Granuloma annulare — SAQ

Stem

A 28-year-old woman presents with a 6-month history of an asymptomatic, slowly expanding ring of small, firm, skin-coloured papules on the dorsum of her left hand. The ring has a smooth, raised border with central clearing. The surface is non-scaly. She is otherwise well with no systemic symptoms, joint pain or drug history. A skin biopsy is performed and shows a palisading granuloma with central necrobiotic collagen and mucin deposition.

Questions

a) What is the most likely diagnosis and what clinical features support it? (2 marks)

b) What is the key histological finding and how does it help distinguish this condition from sarcoidosis and necrobiosis lipoidica? (3 marks)

c) Outline your management plan for this patient. (3 marks)

d) If the patient had 50 similar lesions on her trunk and extremities, what additional investigations would you consider and why? (2 marks)

Model answer

a) Diagnosis and clinical features (2 marks)

Most likely diagnosis: localized granuloma annulare (GA). (1 mark)^[1]

^[1][3]Clinical features supporting the diagnosis:

• Annular ring of small, firm, skin-coloured papules with a smooth, raised border and central clearing.
• Site on the dorsum of the hand, which is classic for localized GA.
• Non-scaly surface distinguishing it from tinea corporis and annular psoriasis.
• Asymptomatic and slowly progressive.
• Young adult patient — typical demographic for localized GA. (1 mark)

^[2]

b) Histology and differential diagnosis (3 marks)

Key histological finding: palisading granuloma with central necrobiotic collagen and mucin deposition surrounded by palisading histiocytes. (1 mark)^[1]

Distinguishing features:^[2]

• Sarcoidosis: shows naked, non-caseating granulomas with no mucin and no necrobiosis. (1 mark)
• Necrobiosis lipoidica: shows layered/horizontal granulomatous inflammation extending across the entire dermis, with plasma cells, thickened vessels and no mucin. (1 mark)

c) Management plan (3 marks)

• Reassurance and observation are appropriate because localized GA is usually self-limiting, commonly resolving spontaneously within months to years. (1 mark)
• If treatment is desired for cosmetic or symptomatic reasons, first-line options include potent topical corticosteroids (short course, with occlusion for thick lesions) or intralesional triamcinolone injected into the active border. (1 mark)
• Other options include cryotherapy, topical tacrolimus or topical pimecrolimus, especially on steroid-sensitive sites. (1 mark)

^[1]

d) Additional investigations if generalized disease (2 marks)

If the patient had widespread lesions, this would suggest generalized GA. Additional investigations would include:

• Fasting plasma glucose and HbA1c to screen for diabetes mellitus. (0.5 mark)
• Lipid profile to screen for dyslipidaemia. (0.5 mark)
• Thyroid function tests (TSH, free T4) to screen for thyroid disease. (0.5 mark)
• HIV test if risk factors, and age-appropriate malignancy screening if the patient is older or has systemic symptoms. (0.5 mark)

^[1]

References3ShowHide

1. [1]Joshi TP, Duvic M. Granuloma Annulare: An Updated Review of Epidemiology, Pathogenesis, and Treatment Options Am J Clin Dermatol, 2022.PMID 34495491
2. [2]Trayes KP, Savage K, Studdiford JS. Annular Lesions: Diagnosis and Treatment Am Fam Physician, 2018.PMID 30216021
3. [3]Joshi TP, Duvic M. Granuloma Annulare: An Updated Review of Epidemiology, Pathogenesis, and Treatment Options Am J Clin Dermatol, 2022.PMID 34495491