Achondroplasia

🧬 Mutations in the fibroblast growth factor receptor-3 (FGFR3) gene on chromosome 4 cause achondroplasia. 🌟 Prognosis is generally good, and most individuals lead healthy lives, though they may face challenges such as spinal and respiratory issues. 📈 Life expectancy is usually normal with careful monitoring of complications.

📖 About

• 🦴 A non-lethal form of chondrodysplasia.
• 🧩 Disorder of cartilage leading to reduced bone growth.

🧬 Aetiology

• Genetic Mutation: 🔬 Caused by FGFR3 mutation on chromosome 4, producing an abnormal protein that inhibits long bone growth.
• Inheritance Pattern: 👨‍👩‍👧 Autosomal dominant. 💡 80% of cases are new mutations; if one parent is affected, there’s a 50% transmission risk.
• Pathophysiology: ⚖️ FGFR3 normally regulates cartilage → bone conversion. Overactivation blocks this, causing short limbs & skeletal changes.

🩺 Clinical Features

• 📏 Short Stature: Adult height ~122 cm (4 ft).
• 🦵 Disproportionately Short Limbs: Proximal shortening (rhizomelic pattern – short upper arms/thighs).
• 🧠 Macrocephaly: Large head, frontal bossing, depressed nasal bridge.
• 🌀 Spinal Issues: Kyphosis, lordosis, spinal stenosis → pain & neuro deficits.
• 💤 Hypotonia: Low muscle tone in infancy → delayed motor milestones.
• 😁 Dental Problems: Crowding, delayed eruption.
• 👂 Ear Infections: Recurrent otitis media due to narrow Eustachian tubes.

🛠️ Management

• 📊 Monitoring Growth & Development: Regular follow-up with paediatrician, orthopaedics, and neurology.
• 🔪 Surgical Interventions: For spinal stenosis, deformities, or selected limb lengthening procedures.
• 🏃 Physiotherapy: Improves strength, posture, and motor skills in hypotonia.
• 👂 Hearing & 🗣️ Speech Therapy: For recurrent ear disease or communication delays.
• 📚 Educational Support: Adjust learning environments for physical needs.
• 🧬 Genetic Counselling: Discuss inheritance, recurrence risk, and reproductive planning.

Cases — Achondroplasia

• Case 1 — Classic neonatal presentation 👶: A term newborn boy is noted to have a large head, frontal bossing, midface hypoplasia, and rhizomelic shortening of the arms and legs. Parents are of average stature. Radiographs: shortened long bones with metaphyseal flaring. Diagnosis: sporadic achondroplasia (FGFR3 mutation). Managed with genetic counselling and supportive monitoring.
• Case 2 — Developmental complications 🧠: A 2-year-old girl with known achondroplasia presents with delayed motor milestones, snoring, and recurrent otitis media. Exam: macrocephaly, short limbs, lumbar lordosis. MRI: narrowed foramen magnum causing cervicomedullary compression. Diagnosis: achondroplasia with neurological and ENT complications. Managed with neurosurgical referral, ENT support, and sleep apnoea assessment.
• Case 3 — Adult with orthopaedic issues 🦴: A 25-year-old man with achondroplasia presents with chronic back pain, limb numbness, and claudication. Exam: short stature (height 125 cm), exaggerated lumbar lordosis, limited hip extension. MRI spine: lumbar spinal stenosis. Diagnosis: achondroplasia with spinal stenosis. Managed with physiotherapy, analgesia, and neurosurgical decompression if severe.

Teaching Point 🩺: Achondroplasia is the most common skeletal dysplasia, caused by an activating FGFR3 mutation (autosomal dominant, but often sporadic). Key features: short stature with rhizomelic limb shortening, macrocephaly, frontal bossing, midface hypoplasia. Complications: otitis media, sleep apnoea, foramen magnum compression, spinal stenosis. Management is supportive, multidisciplinary (orthopaedics, neurosurgery, ENT, genetics).