Peer Reviewed

Dermatologic Conditions

An Atlas of Lumps and Bumps: Part 8

Alexander K. C. Leung, MD1,2 —Series Editor • Benjamin Barankin, MD3 • Joseph M. Lam, MD4 • Kin Fon Leong, MD5

1Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada
2Alberta Children’s Hospital, Calgary, Alberta, Canada
3Toronto Dermatology Centre, Toronto, Ontario, Canada
4Department of Pediatrics and Department of Dermatology and Skin Sciences, University of British Columbia, Vancouver, British Columbia, Canada
5Pediatric Institute, Kuala Lumpur General Hospital, Kuala Lumpur, Malaysia

Leung AKC, Barankin B, Lam JM, Leong KF. An atlas of lumps and bumps, part 8. Consultant. 2021;61(9):e25-e27. doi:10.25270/con.2021.08.00008

Dr Leung is the series editor. He was not involved with the handling of this paper, which was sent out for independent external peer review.

Alexander K. C. Leung, MD, #200, 233 16th Ave NW, Calgary, AB T2M 0H5, Canada (

This article is part of a series describing and differentiating dermatologic lumps and bumps. To access previously published articles in the series, visit


Prurigo Nodularis

Prurigo nodularis is a chronic inflammatory dermatosis characterized by multiple intensely pruritic, lichenified or excoriated papulonodules chiefly located on the posterior surfaces of the extremities, often triggered by severe and refractory pruritus.1 This condition occurs mainly in adults, with a peak between age 51 and 65 years.1,2 Patients with an atopic diathesis have a much earlier age of onset.3-5 Dark-skinned individuals are more commonly affected.1,2,6 There is a female predominance.1,2 Pruritic dermatological diseases that may predispose to prurigo nodularis include atopic dermatitis (most common), nummular eczema, contact dermatitis, scabies, lichen planus, psoriasis, xerosis, dermatitis herpetiformis, linear immunoglobulin A disease, and bullous pemphigoid.2,7-9 Atopic predisposition is a major factor in approximately 50% of patients with prurigo nodularis.7-9 Systemic diseases associated with prurigo nodularis include hepatic dysfunction, chronic renal failure, chronic obstructive pulmonary disease, thyroid dysfunction, cardiovascular disease, cerebrovascular disease, polycythemia rubra vera, inflammatory bowel disease (eg, Crohn disease, ulcerative colitis), type 2 diabetes, malignancy (eg, leukemia, lymphoma, gastrointestinal carcinomas), infections (eg, HIV, hepatitis B virus, hepatitis C virus, Helicobacter pylori, mycobacteria, Strongyloides stercoralis), parasitic infestation, and psychosocial disorders (eg, emotional stress, anxiety, depression, obsessive compulsive disorder).6-11 It is generally believed that chronic mechanical scratching and/or rubbing as a result of pruritus leads to the development of papulonodular or plaque-like lesions, which may be excoriated, crusted, and lichenified.1,3

Patients with prurigo nodularis often present with a long-standing history (≥ 6 weeks) of severe unremitting pruritus in the affected area, followed by the appearance of pruritic papulonodules.3,6,12 Clinically, papulonodules are multiple, firm, hyperkeratotic, and dome-shaped found mostly on extensor surfaces of the upper and lower extremities, followed by the trunk (Figures 1 and 2).1,2 The lesions can be flesh-colored, erythematous, or hyperpigmented.1 There is a tendency for symmetrical distribution. A linear arrangement of lesions is common. The size of an individual lesion ranges from a few millimeters to 3 cm in diameter.1,2,5,8,9 The number of nodules can range from a few to hundreds.8,9 Some of the lesions may be excoriated, crusted, or lichenified, pointing to ongoing scratching (Figure 3).8,9 Lichenoid plaques are also a frequent finding.8,9 The palms, soles, and face are rarely affected.5 The mid-back is often spared because it is difficult to reach, a finding known as the "butterfly sign" (Figure 4).5,7

Figure 1 Prurigo Nodularis
Figure 1.

Figure 2 Prurigo Nodularis
Figure 2. 

Figure 3 Prurigo Nodularis
Figure 3.

Figure 4 Prurigo Nodularis
Figure 4.


Pruritus is usually severe and confined to the lesions themselves. It can be constant, intermittent, or paroxysmal and may be accompanied by a stinging or burning sensation.6 The pruritus is often worsened by sweating, irritation from clothing, or heat.1 Alterations in lesional temperature have been reported.1 New lesions may develop from time to time, while some existing lesions may occasionally regress spontaneously. The skin between the lesions is usually normal but can be xerotic or lichenified. Excoriated lesions are at increased risk of secondary infection.1

Prurigo nodularis is a chronic debilitating disease that can lead to sleep and psychosocial disturbances.6 The condition may cause a profound negative impact on quality of life.6 The diagnosis is clinical and based on a long-standing history (≥ 6 weeks) of severe unremitting pruritus; history of repeated scratching, picking, or rubbing; and subsequent development of pruritic, excoriated, symmetrically distributed, papulonodular lesions in a vicious itch-scratch cycle.6,8,9 The diagnosis can be aided by dermoscopy and biopsy if necessary. Typical dermoscopic features include peripheral striations, pearly white area with starburst pattern, gray-blue globules, comedo-like openings, glomerular vessels, red dots and globules, brownish-black globules and yellow structures, crusting, and erosions.13,14

