Norwegian scabies presenting as erythroderma: A case report

Abstract

BACKGROUND

Norwegian scabies (NS) is a serious parasitic skin condition. Although NS is one of the causes of erythroderma, it is frequently overlooked. Therefore, it is essential to raise awareness regarding NS presenting as erythroderma.

CASE SUMMARY

We present a case of NS that persisted for more than 3 years. After following nonstandard treatment, the patient’s rash worsened and gradually progressed into erythroderma. Finally, NS was diagnosed by skin microscopy and pathology.

CONCLUSION

When patients with pruritic dermatosis have high-risk factors such as prolonged bed rest and immunodeficiency, clinicians need to enhance their awareness of NS and ensure prompt diagnosis and treatment.

Key Words: Norwegian scabies, Crusted scabies, Erythroderma, Diagnosis, Case report

Core Tip: In this study, we have described an elderly patient with Norwegian scabies for over 3 years. The patient developed multiple erythema, papules, and scales throughout the body. After repeated irregular treatments, his condition worsened for 2 months, and the rash advanced to diffuse infiltrating dark erythema with keratinized papules, pustules, and thick scales.

INTRODUCTION

Scabies is a parasitic skin disease caused by human scabies mites. Norwegian scabies (NS) is one of the most severe types of scabies. It is more frequent in patients who are physically weak, have weakened immune function, and have extremely poor personal hygiene. Unlike classic scabies, it is characterized by an excessive number of mites on the skin surface, which can affect the scalp, face, back, and nail wrinkles[1]. Erythroderma is often secondary to conditions such as dermatitis, psoriasis, lymphoma, and drug-induced dermatitis. Although NS is also one of the causes of erythroderma, it is frequently overlooked. Therefore, it is essential to raise awareness regarding NS presenting as erythroderma.

CASE PRESENTATION

Chief complaints

A 74-year-old man was admitted to the intensive care unit with a 1-day history of altered consciousness.

History of present illness

He had a history of generalized rash observed 3 years before admission and worsened 2 months before admission. Over 3 years ago, the patient developed scattered erythema and papules all over the body, accompanied by mild pruritus. The patient had been diagnosed with eczema and scabies, and was treated topically with corticosteroids and sulfur cream. However, the rash recurred and worsened 2 months ago, leading to severe erythroderma covering more than 90% of the body surface. Erythroderma due to eczema or psoriasis was considered as the first diagnosis. Although treatments such as anti-allergy, immune regulation, and external medicines were administered to repair the skin barrier, there was no significant improvement in his condition.

History of past illness

His medical history included hypertension, Parkinson’s disease, and left-sided hemiparesis resulting from cerebral infarction.

Personal and family history

We observed that two family members of the patient had a similar history of skin itching.

Physical examination

Generalized scaly erythema, papules-pustules over the whole body, and crusted hyperkeratotic lesions on the arms and hands, particularly the thick yellow scab on the palm (Figure 1A and B).

Figure 1 Clinical features and ancillary examinations of Norwegian Scabies. A and B: Diffuse erythema, scaly papules, and pustules on the trunk, and hyperkeratotic lesions on the arms; C: Scabies can be observed below the cuticle, with eosinophil, lymphocyte, and neutrophil infiltration in the superficial dermis (hematoxylin eosin staining); D: Microscopic examination showing scabies mites.

Laboratory examinations

Laboratory tests revealed an increase in eosinophils. Skin biopsy of the lesion was performed, and pathological examination showed a foreign body with encapsulated structures below the cuticle. Significant eosinophil infiltration in the superficial dermis, as well as moderate lymphocyte and neutrophil infiltration was noted (Figure 1C). Direct microscopy of skin scrapings revealed live scabies mites and eggs (Figure 1D).

FINAL DIAGNOSIS

The occurrence of NS was confirmed.

TREATMENT

After diagnosis, the patient was treated using 20% sulfur cream, resulting in an improvement in the rash.

OUTCOME AND FOLLOW-UP

Because of the patient’s primary disease and various complications, he eventually died of septic shock. Therefore, the prognosis and follow-up could not be conducted.

DISCUSSION

NS, also known as crusted scabies (CS), is a serious parasitic skin infection. The differential diagnosis of NS includes psoriasis, eczema, contact dermatitis, insect bites, seborrheic dermatitis, lichen planus, systemic infection, palmoplantar keratoderma, and cutaneous lymphoma[2]. Compared with conventional scabies, NS is typically characterized by generalized erythroderma and significant hyperkeratosis, which is easily misdiagnosed as erythrodermic psoriasis[3].

In this case, the patient had been experiencing a systemic rash for 3 years. Initially, “scabies” was considered, and the treatment provided temporary relief. However, he stayed in bed for a long time due to hemiplegia, and the rash progressed to generalized erythema, papules, pustules, scales, and scabs, and obvious thick scales and scabs could be observed at the fusion of trunk and hand and foot skin lesions. Therefore, after the first consultation in our department, the patient was misdiagnosed with eczema, psoriasis, and other skin diseases, which is similar to the previous studies. This underscores the common occurrence of misdiagnosis of NS in clinical practice. Due to the unsatisfactory treatment outcomes, a thorough review of the patient’s medical history was conducted, revealing that two family members had experienced rash and itching symptoms. This prompted the consideration of NS as a potential diagnosis. Factors for NS diagnosis are listed below: (1) The elderly patient who has been bedridden for an extended period, has multiple underlying diseases, and malnutrition. He has lived in a hot and humid place in southern China for a long time, providing favorable conditions for the parasites to thrive; (2) Two members of the patient’s family exhibit similar rash and itching symptoms; (3) The special rash all over the body; and (4) Itching, particularly at night, is prominent, and despite long-term use of anti-allergic medications and external application of glucocorticoid patches, there was no significant improvement.

The treatment of scabies typically involves the use of external medicine (chlorpyrifos, sulfur ointment, and lindane) and oral medicine (ivermectin). Although external sulfur ointment is no longer the primary treatment choice in developed countries[4], it is still widely used in treatment because of its advantages such as low price, simple preparation, and positive effect. In this case, the patient’s body rash improved after treatment with 20% sulfur ointment.

The patient’s hypoesthesia and lax treatment may have contributed to the treatment failure. Mechanical removal of mites and eggs by scratching is an effective host mechanism that can help limit their proliferation. Therefore, patients with cognitive impairment, physical disability, or neuropathy who cannot feel or interpret the itch or are unable to scratch effectively are at increased risk of developing CS[5]. Eventually, the condition progressed to erythrodermic scabies.

A previous study has revealed a significant delay in the diagnosis of NS[6]. Early identification enables appropriate management and treatment, thereby reducing the risk of infection and community-wide scabies outbreaks[7]. A delay in diagnosis and treatment results in the dissemination of the infestation with an increasing risk of sepsis and death, and scabies nosocomial outbreaks[8].

A patient with CS may host more than a million mites; therefore, scraping any affected site is highly likely to yield a definitive diagnosis[4]. As a result, the challenge of diagnosis is not the lack of evidence, but confirmation regarding the occurrence of NS. Awareness of this rare form of scabies should be raised among dermatologists, and when patients present with atypical psoriasis, atypical morbiliform eruptions, or erythroderma, NS should be considered[6].

CONCLUSION

Dermatologists should enhance their understanding of NS, perform thorough medical history inquiries, combine existing advanced diagnostic and treatment techniques for pathogen testing, clarify the diagnosis, and isolate and treat as early as possible to achieve early and precise treatment and effectively prevent epidemics within families or medical facilities.