Recurrent impetigo herpetiformis: case report

Impetigo herpetiformis (pustular psoriasis of pregnancy) is a rare dermatosis of pregnancy that typically starts in the 2nd half of pregnancy and resolves postpartum. It may recur in subsequent pregnancies. I present a case of 23 year old female gravida 4 para 3 with recurrent impetigo herpetiformis at 26 weeks gestation. She presented with a one month history of pustular lesions which responded to treatment with prednisone. She delivered at term with a favourable outcome. The disease resolved one month postpartum. This was the second recurrence of the disease. She had her first episode of impetigo herpetiformis during the second pregnancy. The disease recurred in the 3rd pregnancy and resulted in a still birth.


Introduction
Skin changes in pregnancy can be broadly divided into physiological, specific dermatoses of pregnancy, and other common skin diseases in pregnancy [1]. The specific dermatoses of pregnancy represent a heterogeneous group of severely pruritic inflammatory dermatoses associated exclusively with pregnancy or the immediate postpartum period [1]. Specific dermatoses of pregnancy are classified as: pemphigoid gestationis (herpes gestationis), pruritic urticarial papules and plaques of pregnancy, atopic eruption of pregnancy (eczema in pregnancy, prurigo of pregnancy, pruritic folliculitis of pregnancy) and pustular psoriasis of pregnancy (Impetigo herpetiformis).
Impetigo herpetiformis (pustular psoriasis of pregnancy) is a variant of pustular psoriasis, a specific dermatosis that occurs in pregnancy with the onset being in the 3rd trimester in majority of the cases.
The condition was first reported by Ferdinand Ritter von Hebra in 1872. In his report, von Hebra [2] reported five cases of pregnant women with pustular lesions. All the cases had fetal death and four of the five women died. Impetigo herpetiformis is an extremely rare condition. It is clinically and histologically similar to pustular psoriasis. There has been a debate on whether pustular psoriasis of pregnancy is a separate disease entity or a pustular stage of generalized pustular psoriasis occurring in pregnancy [3]. It is assumed by some authors to be a simple variant of generalized pustular psoriasis, representing a pustular stage of the disease, as a result of the hormonal changes of pregnancy or other factors that are not yet understood. However the authors have emphasized the need to consider this condition as a separate entity from generalized pustular psoriasis [4].
The underlying aetiology and specific pathogenesis of impetigo herpetiformis is largely unknown. The condition occurs in pregnancy in women who often have no history of pustular psoriasis. It is clinically manifested as erythema and pustular eruptions (usually without pruritus) and resolves postpartum. The disease is associated with placental insufficiency with sequelae such as miscarriage, fetal distress, fetal growth restriction, and stillbirths. Recurrence in subsequent pregnancies is common. Obstetric ultrasound yielded normal findings. The patient was admitted for inpatient management. Laboratory investigations were conducted. Evaluation of blood slide for malaria parasite was done but found negative. A rapid HIV antibody test was done and she was found negative. A complete blood count was also done. The hemoglobin was 11.6 g/dl. White blood cell count was elevated at

Discussion
Impetigo herpetiformis is a dermatosis of pregnancy that clinically and histologically resembles generalized pustular psoriasis. It is a rare dermatosis with potential serious consequences for mother and the child. It tends to occur in the third trimester of pregnancy, although cases have been reported as early as the first trimester [5]. In this case, patient's symptoms developed in the second trimester of pregnancy. Recurrence in subsequent pregnancies has been reported. In such cases, the disease tends to be more severe and occur at an earlier gestation, as was the case in our patient.
Following resolution, flares have been reported postpartum, during menses and on use of oral contraceptives. The aetiology and pathogenesis of impetigo herpetiformis is not completely understood but may be related to hormonal changes in pregnancy, particularly progesterone. Hypocalcemia and hypoparathyroidism are considered to be aggravating factors.
Classically, impetigo herpetiformis is characterized by sterile pustules initially arising from intertriginous areas of the body, with subsequent involvement of the trunk and limbs. Some lesions may coalesce into large pus-filled bullae. The lesions are usually not pruritic as was the case in our patient. The patients may also have constitutional symptoms such as fever and generalized body malaise. The symptoms such as nausea, vomiting, dehydration, diarrhea, chills and convulsions have also been reported but these were absent in our patient [6,7].
Hypocalcemia may be related to hypoparathyroidism [8]. The reported patient had leukocytosis, neutrophilia, and hypoalbuminemia. Although the significance of histopathological examination of skin and placenta is not specified clearly, it may be useful in the diagnosis of this condition [9]. The histopathology of impetigo herpetiformis is similar to that of pustular psoriasis. The characteristic finding in an early lesion is the presence of collections of polymorphonuclear neutrophils in spongiotic foci in the epidermis, known as spongiform pustules of Kogoj [5].
Impetigo herpetiformis has been associated with poor pregnancy outcomes including miscarriages, premature rupture of membranes, still births and intrauterine growth restriction [10][11][12] Corticosteroids should be slowly tapered as the patient responds to treatment. Although our patient was treated successfully with prednisone, some unresponsive cases to prednisone have been reported [13][14][15]. Successful treatment with cyclosporine has been reported and this regime can be used as second line treatment [6,16,17]. Antibiotics may be used to prevent and treat infections. It is reported that taking parenteral calcium, vitamin D, infliximab and Page number not for citation purposes 4 pyridoxine in high doses, as well as chorionic gonadotropin, is effective for impetigo herpetiformis during pregnancy [9]. Taking methotrexate, retinoids (such as acitretin) and ultraviolet A (PUVA) may be helpful for treatment of impetigo herpetiformis after delivery [12,[18][19][20].

Conclusion
The case had classical features of impetigo herpetiforms. The symptoms of this condition start in pregnancy and resolve postpartum, with risk of recurrence in subsequent pregnancies. The affected pregnancies may have bad outcomes such as stillbirths.
Majority of patients respond to corticosteroid treatment and this should be used as first line in patients with impetigo herpetiformis.
The affected patients should be followed up in subsequent pregnancies to observe for recurrence.