Alpha-thalassemia X-linked intellectual disability (ATRX) syndrome is a rare disorder characterized by facial dysmorphism, genitourinary tract abnormalities, alpha-thalassemia, and cognitive impairment. Patients present in early infancy with hypotonia, microcephaly, failure to thrive, and delayed milestones. We report a boy with strong family history of the Smith–Lemli–Opitz's syndrome (SLOS) phenotype. All affected family members displayed facial features and presentation identical to those of our patient. None had hypocholesterolemia. All affected family members were boys and have died. Molecular genetic testing in our patient revealed a likely pathogenic mutation in the X-linked recessive ATRX gene. We conclude that SLOS and ATRX syndrome are uncommon disorders sharing similar manifestations. Awareness of such similarity should prompt physicians to explore the possibility of ATRX syndrome in relatives of patients with unproven SLOS.

Smith–Lemli–Opitz's syndrome and ATRX syndrome are rare disorders that can share phenotypic similarity.

B.J. wrote the initial draft, clinical history, and participated in writing and critical review. K.S. participated in writing, editing, literature review, and critical review. P.M. conceptualized the case report, participated in writing, editing, literature review, and critical review. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

Received: 17 June 2023

Accepted: 09 December 2023

Article published online:
16 January 2024

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