What is the most likely etiology of mild curvature of the spine in a later teen female with asthma treated with inhaled corticosteroids (ICS)?

Adolescent Idiopathic Scoliosis (AIS) is the Most Likely Etiology

The mild spinal curvature in this late teen female is most likely adolescent idiopathic scoliosis (AIS), not a complication of inhaled corticosteroid therapy. AIS is the peripubertal development of spinal curvature of at least 10 degrees and represents the majority of scoliosis cases encountered in general practice 1, 2. The inhaled corticosteroids used for her asthma are not the cause of her scoliosis.

Why Idiopathic Scoliosis is the Answer

• AIS is extremely common in adolescent females, with the majority of scoliosis cases in this age group being idiopathic 1
• The timing fits perfectly: AIS develops during the peripubertal period, which aligns with "later teen" presentation 2
• Female predominance: AIS has a strong female predilection, making this diagnosis even more likely in a female patient 1

Why Inhaled Corticosteroids Are NOT the Cause

Inhaled corticosteroids at recommended doses do not cause skeletal deformities or scoliosis. The evidence is clear on this point:

• Low-to-medium dose ICS show no clinically significant effects on bone structure in children at guideline-recommended doses 3
• The CAMP study provides strong evidence that 4-6 years of ICS treatment at recommended doses does not affect bone mineral density in children 3
• Growth velocity effects are transient: While one-year studies show decreased growth velocity with ICS, long-term studies with budesonide and beclomethasone demonstrate no effect on final adult height 4
• ICS effects are fundamentally different from oral corticosteroids and do not cause the clinically important skeletal adverse effects seen with systemic steroids 3

Clinical Approach to This Patient

Evaluate for typical AIS characteristics:

• Confirm the diagnosis with standing posteroanterior and lateral spine radiographs to measure Cobb angle 1
• Rule out atypical features that would suggest secondary causes: back pain, neurological abnormalities, or congenital anomalies 1
• Assess skeletal maturity using Risser sign or bone age to determine risk of progression 1

Referral criteria:

• Refer to orthopedic specialist if curve is greater than 20 degrees in a patient 10 years or older 1
• Earlier referral indicated if atypical features present or associated with pain/neurological findings 1

Important Caveats

Do not discontinue or reduce inhaled corticosteroids based on concern about skeletal effects:

• The benefits of ICS therapy clearly outweigh any minimal risks when taken at recommended doses 4
• Uncontrolled asthma poses far greater risks to morbidity and quality of life than properly dosed ICS 5
• ICS should be titrated to the lowest effective dose to maintain asthma control, but this is standard practice regardless of scoliosis 5, 3

Consider congenital causes only if indicated:

• If scoliosis is diagnosed as congenital rather than idiopathic, evaluate for cardiac and renal abnormalities 1
• Mechanical "foundation" issues like spondylolisthesis can cause lumbar scoliosis but would have different clinical presentation 6