What is ichthyosis prematurity syndrome?
Ichthyosis prematurity syndrome is a rare autosomal recessive genetic skin disorder in which affected infants are born prematurely with abnormal skin covered in a thick clay-like vernix.
Their mothers usually develop polyhydramnios, which can precipitate premature labour, and after birth, the affected infant often develops severe, temporary respiratory failure. If the infant survives, the skin may remain red and slightly scaly for the rest of its life.
Ichthyosis prematurity syndrome
Who gets ichthyosis prematurity syndrome?
Ichthyosis prematurity syndrome is a rare condition with less than 100 affected individuals reported worldwide.
Being recessively inherited, both parents must carry a copy of the defective gene in order for this recessive disorder to manifest. Clusters of cases have been reported from Ireland and Scandinavia.
What causes ichthyosis prematurity syndrome?
Ichthyosis prematurity syndrome is caused by mutations of the SLC27A4 gene that codes for the fatty acid transport protein 4 (FATP4), which is responsible for skin barrier function during the embryonic and neonatal period.
This mutation results in abnormal desquamation of keratinocytes into the amniotic fluid, causing polyhydramnios. Aspiration of the excessive amniotic keratinocyte debris into the lungs results in temporary respiratory failure in the days after delivery.
What are the clinical features of ichthyosis prematurity syndrome?
- Premature birth
- Thick and abnormal clay-like vernix coating. If removed by gentle rubbing, the underlying skin is pink and hyperkeratotic
- Early neonatal respiratory failure is usual
- Neonatal asphyxia
- Peripheral blood eosinophilia is usual
Skin changes lessen rapidly, and during later childhood and adulthood, there may be mild ichthyosis and follicular hyperkeratosis.
What are the complications of ichthyosis prematurity syndrome?
- Respiratory distress in the immediate postpartum period.
- Fluid loss from the skin during the neonatal period.
How is ichthyosis prematurity syndrome diagnosed?
The clinical appearance at birth is characteristic even though it is rare. Specific diagnostic tests include:
- Genetic testing: SLC27A4 gene mutation confirms the diagnosis, replacing the need for neonatal skin biopsy (showing hyperkeratosis and follicular plugging).
- Transmission electron microscopy: presence of perinuclear swelling of keratinocytes and trilamellar lamellae in the horny layer.
- Maternal ultrasound: may show a “starry sky” appearance of the amniotic fluid, facilitating antenatal diagnosis.
- Aspirated amniotic fluid microscopy.
What is the differential diagnosis for ichthyosis prematurity syndrome?
The clinical appearance is unique but other inherited skin conditions may need consideration, such as:
- Bullous ichthyosiform erythroderma
- Non-bullous ichthyosiform erythroderma
- Collodion baby
- Harlequin ichthyosis.
What is the treatment for ichthyosis prematurity syndrome?
- Vernix can be gently removed with gauze and an emollient.
- Infants should be nursed in a high humidity incubator.
- Emollients and humectants can be used for the ichthyosis remaining after the neonatal period.
- Genetic counselling of the parents is required.
- Low dose dexamethasone has been advocated for respiratory complications.
- Temporary ventilatory support may be required.
What is the outcome for ichthyosis prematurity syndrome?
Subsequent pregnancies require expert obstetric care and ultrasound observation of the amniotic fluid. Affected babies should be delivered with ventilatory support available.
An affected individual may continue to have dry skin and follicular ichthyosis into adult life. There is a higher incidence of atopic conditions (asthma, eczema, and hay fever).