Crusted scabies in a patient being treated with infliximab for juvenile rheumatoid arthritis

A systematic review of immunosuppressive risk factors and comorbidities associated with the development of crusted scabies

OBJECTIVES

Crusted scabies (CS, Norwegian scabies) is a severe form of scabies, characterized by hyper-infestation of Sarcoptes scabiei mites. CS is commonly associated with immunosuppression but is also reported in overtly immunocompetent individuals. We reviewed immunosuppressive risk factors and comorbidities associated with CS.

METHODS

The National Library of Medicine (PubMed) database was reviewed for patient case reports of CS from January 1998 to July 2023. Two authors screened records for eligibility, extracted data, and one critically appraised the quality of the studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023466126.

RESULTS

A total of 436 records were identified, of which 204 were included for systematic review. From these, 683 CS patients were included. CS impacted both genders equally. Adults (21-59 years) were more commonly affected (45.5%) compared to children (0-20 years, 21%). Corticosteroid use was the most prevalent immunosuppressive risk factor identified (27.7% of all cases). About 10.2% of reports were associated with HIV/AIDS, and 8.5% with HTLV-1 infection. 10.5% of patients were overtly immunocompetent with no known risk factors. Overall, 41 (6.0%) died, many subsequent to secondary bacteremia.

CONCLUSION

This study represents the first systematic review undertaken on immunosuppressive risk factors associated with CS. This provides insights into trends of immunosuppression and mechanisms of CS development.

Opportunistic tropical infections in immunosuppressed patients

Autoimmune and autoinflammatory diseases are associated with severe morbidity, and represent an impactful health and economic burden worldwide. The treatment of these diseases can include a course with detrimental side effects. Immunosuppression increases the risk of opportunistic infections, but in some cases, the abrupt discontinuation of these medications can result in immune reconstitution inflammatory syndrome. Special attention must be directed to endemic tropical infections, such as leishmaniasis, Chagas disease, malaria, arbovirosis, yellow fever, leprosy, paracoccidioidomycosis, disseminated strongyloidiasis, and ectoparasitosis. These endemic diseases of developing countries can be considered as possible emerging diseases in developed regions partially because of environmental factors and migration. In the present article, we aim to review the evidence-based aspects of the most important opportunistic tropical infections in immunosuppressed patients. We also aim to review the important aspects of vaccination, chemical prophylaxis, and treatment for these infections in people with medication-induced immunosuppression.

Risankizumab-Aggravated Crusted Scabies in a Patient with Down Syndrome

Risankizumab, an interleukin (IL)-23 antagonist, is a highly effective treatment for moderate to severe psoriasis. Crusted scabies (CS) is a rare and severe form of scabies, occurring mainly in immunosuppressed patients and/or neurologically or mentally ill patients. A young girl with Down syndrome was diagnosed with a hyperkeratotic form of psoriasis. As treatment with topical dermocorticosteroids, UVB-phototherapy and acitretin for 6 weeks did not improve the lesions, two injections of risankizumab were administered. Following these injections, the lesions became rapidly even more severely crusted, and new lesions appeared on the extremities and the face of the patient. There was histological evidence of a high charge of scabies, leading to a diagnosis of CS. The patient was hospitalized and successfully treated by local permethrine and systemic ivermectine. This case suggests that even though anti-IL23 antagonists display an excellent overall safety profile, a particular caution for infections should still be respected in patients with underlying risk factors.

Ectoparasites: Scabies

Scabies is an ectoparasitic dermatosis caused by Sarcoptes scabiei var. hominis and is a public health issue in all countries regardless of socioeconomic status. In high-income countries, delays in diagnosis can lead to institutional outbreaks; in low- and middle-income countries, poor access to health care contributes to disease undertreatment and long-term systemic sequelae. With scabies now recognized as a neglected tropical disease by the World Health Organization, increased awareness and systematic efforts are addressing gaps in diagnosis and treatment that impede scabies control. This review summarizes the available data and provides an update on scabies epidemiology, clinical features, diagnosis, management, and public health considerations.

