Multiple dermatologic rashes complicate psoriasis diagnosis

Ms. SA, aged 22 years, presented to the clinic with a burning, flaking, itchy, and blistering rash scattered around the body. She stated the rash had been present for several weeks.

She had not been treated with any prescription medications at the time of her first visit, although she had been using over-the-counter medications and moisturizers with very little relief.

The patient denied any recent illness. She stated no family members or close contacts had a similar rash, no recent changes in skincare, hair care, or laundry. Ms. SA denied any associated fever, chills, joint or muscle aches.

Physical exam

 Ms. SA was a healthy, thin Arabic female, aged 22 years, in mild distress due to physically scratching. Her skin was warm and dry with no evidence of open wounds. There were areas of papular rash and pink, xerotic patches on the chest, abdomen, lower back, flanks, and upper and lower extremities. Skin turgor was normal and finger and toenails do not appear to be affected. 

Treatment and progress

Ms. SA was seen by one of the physician assistants (PAs) in the office. She was diagnosed with eczema and given a class II topical corticosteroid (halcinonide 0.1% cream), to be used twice daily for three weeks to all areas affected by the rash.

At her follow up, three weeks later, the patient reported moderate improvement of the original rash, but now complained of new rash symptoms on her hands. The itching was worse at night and was not relieved by the class II topical corticosteroid.

The patient was seen by one of the physicians and given a diagnosis of dyshidrotic eczema of the hands. She was instructed to use gloves during any wet activities and given a class I topical corticosteroid (clobetasol 0.05% cream) to apply every day before noon and hydrocortisone acetate 1.9%/Iodoquinol 1% cream every night before bedtime for her hands.The patient was also instructed to reduce her shower water temperature, continue the halcinonide 0.1% cream on the active original eczema rash sites, and continue moisturizers at least twice daily.  

Again at her three-week follow up, the patient complained that her rashes had worsened and she could not sleep at night due to the itching. The PA prescribed hydroxyzine 10mg to be taken at night for the itching.

The patient was then started on narrowband ultraviolet light B (NB-UVB) therapy twice a week with continuation of clobetasol cream, as needed, for flares.

Ms. SA followed up two weeks after beginning her NB-UVB therapy with a complaint that the rash was not improving and the itching was not relieved. A 4mm punch biopsy of the rash had been taken at that time because she had been seen by two other providers in the office and had not experienced relief of her symptoms despite treatment for two months.

The pathology revealed a diagnosis of confluent and reticulated papillomatosis, for which she was given a class I topical corticosteroid spray, desoximetasone 0.25%  spray (Topicort) to be applied twice daily, doxycycline monohydrate  100mg (Monodox) to be taken orally twice daily, and levocetirizine dihydrochloride 5mg (Xyzal) to be taken orally at bedtime.

The patient’s rash was improved at the two-week follow up, but was still active. Ciclopirox cream 0.77% was added to her regimen. The patient was instructed to follow up in two weeks, but did not return to the office for nearly six weeks.

During that visit, the patient reported her rash had resolved so she didn’t feel a need to return. She had only returned because of a new rash that had developed on her chest, flanks, and lower back. She stated that it was similar to the rash that she first presented with.

Physical exam

Ms. SA was still a very pleasant, well developed, thin Arabic female, aged 22 years, in no acute distress. Her skin is warm and dry with no evidence of open wounds. There were very well demarcated patches on her center chest, bilateral flanks, and center lower back. The patches were slightly papular and erythematous with evidence of scaling. There were no other signs of rash on her body.

A 4mm punch biopsy was taken from the lower back and right flank to determine the histology of the new rash. The result given two weeks later was consistent with psoriasis. She was continued on desoximetasone 0.25%  spray for two weeks.

Incidentally, at the next follow up, the patient also complained of increased itching since her last visit, especially at night, all over her body, but especially her feet. The patient revealed multiple excoriated papules and small fissures on her feet in the web spaces, to which a scabies oil prep slide was performed immediately.

