What are the clinical findings and diagnostic methods for Rickets, including signs like the 'rosary' sign and how to assess them?

Clinical Findings and Assessment of Rickets

Key Skeletal Deformities and How to Identify Them

The rachitic rosary is identified by palpating prominent knobs of bone at the costochondral junctions along the rib cage, creating a beaded appearance under the skin that resembles a string of rosary beads. 1

Chest Wall Findings

• Rachitic rosary: Run your fingers along the anterior chest wall at the costochondral junctions bilaterally—you will feel enlarged, bead-like prominences where the ribs meet the cartilage 2, 1, 3
• Harrison's groove: Look for a horizontal indentation along the lower border of the thorax at the diaphragm insertion, where the softened ribs are pulled inward by diaphragmatic contraction 2, 1
• These findings are best appreciated by visual inspection from the side and direct palpation of the chest wall 2

Extremity Deformities

• Widened wrists and ankles: Palpate the distal radius/ulna and distal tibia/fibula for metaphyseal widening and thickening—these areas will feel enlarged and bulbous compared to normal 2, 4
• Lower limb deformities: Observe the child standing and walking to assess for varus (bow-legged) or valgus (knock-kneed) deformities, often with rotational components causing intoeing or extoeing 2
• Waddling gait: Watch the child walk—rickets causes a characteristic side-to-side waddling pattern due to muscle weakness and bone deformity 2, 4

Skull Abnormalities (Infants)

• Craniotabes: Gently press on the parietal and occipital bones—softened areas will feel like pressing on a ping-pong ball 4
• Frontal bossing: Observe the forehead for prominent bulging of the frontal bones 2, 4
• Delayed fontanelle closure: Palpate the anterior fontanelle—it remains abnormally large and open beyond expected age 4
• Dolichocephaly: Assess head shape for elongation with parietal flattening 2

Radiographic Assessment

Radiography of the knees, wrists, or ankles is sufficient to diagnose rickets—look for cupped and flared metaphyses with widened, irregular growth plates. 2

Key X-ray Findings

• Metaphyseal changes: The ends of long bones show cupping, fraying, and flaring at sites of rapid growth (distal femur, distal tibia, distal radius) 2, 4
• Widened growth plates: The physis appears abnormally wide and irregular rather than the normal thin, sharp line 2, 4
• Costochondral junction changes: Chest X-rays show the rachitic rosary as enlarged, irregular costochondral junctions 2
• Bone density: In X-linked hypophosphatemia specifically, cortical bone often appears thickened (unlike nutritional rickets where generalized osteopenia is common) 2

Physical Examination Sequence

Systematic Approach

• Growth assessment: Measure height and compare to previous measurements—look for decreased growth velocity and disproportionate short stature with relatively preserved trunk length 2, 4
• Muscle strength testing: Assess proximal muscle strength—weakness causes difficulty rising from sitting position and the waddling gait 2, 4
• Bone pain assessment: Palpate long bones for tenderness, particularly at metaphyseal regions 2, 4
• Dental examination: Look for dental abscesses (highly prevalent in children >3 years with X-linked hypophosphatemia) and poor dental condition 2

Laboratory Confirmation

Elevated alkaline phosphatase combined with abnormal calcium/phosphate metabolism confirms the diagnosis when clinical and radiographic findings are present. 2, 4

Essential Laboratory Tests

• Serum phosphate: Low in hypophosphatemic rickets; may be normal in early infancy (first 3-4 months) even when disease is present 2
• Alkaline phosphatase: Elevated in active rickets 2, 4
• Calcium: Usually low-normal range in hypophosphatemic rickets 2
• 25-hydroxyvitamin D: Low in nutritional rickets; normal or elevated in phosphopenic rickets 2, 5
• TmP/GFR calculation: Calculate tubular maximum reabsorption of phosphate per GFR to assess renal phosphate wasting 2

Critical Timing Considerations

• Age of presentation: Rachitic skeletal deformities typically become apparent around 6 months of age, with progression during the second year of life when walking begins 2
• Infantile rickets caveat: In young infants, skeletal abnormalities are subtle and often only detectable radiologically, making clinical diagnosis challenging 5
• Radiographic screening: Studies screening healthy children have found much higher prevalence than clinically diagnosed cases, indicating substantial underdiagnosis 5