Autosomal recessive congenital ichthyoses (ARCI) are monogenic diseases of cornification that correspond to a diffuse abnormality (affecting the entire integument) of epidermal differentiation and therefore of the skin barrier. They manifest as abnormal desquamation (scaling) associated with varying degrees of inflammation (erythema). Around ten genes are currently implicated in ARCI. Nipal 4 is one of these genes, and mutations in it are found in around 1/10 of genotyped ARCI patients.

As part of this follow-up, three Nipal4 ARCI (Nipal4-nEDD) patients followed by the dermatology department of Saint-Louis hospital (Paris) were diagnosed with Sezary syndrome, a rare and serious cutaneous lymphoma (incidence 1/10,000,000), in adulthood (aged 30, 46, and 82). This lymphoma was diagnosed following a change in skin phenotype with worsening erythema, pruritus, and hyperkeratosis. The occurrence of two very rare diseases ( Nipal4-nEDD) and Sezary syndrome) in three patients raises the question of a non-coincidental association. The diagnosis of Sézary syndrome is based on a specific pathological circulating lymphocyte phenotype and is confirmed by skin histology. There is currently no obvious pathophysiological explanation for the concomitant occurrence of these two skin diseases. The blood lymphocyte phenotype of Nipal 4-nEDD patients without Sezary syndrome (SS) is unknown. A first step in investigating the mechanisms that could explain such an association would be to document this baseline lymphocyte phenotype in the Nipal 4-nEDD population without known SS.

Inclusion Criteria:

• Adult patients (> 18 years old)
• ARCI-type ichthyosis with NIPAL4 mutation (Nipal4-nEDD)

Exclusion Criteria:

• Ichthyosis that has not been genotyped or with mutations in different genes
• Patients with concomitant inflammatory, infectious, or hematological conditions
• Individuals subject to legal protection measures or deprived of their liberty by judicial or administrative decision
• Individuals under guardianship/curatorship
• Opposition to the research

Adult patients (M/F) with autosomal recessive congenital ichthyoses mutated NIPAL4 (Nipal4-nEDD)