Aarskog syndrome (faciogenital dysplasia)
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A short boy with hypertelorism, a widow's peak, and a small upturned nose has a "shawl scrotum": scrotal skin extending superiorly to surround the base of the penis. Hands are short with simian creases and lax interphalangeal joints showing a characteristic "swan-neck" configuration.
X-linked recessive (most common); FGD1 (encodes a guanine nucleotide exchange factor for CDC42) at Xp11. Some autosomal dominant families have been reported with variable molecular cause.
- Short stature: typically –2 to –4 SD
- Facial: hypertelorism, widow's peak, small upturned nose, broad/flat philtrum, anteverted nares, ear anomalies
- Genital (the discriminating feature): shawl scrotum in males (scrotum wraps around penis base); cryptorchidism common
- Limbs: brachydactyly, short broad hands, hyperextensible/lax joints with characteristic "swan-neck" finger flexion
- Mild-to-borderline cognitive impairment in some
- Clinical (shawl scrotum + facial gestalt + brachydactyly highly suggestive)
- FGD1 sequencing for X-linked form
- Noonan syndrome: hypertelorism + short stature + cardiac findings (different facies, no shawl scrotum)
- Robinow syndrome: fetal facies, mesomelic limb shortening, genital anomalies; AD or AR forms
- Pseudohypoparathyroidism (Albright osteodystrophy): brachydactyly + round face + obesity + hypocalcemia
- Endocrinology: monitor growth; growth hormone considered case-by-case
- Urology: cryptorchidism repair
- Ophthalmology: hypertelorism evaluation, refraction
- Developmental: school-based supports if needed
- Genetic counseling: X-linked → female carriers may have mild features; ~50% recurrence in sons of carriers
"Shawl scrotum" is the pathognomonic finding. If you see it on a clinical photo, Aarskog should be on your differential immediately.