SUN-635 - Insulin NPH-Induced Pityriasis Rubra Pilaris: A Rare Cutaneous Adverse Event

Background: Insulin therapy, particularly when initiated early in the course of diabetes, has significantly improved metabolic control and reduced the risk of long-term complications. However, insulin use may be associated with cutaneous adverse effects. The most frequently reported reactions include lipohypertrophy ,lipoatrophy, and transient allergic manifestations such as pruritus, erythema, and induration at injection sites. Rarely, more severe inflammatory dermatoses may occur. Recognition of cutaneous lesions can play a key role in both the initial diagnosis and the optimization of diabetes therapy. Pityriasis rubra pilaris (PRP) is a rare inflammatory keratinization disorder; drug-induced PRP is even more uncommon. It is classically characterized by hyperkeratotic follicular papules, waxy orange-red palmoplantar keratoderma, and generalized papulosquamous lesions with "islands of sparing". While most drug-associated cases are linked to targeted oncologic therapies (e.g., tyrosine kinase inhibitors), reports involving insulin therapy remain exceptionally rare.

Case presentation: We report the case of a 46-year-old woman with a 26-year history of diabetes mellitus and no chronic complications. Due to worsening glycemic control despite oral therapy, NPH insulin was initiated at a dose of 10 units daily. Five days later, she developed an acute, progressive, and intensely pruritic dermatosis with a cephalocaudal distribution. Physical examination revealed erythematous, scaly plaques involving the head and neck, upper trunk and proximal upper extremities. The presence of follicular papules on the extensor surfaces of the arms; waxy orange palmoplantar keratoderma; and the characteristic “nutmeg grater” sign on the fingers was noted. Skin biopsy demonstrated hyperkeratosis with focal parakeratosis at the follicular ostia and a superficial perivascular lymphohistiocytic infiltrate, consistent with PRP. Given the close temporal relationship with insulin initiation and symptom onset, NPH insulin was discontinued and replaced with insulin detemir, achieving adequate glycemic control. The patient was treated with high dose oral isotretinoin and topical clobetasol. The adverse event was reported to the National Pharmacovigilance Unit. Marked clinical improvement was observed within three months, and at six-month follow-up, the patient remains in complete remission on emollient therapy alone.

Conclusion: This case highlights a rare but potentially severe cutaneous adverse reaction associated with NPH insulin. Awareness of uncommon dermatologic manifestations of insulin therapy is essential, as early recognition and prompt modification of treatment can lead to favorable outcomes without compromising glycemic control.

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