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X-linked ichthyosis with seizures, ADHD, and autism spectrum disorder: a case report with an uncommon clinical presentation.

INTRODUCTION AND IMPORTANCE: X-linked ichthyosis (XLI) is a genetic condition characterized by scaly skin due to steroid sulfatase (STS) deficiency, often associated with additional neurodevelopmental issues. CASE PRESENTATION: A 10-year-old male child was admitted to the dermatology department. The child had been born prematurely at 26 weeks' gestation with a low birth weight of 1.6 kg. He presented with seizures characterized by abnormal upper-limb movements and was diagnosed with congenital ichthyosis. The child exhibited delayed language and motor development, learning difficulties, microcephaly, and dry, scaly skin, which he habitually peeled and ingested. Genetic analysis (single-nucleotide polymorphism and combined comparative genomic hybridization) revealed a 1.65 Mb deletion on chromosome Xp22.31 affecting the STS gene and other adjacent genes. The patient had low STS enzyme activity (3.5 nmol/hour/protein) in adipose tissue. Neuroimaging showed no structural abnormalities, though an electroencephalogram indicated mild slowing. CLINICAL DISCUSSION: Given the established association between STS deletions and neurodevelopmental as well as psychiatric comorbidities, early recognition of emerging psychiatric features is essential. Given the established association between STS deletions and neurodevelopmental as well as psychiatric comorbidities, early recognition of emerging psychiatric manifestations is essential. Management should follow evidence-based recommendations for first-episode or early psychotic symptoms, emphasizing careful assessment, individualized pharmacological treatment when indicated, and multidisciplinary psychosocial support. Such an approach may improve clinical stabilization while avoiding premature diagnostic labeling. CONCLUSION: This case highlights the importance of early genetic diagnosis and personalized treatment approaches, integrating dermatological, neurological, and psychiatric care to optimize outcomes in XLI.

X-linked ichthyosis

X-linked ichthyosis due to steroid-sulphatase deficiency.

An assay of cultured skin fibroblasts identified several individuals with 3 beta-hydroxysteroid-sulphate sulphatase deficiency. All patients with this inborn error of metabolism had clinically apparent ichthyosis and a family history of this skin disorder compatible with X-linked inheritance. It is concluded that steroid-sulphatase deficiency is the bio-chemical basis of at least some cases of X-linked ichthyosis.

Adult

Estimating sex ratio biases in X-linked disorders: is there an excess of males in families with X-linked ichthyosis?

We derive the conditional probabilities for estimating the sex ratio in families ascertained through affected males for the study of X-linked recessive diseases. These conditional probabilities correct for the fact that the probability that a family will be ascertained increases with the number of males in the family. Data from four published studies for X-linked ichthyosis vulgaris are analyzed, three having an excess of males and one having a highly statistically significant excess of males. It is not known if this difference in the two samples represents a biological difference between the two populations or an unrecognized ascertainment bias.

Female

X-linked ichthyosis: a metabolic disease.

Sex-linked ichthyosis, a rather common genodermatosis, has recently been linked with deficiency of the enzyme steroid sulfatase. Data supporting this association and suggesting that alterations in lipid metabolism may cause abnormal keratinization are herein reviewed.

Chemical Phenomena

Enzymatic basis of typical X-linked icthyosis.

Steroid sulphatase activity was determined in cultured fibroblasts from 25 individuals with X-linked ichthyosis from four countries. All those with X-linked disease had markedly reduced enzyme levels compared with controls and patients with other types of ichthyosis. X-linked ichthyosis seems to be the result of a common mutation affecting the expression of steroid-sulphatase activity.

Adult

Enzyme histochemistry of the small intestine in inherited ichthyosis.

Enzyme histochemistry of biopsies from the small intestine of 5 patients with different forms of inherited ichthyosis and of 2 normal volunteers was performed. Two of the patients had ichthyosis vulgaris, two had non-bullous congenital ichthyosiform erythroderma and one had X-linked ichthyosis. The following enzymatic activities were examined: G6P-D, 6PG-D, NADPH2-TR, ALD-A, L-D, C-A, IC-D, S-D, M-D, NADH2-TR, ATP-AI, ATP-A II, ATP-A III, ATP-A IV, R5P-A, DHO-D, alphaGP-D, betaHOB-D, MAO, GL-D alphaGP-A I, alphaGP-A II, betaGP-A II, N.EST-A. No significant variations in the different enzymatic activities were found for the ichthyosis vulgaris and non-bullous C.I.E. cases. More pronounced variations were found in X-linked ichthyosis, with a decrease in C-A, IC-D, R5P-A, betaHOB-D, GL-D, alphaGP-A II and N.EST-A activity. Succinic dehydrogenase activity has been reported in the literature to be reduced in ichthyosis vulgaris and bullous C.I.E. However, the results obtained for our patients showed equal or higher reaction levels than in the controls.

