A 64-year-old female presented with a two-week history of an itchy rash over her waist, wrist and fingers. 

The lady was a chronic diabetic, with higher-than-normal HbA1C. She also had a history of hypertension. She was on anti-hypertensives and oral hypoglycemic drugs.

On examination, the patient was afebrile with normal vital signs. Her skin revealed erythematous urticarial-like papules and plaques all over her waist and wrists. Burrows were identified on certain portions of her fingers.

Dermacosopy revealed the burrows and elicited the “jet with contrail” sign. In addition, non-necrotizing granulomas were observed within the dermis. 

Continued topical therapy and adequate preventive measures were taken to ward-off recurrence of the lesions. Complete symptom resolution could be achieved after 5 weeks.

Discussion

Scabies – a parasitic disease, is caused by Sarcoptes scabiei var. hominis. The disease is highly contagious and usually presents with dermal manifestations. Scabies affects approximately 150-200 million people worldwide and imposes a higher health-related burden in low-income countries and tropical areas. The disease is more common in among infants, children and adolescents. 

Scabies cause rash, which is often itchy. The dermal manifestations include – pruritic eruptions with burrows, papules or vesicles. The lesions can be categorized into three types – eruptions; red‐brown nodules; and burrows. Most patients also experience sleep disruption, difficulty with concentration and absenteeism from school or workplace. Scabies recurrence is common and the disease predisposes to bacterial skin infection and mixed infections.

The scabies burrow is the only pathognomonic feature, and is useful for definitive diagnosis. Scabies burrows are formed by mature female mites laying eggs through the stratum corneum. The eggs render the disease extremely contagious, especially through direct contact and fomites.

Evaluation of scabies is done through a detailed history and clinical examination of the skin. Investigations include microscopy using KOH and dermoscopy—which has a sensitivity rate of 91%. Scabies is often a clinical diagnosis. Other conditions, for example – psoriasis, atopic dermatitis, diaper dermatitis, allergic contact dermatitis and irritant contact dermatitis, must be ruled out before advising diagnostic tests.^1,2

Crusted scabies – also known as Norwegian scabies can occur in immunocompromised patients, and is characterized by millions of mites infesting a single individual. 

Scabies recurrence should be prevented via isolation of the patient and careful decontamination to ward to fomites after the therapeutic course is completed.³

Granulomatous reaction in scabies may be overlooked, hence, it is important to consider granulomatous dermatitis in the differential diagnosis of scabies. Granulomatous dermatitis – a common tissue reaction, is characterized by granulomatous inflammation of the skin and may manifest in an array of conditions. It can be infectious or non-infectious.

Histopathology aids in the diagnosis; however, different types of granulomas exhibit overlapping features. Hence, clinical correlation is essential. Management of the primary infection is the most important step in treating infectious granulomas. Topical steroids can be used only after confirmatory tests shows the absence of infection.^4,5

References

1. Ueda T, Katsura Y, Sasaki A, Minagawa D, Amoh Y, Shirai K. Gray-edged line sign of scabies burrow. J Dermatol. 2021;48(2):190-198. doi:10.1111/1346-8138.15650
2. Engelman D, Yoshizumi J, Hay RJ, et al. The 2020 International Alliance for the Control of Scabies Consensus Criteria for the Diagnosis of Scabies. Br J Dermatol. 2020;183(5):808-820. doi:10.1111/bjd.18943
3. Gilson RL, Crane JS. Scabies. [Updated 2021 Aug 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544306/
4. Kumbar R, Dravid N, Nagappa KG, Rokade C. Infectious Granulomatous Dermatitis at a Tertiary Care Centre in North Maharashtra: A Histopathological Study. J Clin Diagn Res. 2016;10(11):EC13-EC16. doi:10.7860/JCDR/2016/15436.8891
5. Granulomas. Healthdirect.gov.au. https://www.healthdirect.gov.au/granulomas#treated. Published 2021. Accessed January 5, 2022.