Nodular Scabies

Human scabies is an infestation of the skin caused by an obligate human parasite mite, Sarcoptes scabiei var. hominis.15,16 Classic scabies (common scabies) typically manifests as an intensely pruritic eruption with a characteristic distribution pattern.15,16 Nodular scabies, a less common clinical variant of scabies, is characterized by extremely pruritic, erythematous, firm, nodules that persist even after adequate treatment of the initial scabietic infestation (Figure 5).15-20 The pruritus is most intense at night.21 Nodular scabies occurs in approximately 7% of patients with scabies and is more common in men.22,23 Sites of predilection include the penis, scrotum, groin, buttocks, and axillary folds.22-24 These nodules do not contain live mites and do not indicate an active infestation.16,25,26 Rather, they represent a delayed type IV hypersensitivity reaction to retained mite parts, eggs, and/or fecal pellets (scybala) of a prior or current infestation.18-20,26 Some researchers propose that the condition may also be due to a deeper penetration of the mite from the epidermis into the dermis, resulting in a more vigorous inflammatory response.27

Figure 5 Nodular Scabies
Figure 5.



1. Mullins TB, Sharma P, Riley CA, Sonthalia S. Prurigo Nodularis. In: StatPearls. StatPearls Publishing; September 15, 2020.

2. Huang AH, Williams KA, Kwatra SG. Prurigo nodularis: Epidemiology and clinical features. J Am Acad Dermatol. 2020;83(6):1559-1565.

3. Amer A, Fischer H. Prurigo nodularis in a 9-year-old girl. Clin Pediatr (Phila). 2009;48(1):93-95.

4. Tan WS, Tey HL. Extensive prurigo nodularis: characterization and etiology. Dermatology. 2014;228(3):276-280.

5. Vaidya DC, Schwartz RA. Prurigo nodularis: a benign dermatosis derived from a persistent pruritus. Acta Dermatovenerol Croat. 2008;16(1):38-44.

6. Williams KA, Roh YS, Brown I, et al. Pathophysiology, diagnosis, and pharmacological treatment of prurigo nodularis. Expert Rev Clin Pharmacol. 2021;14(1):67-77.

7. Iking A, Grundmann S, Chatzigeorgakidis E, Phan NQ, Klein D, Ständer S. Prurigo as a symptom of atopic and non-atopic diseases: aetiological survey in a consecutive cohort of 108 patients. J Eur Acad Dermatol Venereol. 2013;27(5):550-557.

8. Zeidler C, Yosipovitch G, Ständer S. Prurigo nodularis and its management. Dermatol Clin. 2018;36(3):189-197.

9. Zeidler C, Tsianakas A, Pereira M, Ständer H, Yosipovitch G, Ständer S. Chronic prurigo of nodular type: a review. Acta Derm Venereol. 2018;98(2):173-179.

10. Dazzi C, Erma D, Piccinno R, Veraldi S, Caccialanza M. Psychological factors involved in prurigo nodularis: a pilot study. J Dermatolog Treat. 2011;22(4):211-214.

11. Fostini AC, Girolomoni G, Tessari G. Prurigo nodularis: an update on etiopathogenesis and therapy. J Dermatolog Treat. 2013;24(6):458-462.

12. Elmariah S, Kim B, Berger T, et al. Practical approaches for diagnosis and management of prurigo nodularis: United States expert panel consensus. J Am Acad Dermatol. 2021;84(3):747-760.

13. Hanumaiah B, Joseph JM. Role of dermoscopy in the diagnosis of hypertrophic lichen planus and prurigo nodularis. Indian J Dermatol. 2019;64(5):341-345.

14. Nair PA, Patel T. Dermatoscopic features of prurigo nodularis. Indian Dermatol Online J. 2019;10(2):187-189.

15. Leung AKC, Barankin B, Hon KL-E. What is this extremely pruritic rash with nighttime intensity? Consultant Pediatr. 2016;15(12):613-616.

16. Leung AKC, Lam JM, Leong KF. Scabies: a neglected global disease. Curr Pediatr Rev. 2020;16(1):33-42.

17. Lu Y, Qi X, Zhou X, et al. Intralesional botulinum toxin A injection for treating nodular scabies. Dermatol Ther. 2020;33(6):e14163.

18. Ramachandra Reddy D, Ramachandra Reddy P. Nodular scabies: a classical case report in an adolescent boy. J Parasit Dis. 2015;39(3):581-583.

19. Tai DBG, Abu Saleh O, Miest R. Genital nodular scabies. IDCases. Published online September 3, 2020.

20. Yanes DA, Faith EF. Nodular scabies: a persistent nodular eruption. Dermatol Online J. 2018;24(8):13030/qt5xd8t1t3.

21. Chandler DJ, Fuller LC. A Review of scabies: an infestation more than skin deep. Dermatology. 2019;235(2):79-90.

22. Daye M, Temiz SA, Kılınç F. A case of nodular scabies with atypical course. Dermatol Ther. 2020;33(3):e13317.

23. Manjhi M, Yadav P, Mohan S, Sonthalia S, Ramesh V, Kashyap V. A comparative study of topical tacrolimus and topical triamcinolone acetonide in nodular scabies. Dermatol Ther. 2020;33(6):e13954.

240. Sunderkötter C, Feldmeier H, Fölster-Holst R, et al. S1 guidelines on the diagnosis and treatment of scabies - short version. J Dtsch Dermatol Ges. 2016;14(11):1155-1167.

25. Hicks MI, Elston DM. Scabies. Dermatol Ther. 2009;22(4):279-292.

26. Shimose L, Munoz-Price LS. Diagnosis, prevention, and treatment of scabies. Curr Infect Dis Rep. 2013;15(5):426-431.

27. Tesner B, Williams NO, Brodell RT. The pathophysiologic basis of scabietic nodules. J Am Acad Dermatol. 2007;57(2 Suppl):S56-S57.