing fingers or toes with syndactyly of the remaining fingers or toes
• Syndactyly- Joined fingers or toes
• Fewer fingers or toes on each hand/foot
• Extra fingers or toes (polydactyly)
• Short stature- caused by long bones being stunted
• Scoliosis (curvature of the spine)
• Fused or underdeveloped vertebrae

These are the most common skeletal symptoms of FDH; they are generally present at birth, but others, such as scoliosis, appear in childhood. They generally affect size and function, though they do not change over time.³ 

There may also be some characteristic features of the face/head that can be present for those with FHD, such as a small head, pointed chin, abnormal external ear, or cleft lip/palate are possible.

These are less common but still possible and may pose issues with development.

Diagnosis

Diagnosis is dependent upon the presence of several symptoms that are characteristic of FDH; these can be identified at birth, with a diagnosis being confirmed with genetic testing for a mutation in the PORCN gene.

Treatment

Focal dermal hypoplasia is incurable, as with all inherited, genetic conditions. Treatment is focused on the symptoms that may arise. Ointments and protective dressings may be useful to protect skin from infection and reduce pain.

There is the possibility of dentures and hearing aids to help with any dental or auditory issues that may arise from FDH.

Occupational therapy is an option for those with some forms of limb deformities, devices to assist in everyday life, may also be of great help and for those who are suitable and require it, surgery can be done.¹ 

The life span of those with FDH may be no different from those without. This is dependent upon the quality of care given.⁴

Summary

Focal Dermal Hypoplasia (FDH), also known as Goltz syndrome, is a rare inherited disorder caused by a mutation in the PORCN gene. This mutation causes abnormal growth of skin, teeth, hair, eyes and bones. Females are the most affected group, with 90% of affected being female, though there are only 200 to 300 reported cases worldwide.

Symptoms can affect many different parts of the body, most notably the skin, eyes, hair, nails and teeth. The most common symptoms in affected people are:

• Patches of underdeveloped or missing skin.
• Papillomas.
• Discoloured or non-pigmented skin.
• Patchy Alopecia.
• Ridged or missing nails.
• Cleft in the iris.
• Missing teeth.
• Enamel issues.

A number of the symptoms together would give a great indication of FDH in a baby.

There are a number of symptoms of FDH that affect the skeleton; in particular, the extremities, the most common and noticeable are:

• Ectrodactyly (split foot/hand)- missing central digits, with the remaining digits joined together
• Syndactyly- fingers or toes join together
• Fewer or extra fingers or toes
• Short stature - caused by shorter long bones in the legs and arms

These are the most common symptoms that are visible at birth and would likely signal FDH. A few years into childhood, someone with FDH may also develop scoliosis.

Treatment of FDH focuses on ensuring a comfortable functioning life and easing any discomfort caused by symptoms. Some surgical intervention may be possible in regards to limb malformation. A person with FDH can have a normal length of life, dependent upon the quality of care.