Histocytochemistry

Regional assignment of the steroid sulfatase-X-linked ichthyosis locus: implications for a noninactivated region on the short arm of human X chromosome.

The expression of steroid sulfatase (SS; sterol-sulfatase; sterol-sulfate sulfohydrolase, EC 3.1.6.2), a microsomal enzyme that catalyzes the hydrolysis of a variety of 3beta-hydroxysteroid sulfates, was evaluated in mouse-human hybrid clones. The mouse parental line, A9, was found to have little SS as determined by activity measurements. Human SS can be separated from mouse SS by electrophoresis. Two human fibroblast lines, one carrying an X/13 translocation [46,X,t(X;13)(p22;q12)] and the other carrying an X/20 translocation [46,X,t(X;20)(Xp20q;Xq20p)] were used as the human parental lines. Several independently derived hybrid clones from each of the two fusion experiments were analyzed for the expression of human SS by activity measurements and electrophoresis. Cytogenetic analyses were done on these hybrid clones at the same passage level. The results showed that the expression of human SS in these cell hybrids was concordant only with the presence of the distal half (p22-->pter) of the short arm of the human X chromosome, thus assigning the locus for SS to Xp22-->Xpter. Earlier studies have shown that the deficiency of SS is the basis for the dermatologic condition X-linked ichthyosis, the gene for which is known to be located approximately 10 centimorgans from the Xg blood group locus. The localization of SS on the X chromosome indicates that Xg locus may be on the short arm of X and possibly on its distal half. The Xg locus is thought to escape X-inactivation in man, and recent investigations suggest that the SS locus also escapes X-inactivation. Our results thus provide evidence for the location of an apparently noninactivated site on the distal half of the short arm of the human X-chromosome that contains the locus for SS and possibly the Xg locus.

Chromosome Mapping

Non-inactivation of an x-chromosome locus in man.

Cloned fibroblasts from women heterozygous for X-linked ichthyosis (steroid sulfatase deficiency) were examined to see whether or not this locus is subject to X-inactivation. Of 103 clones examined, all had normal levels of steroid sulfatase activity. Two of the women studied were also heterozygous for glucose-6-phosphate dehydrogenase deficiency. This allowed the demonstration that both X chromosomes were represented as the active X in various clones and that selection did not account for these findings. Thus, the steroid sulfatase locus, like the Xga locus to which it is linked, appears to escape X-inactivation in man.

Dehydroepiandrosterone

Ichthyosis vulgaris showing features of the autosomal dominant and X-linked recessive variants in the same family.

A family in which the mother and six of her sons present an ichthyosis of the vulgaris type has been analysed clinically, histologically and electron microscopically. Phenotypically the ichthyosis in the mother is purely of the dominant type, while that in all the affected sons shows, to varying degrees, features of both the dominant and X-linked recessive variants. The findings are interpreted as reasonably good evidence that the mother has transmitted to all her affected sons both the autosomal dominant and the X-linked recessive genes for ichthyosis. Although genetically this is a most unusual situation, it corresponds best to our findings.

Adolescent

X-linked dominant chondrodysplasia punctata. Review of literature and report of a case.

X-linked dominant chondrodysplasia punctata is a syndrome consisting of skeletal, ocular, and cutaneous anomalies with asymmetric involvement of the body. The skin lesions, the hallmark of this condition, are distributed in a linear or blotchy pattern and include congenital ichthyosiform erythroderma, systematized atrophoderma mainly involving the hair follicles, and circumscribed alopecia. The remaining scalp hair is in part normal and in part irregularly twisted and coarse. The eyebrows and lashes are sparse. The nails may be flattened and split into layers. Thirty-five cases of this new syndrome are reviewed, and an additional observation is reported. The ratio of females to males is 36:0. The concept of X-linked dominant chondrodysplasia punctata has been suggested, and it has been postulated that there is a connection between the mosaic phenotype and the limitation to the female sex. Both facts would be explained by an X-linked gene giving rise to a pattern of lyonization in females, and lethal in hemizygous males. The classification of chondrodysplasia punctata thus includes three forms: the rhizomelic type, the Conradi-Hünermann type, and the X-linked dominant type. Two of these, the rhizomelic type and the X-linked dominant type, are well-defined entities. Whether the Conradi-Hünermann type, after separation of the X-linked form, is still heterogeneous, remains to be determined.

Adolescent