How should I evaluate a 2½‑year‑old girl with height below the 3rd centile, weight 10 kg, otherwise healthy, whose mother is 155 cm and father is 167 cm?

Evaluation of a 2½-Year-Old Girl with Height Below 3rd Centile

Begin with serial growth measurements over 4–6 months to assess growth velocity, calculate mid-parental target height, and obtain basic laboratory screening—this child's height below the 3rd centile warrants systematic evaluation but the normal weight (10 kg ≈ 25th percentile for age) and otherwise well appearance suggest a non-pathologic variant is most likely. 1, 2

Calculate Mid-Parental Target Height First

• Mid-parental height = [(Mother's height + Father's height - 13 cm) ÷ 2] for girls 2, 3
• For this child: [(155 + 167 - 13) ÷ 2] = 154.5 cm (approximately 10th–25th percentile for adult women)
• This calculation reveals the parents themselves are relatively short, making familial short stature the leading differential diagnosis 2, 4

Assess Growth Velocity—The Single Most Critical Step

• Growth velocity distinguishes pathologic from non-pathologic short stature more reliably than any single height measurement 1, 2
• Obtain all prior growth measurements from birth to plot a complete growth trajectory 1, 3
• If the child has been tracking consistently along or parallel to the 3rd centile without crossing downward through multiple percentiles, this strongly suggests familial short stature or constitutional delay rather than pathology 1, 2
• Crossing multiple percentile lines downward after age 3 years is pathologic until proven otherwise and demands immediate comprehensive workup 1, 2
• Percentile crossing during the first 3 years of life is often physiologic (healthy infants establishing their genetic growth potential) and should not trigger alarm 1, 2, 3

Key Historical Red Flags to Elicit

• Birth weight and length, gestational age: IUGR/SGA is defined as birth measurements <10th percentile (or >2 SD below mean), and most healthy SGA infants achieve catch-up growth by age 2 years 2, 4
• Feeding history and symptoms of malabsorption: chronic diarrhea, abdominal distension, or poor appetite suggest celiac disease or other GI pathology 3
• Developmental milestones: delays may indicate syndromic causes 2
• Maternal alcohol exposure: can cause growth deficiency (though facial features would typically be present) 5

Physical Examination Priorities

• Measure sitting height and calculate sitting height/height ratio to determine if short stature is proportionate (most endocrine/nutritional causes) or disproportionate (skeletal dysplasias) 3
• Search systematically for dysmorphic features:
  • Turner syndrome stigmata in girls (webbed neck, shield chest, widely spaced nipples, cubitus valgus) 2
  • Facial features suggesting genetic syndromes 2, 3
• Head circumference plotted on growth chart: microcephaly may indicate syndromic or CNS pathology 3

Initial Laboratory Workup (If Growth Velocity Abnormal)

Order this panel if growth velocity falls below the 25th percentile for age/sex or if downward percentile crossing is documented: 2, 3

• Complete blood count (anemia, chronic disease) 2, 3
• Comprehensive metabolic panel (renal, hepatic, electrolyte abnormalities) 2, 3
• Thyroid function tests (TSH, free T4) to identify hypothyroidism 2, 3, 4
• Celiac disease antibodies (tissue transglutaminase IgA with total IgA) 3
• Bone age radiograph (left hand/wrist):
  • Bone age <chronological age suggests constitutional delay 2
  • Bone age ≈chronological age suggests pathologic cause 2
  • Bone age delayed >2 years warrants endocrinology referral 3
• IGF-1/IGFBP-3 if growth hormone deficiency suspected (particularly if growth velocity very low) 2, 4

When to Refer to Pediatric Endocrinology

Immediate referral is indicated for: 1, 3

• Crossing multiple percentile lines downward after age 3 years 1, 2
• Height >3 SD below mean (approximately <0.1st percentile) with no clear familial pattern 1, 4
• Growth velocity <4 cm/year (below 25th percentile) despite adequate nutrition 3, 6
• Bone age delayed >2 years from chronological age 3
• Associated dysmorphic features or disproportionate body habitus 1, 2

Most Likely Diagnosis in This Case

Given both parents are relatively short (mother 155 cm, father 167 cm), the child's weight is normal (10 kg ≈ 25th percentile), and she is otherwise well, familial short stature is the most probable diagnosis 2, 4

• In familial short stature, children demonstrate normal or near-normal growth velocity (4–7 cm/year) during childhood with consistent tracking along a lower percentile 1, 2
• These children have bone age approximately equal to chronological age 2
• Expected adult height will be consistent with mid-parental target height 2, 3

Monitoring Strategy

• Serial height measurements every 3–6 months are essential to confirm stable growth velocity and rule out emerging pathology 1, 3
• If growth velocity remains normal (≥25th percentile, approximately 5–6 cm/year at this age) and the child continues tracking parallel to her current percentile, reassurance and continued monitoring are appropriate 1, 6
• Re-evaluate immediately if growth velocity declines or percentile crossing occurs 1, 2

Critical Pitfall to Avoid

• A single height measurement below the 3rd percentile does NOT distinguish between benign familial short stature and serious pathology—growth velocity over time is far more informative 1, 2
• Among children with height >3 SD below mean, approximately 50% have non-pathologic variants (constitutional delay or familial short stature), but 23% have growth hormone deficiency, 13% have Turner syndrome, and 22% have primary growth failure 4
• Do not dismiss short stature in girls without considering Turner syndrome—karyotype is indicated if any stigmata are present or if growth velocity is abnormal 2, 4