European guideline for the management of scabies

Scabies is caused by Sarcoptes scabiei var. hominis. The disease can be sexually transmitted. Patients' main complaint is nocturnal itch. Disseminated, excoriated, erythematous papules are usually seen on the anterior trunk and limbs. Crusted scabies occurs in immunocompromised hosts and may be associated with reduced or absent pruritus. Recommended treatments are permethrin 5% cream, oral ivermectin and benzyl benzoate 25% lotion. Alternative treatments are malathion 0.5% aqueous lotion, ivermectin 1% lotion and sulphur 6-33% cream, ointment or lotion. Crusted scabies therapy requires a topical scabicide and oral ivermectin. Mass treatment of large populations with endemic disease can be performed with a single dose of ivermectin (200 micrograms/kg of bodyweight). Partner management needs a look-back period of 2 months. Screening for other STI is recommended. Patients and close contacts should avoid sexual contact until completion of treatment and should strictly observe personal hygiene rules when living in crowded spaces. Written information should be provided to suspected cases.

Large Nosocomial Outbreak Associated with a Norwegian Scabies Index Case Undergoing TNF-α Inhibitor Treatment: Management and Control

We describe a large outbreak associated with a crusted (Norwegian) scabies case in an immunocompromised patient following treatment with TNF-α inhibitor (adalimumab) for psoriasis arthritis. The increasing use of TNF-α inhibitors should induce clinicians to consider this serious parasitic infection when evaluating skin rashes in patients receiving biologic therapies.

Development of Conventional and Real-Time Quantitative PCR Assays for Diagnosis and Monitoring of Scabies

Scabies remains the most prevalent, endemic, and neglected ectoparasitic infestation globally and can cause institutional outbreaks. The sensitivity of routine microscopy for demonstration of Sarcoptes scabiei mites or eggs in skin scrapings is only about 50%. Except for three studies using conventional or two-tube nested PCR on a small number of cases, no systematic study has been performed to improve the laboratory diagnosis of this important infection. We developed a conventional and a real-time quantitative PCR (qPCR) assay based on the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of S. scabiei. The cox1 gene is relatively well conserved, with its sequence having no high levels of similarity to the sequences of other human skin mites, pathogenic zoonotic mites, or common house dust mite species. This mitochondrial gene is also present in large quantities in arthropod cells, potentially improving the sensitivity of a PCR-based assay. In our study, both assays were specific and were more sensitive than microscopy in diagnosing scabies, with positive and negative predictive values of 100%. The S. scabiei DNA copy number in the microscopy-positive specimens was significantly higher than that in the microscopy-negative specimens (median S. scabiei DNA copy number, 3.604 versus 2.457 log10 copies per reaction; P = 0.0213). In the patient with crusted scabies, the qPCR assay performed on lesional skin swabs instead of scrapings revealed that the parasite DNA load took about 2 weeks to become negative after treatment. The utility of using lesional skin swabs as an alternative sample for diagnosis of scabies by PCR should be further evaluated.

Scabies

Scabies is an ectoparasite caused by the mite Sarcoptes scabiei var hominis, an obligate human parasite. There are about 300 million cases of scabies in the world each year. Common predisposing factors are overcrowding, immigration, poor hygiene, poor nutritional status, homelessness, dementia, and sexual contact. Direct skin-to-skin contact between 15 and 20 minutes is needed to transfer the mites from one person to another. The diagnosis suspected with a clinical history of itch, worse at night, affecting other family members, clinical distribution, and appearance. Definite diagnosis relies on microscopic identification of the mites, eggs, or fecal pellets with 10% potassium hydroxide, ink enhancement, tetracycline fluorescence tests, or mineral oil; other methods include: epiluminescence light microscopy and S. scabiei DNA. The most commonly used treatment modalities are permethrin and ivermectin. Persistence of symptoms for 2-6 weeks after successful treatment is common. Most recurrences are because of reinfection from untreated contacts.