BACKGROUND: Bathing suit ichthyosis (BSI) is an uncommon phenotype classified as 
a minor variant of autosomal recessive congenital ichthyosis (ARCI).
OBJECTIVES: We report a case of BSI in a 3-year-old Tunisian girl with a novel 
mutation of the transglutaminase 1 gene (TGM1).
CASE REPORT: This infant had been born with a collodion membrane encasing her 
entire body. From the age of three months, brownish scaling was noted on the 
bathing suit area. Histology showed orthohyperkeratosis with acanthosis of the 
epidermis. The granular layer was normal, and the superficial dermis was mildly 
inflammatory, confirming a diagnosis of proliferating ichthyosis. Molecular 
analysis in the patient and her parents revealed the mutation I304F of TGM1. 
Treatment with emollients and keratolytics partially improved the patient's skin 
condition.
CONCLUSIONS: Bathing suit ichthyosis is an uncommon phenotype unique in its 
topography, which involves the trunk but spares the face and extremities. 
Previous studies using molecular analysis have shown that BSI is caused mainly 
by mutations in TGM1. Twenty missense mutations have been reported in BSI. Of 
these 20 missense mutations, nine occurred only in patients with the BSI 
phenotype and 11 were common to BSI and other types of ARCI. Until recently, 
there has been no genotype-phenotype correlation. Therefore, the same mutation 
of the transglutaminase 1 could result in either generalized ARCI or BSI. The 
present case demonstrates this phenotype in a White Tunisian patient with a 
novel mutation of TGM1 (I304F) not previously reported in BSI.