Question 48:
A patient presents herself with stunted growth, web-like neck, and an absence of X chromosome. What would be your diagnosis of this genetic condition?
Turner syndrome is the diagnosis for a patient with stunted growth, web-like neck, and absence of an X chromosome (45,X karyotype), a classic chromosomal disorder in females.
Option Analysis
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(A) Down syndrome: Caused by trisomy 21 (extra chromosome 21); features include intellectual disability, flat facial profile, and heart defects—no X chromosome absence or web neck.
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(B) Turner syndrome: Correct answer. Results from complete/partial monosomy X (missing one X chromosome), leading to short stature, webbed neck (from lymphatic issues), ovarian dysgenesis, and other traits like low hairline.
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(C) Klinefelter syndrome: XXY karyotype in males; causes tall stature, gynecomastia, infertility—opposite growth pattern, no X absence or female presentation.
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(D) Cri-du-chat syndrome: 5p deletion; marked by cat-like cry, microcephaly, severe delays—no sex chromosome link, growth issues secondary, lacks web neck.
The genetic condition with stunted growth, web-like neck, and absence of X chromosome is Turner syndrome, affecting 1 in 2,500 females and crucial for GATE Life Sciences genetics prep.
Turner Syndrome Core Features
Turner syndrome arises from 45,X monosomy or mosaicism, causing short stature (average adult height 4’8″), pterygium colli (webbed neck from fetal lymphedema), and gonadal streak failure. Karyotyping confirms the missing X chromosome.
Genetic Cause and Variants
Complete X absence (monosomy X) or structural issues like isochromosome Xq disrupt SHOX gene, halting growth; 50% cases are mosaic (45,X/46,XX), milder phenotype. No inheritance—sporadic nondisjunction.
Associated Health Risks
Beyond physical traits: coarctation of aorta (30%), horseshoe kidney, hearing loss, thyroiditis, osteoporosis; hormone therapy (GH early, estrogen puberty) manages growth and puberty.
GATE Exam Relevance
Questions test symptom-karyotype links: web neck + short stature = Turner (not Klinefelter’s tallness); differentiate from Down (trisomy 21).
| Syndrome | Karyotype | Key Traits | Growth Pattern |
|---|---|---|---|
| Turner | 45,X | Web neck, short stature | Stunted |
| Down | 47,XX/XY+21 | Flat face, hypotonia | Normal/poor |
| Klinefelter | 47,XXY | Tall, hypogonadism | Tall |
| Cri-du-chat | 46,del(5p) | Cat cry, microcephaly | Poor feeding |
