History
A 56-year-old man presents to the dermatology out-patient clinic with a 2-year history of an asymptomatic eruption on his limbs. Lesions initially appeared on the dorsi of his hands, but over the past two years they have also appeared on his elbows and ankles. He is otherwise well.
Examination
He has an erythematous eruption consisting of grouped lesions on his hands, elbows and ankles. On the dorsi of his hands the lesions consist of discrete annular and polycyclic lesions with a raised erythematous edge and central clearing (Fig. 46.1). On palpation the lesions are indurated (firm thickening of the dermis) with no surface change such as xerosis or scaling (normal epidermis).
Questions
• What is the diagnosis?
• What is the underlying pathophysiology?
• What are the options for treatment?
Medicine
This man has a cutaneous eruption consistent with the diagnosis of granuloma annulare (GA). This is a relatively common skin eruption that can occur at any age. The asympto-matic lesions characteristically appear symmetrically on the dorsi of the hands and feet and over the flexor surfaces of the wrists and ankles. The onset of the lesions is usually insidious.
The morphology of GA is variable but characteristically there are multiple, grouped, small-diameter, annular erythematous lesions with a raised discrete edge. The centre of the lesions is usually mildly hyperpigmented compared with the surrounding normal skin.
Papules, nodules and plaques may also be seen. The skin lesions feel firm on palpation.Disseminated GA is a rare variant of the disease characterized by multiple papules on the trunk and limbs.
There is an increased incidence of GA in association with type 1 diabetes; therefore, test-ing of fasting blood glucose may be indicated if patients have any systemic symptoms.
The cause of GA remains unknown. Histopathology from affected skin is characterized by areas of degenerative collagen fibres surrounded by palisading granulomas and reactive giant cells. A granulomatous pathology has led to speculation of an infective aetiology. Treatment of GA is often unsatisfactory, however the eruption can resolve spontane-ously. Lesions can demonstrate a reverse Koebner’s phenomenon, whereby they resolve following damage though a skin biopsy or cryotherapy. Superpotent topical steroids with/ without occlusion for a few weeks may help lesions to disappear more quickly. For prob-lematic lesions over joints intra-lesional triamcinolone can be helpful. There are numer-ous case reports of other successful treatments including psoralen–UVA, photodynamic therapy, antibiotics, oral prednisolone and ciclosporin.
KEY POINTS
• Granuloma annulare is an asymptomatic eruption of unknown aetiology.
• Lesions are grouped characteristically over the dorsi of the hands and feet.
• The eruption usually resolves spontaneously, however treatment can be attempted to speed resolution.
need an explanation for this answer? contact us directly to get an explanation for this answer