The slide revealed a scabies mite with unexpelled ova. The patient, as well as her family, was treated with 5% permtherin cream two applications one week apart. She was counseled on the proper hygiene and cleaning techniques for her home and family, and asked to follow up in two weeks.

At her follow up, the patient was clear. Her psoriasis was well-controlled using desoximetasone 0.25% spray as needed for active plaques.

Discussion

Confluent and reticulated papillomatosis (CRP) was first described in 1927, by Gougerot and Carteaud. The etiology is unknown, but is thought to be an inappropriate reaction to fungi on the skin.

It usually affects young people and appears as a dusky, sometimes velvety papular rash that coalesces into a plaque on the neck and trunk. The edges of the plaques sometimes appear reticular. The rash can appear hypopigmented in darker Fitzpatrick skin types, which can be misdiagnosed as tinea versicolor.

The rash in this case appeared slightly erythematous and was mistaken for eczema. An oral antibiotic with topical retinoids is usually the treatment of choice, but no therapy has been considered the gold standard.

In the case of Ms. SA, a biopsy confirmed the diagnosis and she was eventually treated with doxycycline, which helped to clear most of her rash, and then later an antifungal was added with complete success. Although CRP does not usually present with pruritus, Ms. SA was treated with topical corticosteroid, as well as an antihistamine for the itch.

There is a genetic predisposition in patients with eczema or atopic dermatitis. These patients have a defect in their adaptive and innate immunity. Their immune response is inappropriately hyper-responsive to environmental stimuli causing the skin barrier to be defective, thus resulting in increased epidermal water loss and a scaly appearance.

This defect in the barrier also makes an atopic patient more susceptible to bacterial and viral infections, increasing the inflammatory response causing the erythema that is most commonly described in eczematous rashes.

Psoriasis can present as thin, scaly, non-descript, erythematous patches and plaques, which can also be misdiagnosed as eczema, but histologically psoriasis is described as a parakeratotic dermatosis versus a spongiotic dermatosis description of eczema. Although both eczema and psoriasis are immune-mediated inflammatory skin disorders, biopsy should be performed to distinguish between the two if there is uncertainty.

An accurate diagnosis of psoriasis is important in patients who may be at risk for arthritic changes. The use of biologics and systemic medications may be necessary early in therapy to prevent damage to the joints. Ms. SA did not have joint pain complaints. Her therapy was strictly topical and was successful.

Scabies is an infestation of microscopic mites, which burrow into the skin laying eggs along the way. A common complaint in a patient with scabies is increased itching at night. Ms. SA had this complaint early in her therapy, however multiple dermatoses also present with nocturnal itch.

An early presentation of scabies may also present similar to an eczema rash. Treatment with topical corticosteroids can delay diagnosis of scabies as they may decrease the presentation of excoriated papules and burrows. Scabietic nodules are a late presentation and are often found in the web spaces of the hands and feet. A scabies mite, ova, or stool detected on an oil prep slide is an obvious a positive indication of a scabies infestation, however, mites are not commonly identified on an oil prep slide.

There are multiple reasons a slide might be negative — either the skin scraping is too superficial, or the mite may have moved on. Positive or negative slide aside, the decision for treatment is often determined based on clinical suspicion.

The most common treatment is permethrin 5% cream applied from neck to feet for 8 to 14 hours to be repeated in a week. Ivermectin dosed at 0.2mg/kg as a single dose is another popular therapy because of the convenience of single dose. An important aspect of scabies treatment is patient education about personal and home hygiene. If the home is not cleaned, a recurrence of the infestation is likely.

Conclusion

Ms. SA may have originally presented with scabies that was missed, but in the treatment failures, there was also success in correctly diagnosing and treating two other rashes.

The dermatitis patient can be extremely complex in their presentation, as well as have multiple dermatoses complicating the diagnosis. It is important to remember to take a good history before you start your physical exam. Histories help in the accurate diagnosis of dermatoses. Consider a wide range of differentials and narrow your therapies as you narrow your differential range.

B. Jang Mi Johnson, PA-C, is the senior physician assistant at Illinois Dermatology Institute, specializing in surgical and general dermatology.