O26.43 Herpes gestationis, third trimester

Name of the Condition

• Herpes gestationis, third trimester
• ICD Code: O26.43

Summary

Herpes gestationis is a rare autoimmune blistering disorder that occurs during pregnancy, typically presenting in the third trimester. It is characterized by pruritic (itchy) papules and vesicles, primarily affecting the abdomen, trunk, and extremities. The condition is not related to herpes simplex virus but is linked to immune system changes during pregnancy. It usually resolves postpartum but may recur in subsequent pregnancies or with hormonal changes.

Causes

Herpes gestationis is an autoimmune disorder where the immune system produces antibodies targeting components of the skin, particularly the basement membrane zone. The exact trigger is unclear, but it is associated with pregnancy-related hormonal shifts and may involve genetic predisposition. The condition is not infectious and does not result from viral infection.

Risk Factors

Risk factors include a personal or family history of autoimmune diseases, such as thyroid disorders or celiac disease. Women with a history of herpes gestationis in prior pregnancies are at higher risk of recurrence. The condition is more common in first pregnancies and may be associated with certain HLA (human leukocyte antigen) types.

Symptoms

Symptoms include intense itching (pruritus) followed by the development of red, raised papules or vesicles. The rash typically appears on the abdomen, trunk, or extremities and may spread to other areas. Blisters may rupture, leading to secondary infection or scarring in severe cases.

Diagnosis

Diagnosis is based on clinical presentation, including the characteristic rash and timing during pregnancy. Skin biopsy and direct immunofluorescence testing may confirm the presence of complement C3 deposits along the basement membrane zone, supporting the autoimmune etiology.

Treatment Options

Treatment focuses on symptom relief and preventing complications. Topical or systemic corticosteroids are commonly used to reduce inflammation and itching. Antihistamines may help manage pruritus. In severe cases, immunosuppressive agents or plasmapheresis may be considered. Close monitoring of maternal and fetal health is essential.

Prognosis and Follow-Up

The condition usually resolves postpartum, but symptoms may persist for weeks or months. Recurrence in future pregnancies is possible, often with similar or more severe presentations. Regular follow-up is recommended to monitor for complications and adjust treatment as needed.

Complications

Potential complications include secondary bacterial infection from ruptured blisters, scarring, and preterm labor in rare cases. Fetal outcomes are generally favorable, but neonatal blistering has been reported in a small percentage of cases.

Lifestyle & Prevention

While prevention is not possible, managing symptoms and avoiding triggers (e.g., friction, heat) can reduce discomfort. Maintaining good skin hygiene and avoiding scratching may help prevent infection. Prenatal care and early intervention are key to minimizing risks.

When to Seek Professional Help

Seek medical attention if itching is severe, blisters appear, or the rash spreads rapidly. Prompt evaluation is necessary if signs of infection (e.g., pus, fever) or preterm labor occur. Healthcare providers can assess severity and adjust treatment to ensure maternal and fetal safety.

Tips for Medical Coders

Document the trimester (third trimester) and confirm the autoimmune nature of the condition. Ensure clinical notes specify the timing and characteristic rash to support accurate coding. Differentiate from other blistering disorders or infections to avoid miscoding.