A 6-year-old boy presented with recurrent pyogenic abscess, runny nose, oral thrush & rash on perineal areas. Pus culture showed growth of Staphylococcus aureus. A test was performed whose finding is shown below. What is most common mode of inheritance of this disorder?
**Core Concept**
The boy's symptoms and the growth of Staphylococcus aureus suggest a chronic mucocutaneous disorder. The test finding is likely related to a genetic defect affecting the skin and mucous membranes. The disorder is characterized by impaired skin barrier function, leading to recurrent infections.
**Why the Correct Answer is Right**
The most common mode of inheritance of this disorder is X-linked recessive. This is due to mutations in the gene encoding for the protein filaggrin, which is crucial for skin barrier function. The disorder is characterized by impaired skin barrier function, leading to recurrent skin infections, atopic dermatitis, and asthma. The X-linked recessive pattern of inheritance is explained by the fact that the filaggrin gene is located on the X chromosome, and males (who have one X and one Y chromosome) are more frequently affected than females (who have two X chromosomes). Females can be carriers of the disorder, but they are less likely to exhibit symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** Autosomal dominant inheritance is incorrect because the disorder is more common in males and exhibits X-linked recessive inheritance.
**Option B:** Autosomal recessive inheritance is incorrect because the disorder is more common in males and exhibits X-linked recessive inheritance.
**Option C:** Mitochondrial inheritance is incorrect because the disorder is not associated with mitochondrial DNA mutations.
**Clinical Pearl / High-Yield Fact**
The filaggrin gene is a classic example of a gene associated with skin barrier function. Mutations in this gene can lead to a range of disorders, including atopic dermatitis, asthma, and recurrent skin infections.
**Correct Answer:** C. Mitochondrial inheritance is incorrect because the disorder is not associated with mitochondrial DNA mutations