P075 Skin as a window into inborn errors of immunity: comprehensive analysis of 539 immunodeficient patients with skin involvement

Abstract

Inborn errors of immunity (IEIs) are a heterogeneous group of genetic conditions that impair the development or function of the immune system. These disorders may present with a wide range of clinical features, among which cutaneous manifestations are common and often appear early in the disease course. This study aims to determine the frequency of various dermatological manifestations in patients with IEIs and to compare the most common skin findings in IEIs with those of the general population, potentially serving as early diagnostic indicators of IEIs. We reviewed demographic, clinical history and dermatological findings of patients with definite IEI from 2006 to 2025 in our IEI registry, retro­spectively. Diagnoses were classified according to the International Union of Immunological Societies, 2024 guidelines. Skin findings were categorized into four main categories. Of 1447 patients with confirmed IEI in our registry, 539 (37.2%, 95% confidence interval 34.7–39.7%) had cutaneous involvement, with a mean age at onset of 13.6 months (SD 11.7). Phagocytic defects and combined immunodeficiencies were the most frequent diagnoses. Cutaneous infections were observed in 73.6% of patients, most commonly bacterial (67.5%), including abscesses, bacille Calmette–Guérin-related complications, cellulitis and omphalitis. Nonclassified manifestations (38.0%) included suppurative lymphadenitis, ulcerative/necrotic lesions and erythroderma, while immunoallergic conditions (28.7%) were mainly eczema. Viral and fungal infections and syndromic markers, were rare. Over one-third of patients with an IEI exhibited cutaneous signs, highlighting the diagnostic value of dermatological assessment in suspected cases of immunodeficiency. Skin manifestations may serve as an early and accessible clue in the diagnosis of an IEI, warranting greater clinical attention.