Interstitial granulomatous drug reaction

A rare skin condition caused by drug reactions

Interstitial granulomatous drug reaction (IGDR) is a rare dermatological condition characterized by the formation of granulomas in the skin due to an adverse reaction to certain medications. This condition is part of a broader category of cutaneous drug reactions, which are skin manifestations resulting from drug exposure.

Pathophysiology

Interstitial granulomatous drug reaction is believed to be an immune-mediated response. The exact mechanism is not fully understood, but it involves the formation of granulomas, which are organized collections of macrophages, often with other immune cells such as lymphocytes and plasma cells. These granulomas form in the dermis, the layer of skin beneath the epidermis.

The reaction is thought to be triggered by certain medications, which may act as haptens or antigens, leading to an immune response. The immune system mistakenly targets the skin, resulting in inflammation and granuloma formation.

Clinical Presentation

Patients with interstitial granulomatous drug reaction typically present with erythematous (red) plaques or nodules on the skin. These lesions are often asymptomatic, but they can be pruritic (itchy) or tender. The distribution of the lesions can vary, but they are commonly found on the trunk and extremities.

Diagnosis

The diagnosis of IGDR is primarily clinical, supported by a detailed medical history and physical examination. A skin biopsy is often performed to confirm the diagnosis. Histopathological examination of the biopsy typically reveals interstitial granulomatous inflammation with histiocytes and lymphocytes in the dermis.

Differential Diagnosis

The differential diagnosis for interstitial granulomatous drug reaction includes other granulomatous skin conditions such as:

• Granuloma annulare
• Sarcoidosis
• Necrobiosis lipoidica
• Rheumatoid nodules

Management

The primary treatment for IGDR is the identification and discontinuation of the offending drug. Once the causative medication is stopped, the skin lesions often resolve spontaneously over weeks to months. In some cases, additional treatments may be necessary, including:

• Topical corticosteroids to reduce inflammation
• Systemic corticosteroids for more severe cases
• Antihistamines to alleviate itching

Prognosis

The prognosis for interstitial granulomatous drug reaction is generally good, especially if the offending drug is identified and discontinued promptly. Most patients experience complete resolution of skin lesions without long-term sequelae.

Related Pages

• Granuloma
• Drug reaction
• Cutaneous adverse drug reaction
• Immune system