Bathing suit ichthyosis (BSI) is a rare form of ichthyosis in the group of autosomal recessive congenital ichthyoses (ARCI), together with lamellar ichthyosis (LI), congenital ichthyosiform erythroderma (CIE), harlequin ichthyosis, and self-healing collodion baby (SHCB). These in turn form part of the nonsyndromic ichthyoses,1,2 and their estimated prevalence in Spain is of 7.2 cases per million population, with a total of 144 cases reported. Among these, only 2 cases of BSI have been documented, 1.4% of all cases of ARCI.3 BSI was first described as a distinct disease in 20054 and it is characterized by presentation at birth as collodion baby; the characteristic distribution typically develops within a few months, with the appearance of thick brownish scales on the trunk, with sparing of the limbs and face, giving the appearance of a woman's bathing suit.2,5 This condition is due to mutations in the TGM-1 gene,1,2,5–8 which provoke a phenotype similar to LI but milder; the distribution depends on body temperature, as the function of the enzyme transglutaminase-1 is only altered in the warmest areas of the body, typically the central regions.8

We presented the case of a 6-year-old girl of Spanish origin, with no family history of interest and no known consanguinity, product of a well-controlled second gestation. At birth the condition presented as collodion baby. This resolved without complications, but when the infant was 6 months old, thick brownish scales started to develop in a specific distribution, only affecting the inguinal and axillary regions (Figs. 1 and 2) and the central area of the trunk, with sparing of the face, limbs, hands, and feet. Diffuse desquamation and erythema of the scalp were also observed. Notably, there was no involvement of the nails or hair, no alteration of sweating, and no other signs of systemic involvement, nor was any deficit detected in the child's psychomotor development. On suspicion of BSI, we decided to perform genetic analysis, which confirmed the suspected diagnosis after finding 2 known pathogenic mutations in heterozygosis, in both alleles of the TGM-1 gene: c.424C>T; p.Arg142Cys described in BSI8 and c.919C>G; p.Arg307Gly described in LI.9

Figure 1.

Body distribution of the lamellar scales outlining the form of a woman's bathing suit, with sparing of the limbs and of the central area of the abdomen.

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Figure 2.

Thick dark scales down the midline of the back.

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The patient's clinical course has at all times been characteristic of the disease (chronic and recurrent), and the manifestations have been managed using moisturizers and the application of preparations of 10% N-acetyl-cysteine plus 5% urea10 (Fig. 3). However, the bad smell of the N-acetyl-cysteine preparation has occasionally interfered with adherence to treatment.

Figure 3.

Good control of the disease with the preparation of 10% N-acetyl-cysteine plus 5% urea in a moisturizing body milk.

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After 3 years of good control, the mother consulted for a new pregnancy and the possibility of giving birth to another child affected by BSI. There are now 7 genes known to be implicated in different types of ARCI. Of these, the gene most frequently implicated is, without doubt, TGM-1.6,7 However, this is the only gene known to be implicated in BSI.6 Twenty different mutations of this gene have been detected, 9 of which are exclusive to BSI, whereas the other 11 are mutations shared with other types of ARCI.5 Thus 2 individuals with the same mutations can present different phenotypes.5,6 In fact, families have been described in which siblings with the same genetic changes have presented different types of ARCI.5 There are also isolated reports of cases in which the phenotype has changed with the age of the child, passing from BSI to generalized forms of LI/CIE or even to self-healing collodion baby.5,6 It would appear likely that environmental factors may influence the phenotypic expression of these genetically identical conditions. In our case, one of the mutations found had already been reported in LI.9 Given the possibility described in the literature of LI in siblings of patients with BSI with the same mutations,5,6 we agreed with the mother to perform prenatal screening: mutations of the TGM-1 gene in the fetus were excluded. The gestation was uneventful and the infant was healthy.

In conclusion, BSI is a rare genodermatosis belonging to the group of ARCI. It has a series of clinical and diagnostic peculiarities that we should be aware of. Although the diagnosis is usually clinical, confirmation can only be made by genetic analysis of the TGM-1 gene. This is the only gene implicated in this condition, but its mutations are also the most prevalent in other forms of ARCI, and many of the mutations are common to the different forms; thus, individuals with the same genetic load can develop different phenotypes, and these can even be dynamic, with changes occurring during life. All these features are important with respect to the prognosis in our patients and to correct genetic counselling.