What are the differential diagnoses and causes of a webbed neck in a 10-year-old female?

Webbed Neck in a 10-Year-Old Female: Differential Diagnosis and Causes

Turner syndrome is the most likely diagnosis in a 10-year-old female presenting with webbed neck, and should be the primary consideration until proven otherwise. 1

Primary Differential Diagnoses

Turner Syndrome (Most Common)

• Turner syndrome (45,X karyotype) is the classic cause of webbed neck in prepubertal females, characterized by congenital lymphedema that creates the characteristic pterygium colli deformity 1
• Associated features include:
  • Short stature (nearly universal finding) 1
  • Cardiovascular abnormalities: bicuspid aortic valve (30%), coarctation of the aorta, thoracic aortic aneurysm risk 1
  • Premature ovarian failure and delayed/absent puberty 1
  • Lymphedema of hands and feet (may be present at birth or in childhood) 1
  • Low posterior hairline extending onto the neck 2, 3, 4
  • Shield chest with widely spaced nipples 1

Noonan Syndrome (Second Most Common)

• Noonan syndrome presents with webbed neck but occurs in both males and females, caused by PTPN11 gene mutations (>50% of cases) or mutations in SOS1, RAF1, or KRAS genes 1
• Key distinguishing features from Turner syndrome:
  • Normal karyotype (46,XX in females) 1
  • Cardiac abnormalities: pulmonary valve stenosis (most common), hypertrophic cardiomyopathy 1
  • Hypertelorism (widely spaced eyes) 1
  • Low-set, posteriorly rotated ears 1
  • Bleeding diathesis: thrombocytopenia or abnormal platelet function 1
  • Developmental delay may be present 1

Klippel-Feil Syndrome (Less Common)

• Characterized by congenital fusion of cervical vertebrae causing short neck appearance and webbing 3, 4, 5
• Clinical triad (present in minority of patients):
  • Short webbed neck 3, 4, 5
  • Low posterior hairline 3, 4
  • Severely limited neck range of motion (key distinguishing feature) 3, 4, 5
• Associated anomalies include scoliosis, renal abnormalities, and hearing loss 3, 4, 5

Anatomical Basis of Webbed Neck

The webbed neck deformity results from subcutaneous fibrous bands and shortened trapezius muscles extending from the mastoid process to the acromion, creating bilateral skin folds 3, 4

• In Turner syndrome, this develops from persistent fetal lymphedema that fails to resolve 2, 3
• The web contains thickened fascia and connective tissue bands that restrict neck mobility 3, 4

Critical Diagnostic Workup

Initial Evaluation

• Obtain karyotype analysis as the definitive test to diagnose or exclude Turner syndrome 1
• Measure height and plot on growth curve - short stature strongly suggests Turner syndrome 1
• Cardiovascular evaluation:
  • Echocardiography to assess for bicuspid aortic valve, coarctation, and other structural abnormalities 1
  • Blood pressure in all four extremities (coarctation screening) 1
• Cervical spine radiographs if limited neck mobility suggests Klippel-Feil syndrome 3, 5

Genetic Testing Strategy

• If karyotype is normal (46,XX) but phenotype suggests genetic syndrome, proceed with targeted gene panel testing for Noonan syndrome (PTPN11, SOS1, RAF1, KRAS) 1
• Consider broader RASopathy panel if Noonan syndrome genes are negative 1

Important Clinical Pitfalls

Do not assume webbed neck is an isolated cosmetic finding - it is nearly always associated with significant systemic abnormalities requiring comprehensive evaluation 1

Turner syndrome patients require lifelong cardiovascular surveillance due to progressive aortic dilation risk and potential for aortic dissection, even with initially normal imaging 1

In Klippel-Feil syndrome, cervical spine instability poses anesthetic risks - always obtain imaging before any procedure requiring intubation 5

Management Implications

Turner Syndrome

• Initiate growth hormone therapy if growth velocity is impaired 1
• Estrogen replacement therapy at appropriate age for pubertal induction 1
• Annual cardiovascular imaging to monitor aortic dimensions 1
• Surgical correction of webbed neck is elective and typically performed after age 9-10 years using Z-plasty techniques 2, 4, 6

Noonan Syndrome

• Cardiac evaluation and management based on specific lesions identified 1
• Hematologic assessment before any surgical procedures due to bleeding risk 1
• Growth hormone therapy may be beneficial in some cases 1

Surgical Correction Considerations

• Modified Z-plasty with excision of fibrous bands and hair-bearing skin provides optimal cosmetic and functional results 4, 6
• Surgery addresses both the webbing and low posterior hairline 2, 4
• Best outcomes achieved when performed after age 9-10 years with complete excision of subcutaneous bands 2, 4, 6