What is psoriasis?
Psoriasis is a chronic inflammatory skin condition usually characterised by well-demarcated red and scaly plaques on typical parts of the body including the knees, elbows, and lower back.
It can occur on any part of the body and different types of psoriasis are recognised. Pustular psoriasis of pregnancy (impetigo herpetiformis) is a rare variant of pustular psoriasis, usually occurring in the third trimester.
Psoriasis in pregnancy
Psoriasis is common in women of reproductive age as three-quarters of patients develop the disease before reaching their 4th decade. It tends to persist lifelong and will generally fluctuate in severity.
For many pregnant women (33–60%), psoriasis improves during pregnancy but for a minority the disease may flare (25%). In the postpartum period, flaring of psoriasis is common (65%).
The severity of psoriasis during pregnancy can improve during pregnancy (40–60%), worsen (10–20%), or remain stable in the remainder.
What are the clinical features of psoriasis in pregnancy?
There are no differences in the clinical features of psoriasis during pregnancy apart from the variation in severity for the individual woman pre-, during, and post-pregnancy.
See Psoriasis for more information.
How do clinical features vary in differing types of skin?
Plaque psoriasis is the most common type of psoriasis in all racial groups.
- Non-Caucasians tend to have more extensive skin involvement than Caucasians.
- Asian populations are reported to have the highest percentage of body surface area involvement.
- In skin of colour:
- Plaques are typically thicker with more pronounced silver scale and itch
- Pinkness of early patches may be more difficult to recognise resulting in a low PASI assessment
- Thick plaques may appear violet or dark in colour
- Plaque psoriasis commonly resolves to leave hyper- or hypopigmentation which may further impact quality of life even after disease clearance.
What are the complications of psoriasis in pregnancy?
- Pustular psoriasis of pregnancy (impetigo herpetiformis)
What is the treatment for psoriasis in pregnancy?
Some topical and systemic treatments may harm the baby, so care is needed. The effect of some treatments is unknown. Phototherapy is useful and there is increasing evidence for the use of biologics. Oral photochemotherapy (PUVA) has theoretical mutagenic risk, although detailed studies have not substantiated this, but it is best avoided in pregnancy
Topical treatments that could be considered include:
- Simple emollients appear to be safe during pregnancy
- Topical steroids used appropriately, depending on their potency
- Calcipotriol, but maternal vitamin D toxicity may have a risk of teratogenicity so small quantities are recommended
- Salicylic acid, but do not use high concentrations, large quantities, or cause occlusion as maternal systemic absorption is possible
- Calcineurin inhibitors (pimecrolimus and tacrolimus) used in small quantities.
Narrow band ultraviolet light (nUVB) is considered to be safe for pregnant patients. Phototherapy depletes folate so supplementation is recommended.
- Ciclosporin (cyclosporin) appears to be safe in pregnancy and is used for moderate to severe psoriasis.
- Acitretin must be avoided during pregnancy as it is highly teratogenic and avoided three years prior to conception.
- Methotrexate must be avoided during pregnancy as it is highly teratogenic and an abortifactant.
- Apremilast has not been studied in pregnancy and should not be taken.
There are no controlled studies of the use of biologics in pregnant patients. However, there is increasing evidence for the safe and effective use of biologics in moderate to severe psoriasis treatment during pregnancy. Stopping these agents during pregnancy carries a risk of moderate to severe psoriasis flaring. There is less data about some of the newer agents.
Many monoclonal antibodies used in the treatment of psoriasis actively cross the placental barrier especially in the third trimester after organogenesis is complete, resulting in therapeutic levels in the baby. However, certolizumab (a pegylated tumour necrosis alpha inhibitor), crosses the placental barrier passively and is present in negligible or low concentrations in the baby because of its molecular structure, which lacks an Fc moiety. Etanercept (fusion protein including the Fc receptor) is also present in infants at low levels. If it is safe to do so, some dermatologists withhold the biological agent for the last 8 weeks of pregnancy so that infants are born with negligible levels of the administered drug.
Vaccination of infants
Great care needs to be taken with biologics that cross the placental barrier and vaccinating the newborn infant with live/attenuated vaccines including the Bacillus Calmette-Guérin (BCG) vaccine. There is significant potential for harm or death from live/attenuated vaccines in the infant who are immunocompromised due to them having therapeutic levels of the biological agent that their mother is receiving. There are stand down periods in which the infant must not be vaccinated with these agents; this is commonly 6 months or longer.
There are a number of new agents being developed for psoriasis including janus kinase (JAK) inhibitors and tyrosine kinase inhibitors. There is insufficient evidence to base a recommendation at present for their use in pregnancy and they should be avoided.
What is the outcome for psoriasis in pregnancy?
Many women will only need topical treatments. However, for those women who require systemic treatment such as those with extensive psoriasis, careful judgement needs to be exercised. A balance of the significant adverse effects of untreated psoriasis on maternal wellbeing and conception against the potential risk of systemic agent use must be sought.