A child born to consanguineous parents has large yellowish-brown scales over the entire body since birth. Biopsy shows hyperkeratosis with a normal granular layer. Enzyme assay shows deficiency of steroid sulfatase. The expected inheritance pattern and associated features are:

• A Autosomal recessive; normal at birth, presents in infancy
• B Autosomal dominant; generalized erythroderma and collodion baby
• C X-linked recessive; associated with corneal opacities and cryptorchidism ✓
• D Mitochondrial inheritance; associated with sensorineural deafness

Explanation

Steroid sulfatase deficiency causes X-linked recessive ichthyosis (XLI), affecting males. Steroid sulfatase (STS) on chromosome Xp22.3 is deficient, leading to accumulation of cholesterol sulfate in the stratum corneum, impairing desquamation. Clinical features include large, dark, adherent (dirty-brown) scales mainly on the trunk and extremities with relative facial and flexural sparing; normal granular layer on biopsy distinguishes it from lamellar ichthyosis. Associated features: corneal opacities (Descemet's membrane), cryptorchidism, and testicular cancer risk. Female carriers may have prolonged labor (fetal steroid sulfatase needed for cervical ripening). XLI spares the palms and soles, unlike autosomal recessive lamellar ichthyosis.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.