LONG CASE RESOURCE

Approach to Short Stature

Achondroplasia • MRCP (UK) PACES

A structured PACES approach to a patient presenting with disproportionate short stature. Learn focused history, recognise the characteristic examination findings, identify neurological complications, explain the diagnosis and answer common examiner questions confidently.

10 min read Presenting Complaint High Yield

At a Glance

Presentation Disproportionate short stature with limb weakness
Likely Diagnosis Achondroplasia
Classic Signs Rhizomelic limb shortening, frontal bossing and mid-face hypoplasia
Major Complication Lumbar spinal stenosis with neurological deficit
Genetics FGFR3 mutation (Autosomal Dominant)
PACES Tip Always look for neurological complications before discussing the skeletal features

PACES Approach

① Confirm disproportionate short stature ② Screen for spinal stenosis & neurological symptoms ③ Examine head, spine and limbs ④ Confirm Achondroplasia & exclude differentials ⑤ Explain genetics, complications & long-term care

Overview

Achondroplasia is the commonest cause of disproportionate short stature and is an autosomal dominant skeletal dysplasia caused by mutations in the FGFR3 gene. In PACES, candidates should recognise the characteristic body proportions, identify neurological complications such as spinal stenosis, screen for associated problems including hearing loss, obstructive sleep apnoea and hydrocephalus, and explain the diagnosis sensitively to the patient. :contentReference[oaicite:1]{index=1}

Structured History

  • Onset and progression of lower limb weakness
  • Difficulty walking, climbing stairs or frequent falls
  • Numbness or altered sensation in the legs
  • Back pain or symptoms suggesting spinal stenosis
  • Bladder or bowel dysfunction (red flag)
  • Knee pain limiting mobility
  • Headache, vomiting or blurred vision (hydrocephalus)
  • Snoring, witnessed apnoeas or daytime somnolence
  • Recurrent ear infections or hearing impairment
  • Family history of short stature or Achondroplasia

Examination

  • Disproportionate short stature
  • Rhizomelic shortening of the upper limbs
  • Large head with frontal bossing
  • Mid-face hypoplasia with depressed nasal bridge
  • Normal trunk length
  • Thoracolumbar kyphosis or lumbar lordosis
  • Bowing of the tibiae
  • Clinical features of knee osteoarthritis
  • Assess hearing if appropriate
  • Complete lower limb neurological examination

Differential Diagnosis

Hypochondroplasia Pseudoachondroplasia Other skeletal dysplasias Familial short stature Growth hormone deficiency Turner syndrome Noonan syndrome Down syndrome

Investigations

  • Diagnosis is usually clinical
  • FGFR3 genetic testing
  • MRI spine for spinal stenosis
  • MRI craniocervical junction if neurological symptoms
  • CT brain if hydrocephalus suspected
  • Audiology assessment
  • Sleep study when obstructive sleep apnoea is suspected
  • Routine pre-operative investigations if surgery is planned

Diagnosis

Achondroplasia with suspected lumbar spinal stenosis

The diagnosis is suggested by disproportionate short stature, rhizomelic limb shortening, frontal bossing, mid-face hypoplasia and normal trunk length. Progressive lower limb weakness raises concern for spinal canal stenosis requiring urgent assessment.

Management

Immediate Priority Assess neurological deficit and exclude spinal cord compression
Multidisciplinary Care Genetics, Orthopaedics, Neurosurgery, Physiotherapy and Occupational Therapy
Long-term Care Monitor hearing, sleep apnoea, obesity, spinal complications and osteoarthritis

Explaining to the Patient

"From your history and examination, the most likely diagnosis is Achondroplasia, a genetic condition affecting bone growth. Your current leg weakness may indicate narrowing of the spinal canal, which needs urgent investigation. Although there is no cure for the underlying condition, treatment focuses on managing complications, maintaining mobility and improving quality of life."

Examiner's Corner

What are your clinical findings?
  • Disproportionate short stature
  • Rhizomelic shortening of the limbs
  • Large head with frontal bossing
  • Mid-face hypoplasia with depressed nasal bridge
  • Normal trunk length
  • Thoracolumbar deformity
  • Bowing of the tibiae
  • Lower limb neurological deficit suggesting spinal stenosis
What is your unifying diagnosis?

The patient has Achondroplasia, the commonest skeletal dysplasia causing disproportionate short stature. The progressive lower limb weakness is most likely due to lumbar spinal stenosis, a recognised neurological complication.

Common viva questions
  • What causes Achondroplasia?
  • What is the inheritance pattern?
  • Why does spinal stenosis occur?
  • What complications should be screened for?
  • How would you investigate this patient?
  • How would you counsel regarding pregnancy?
  • What advice would you give regarding future children?
Key investigations
  • Clinical diagnosis supported by examination
  • FGFR3 mutation testing
  • MRI spine for spinal stenosis
  • MRI craniocervical junction if neurological signs
  • CT brain if hydrocephalus suspected
  • Audiology assessment
  • Sleep study if obstructive sleep apnoea is suspected

Pathfinder Pearls

Normal trunk length is a key clue Rhizomelic limb shortening is classic Always inspect the face Look for frontal bossing Check for spinal stenosis Examine hearing Think hydrocephalus Remember obstructive sleep apnoea FGFR3 mutation Autosomal dominant inheritance

Common Pitfalls

  • Failing to perform a complete lower limb neurological examination.
  • Ignoring bladder or bowel symptoms suggesting spinal cord compression.
  • Missing hearing impairment or recurrent ear infections.
  • Not asking about symptoms of obstructive sleep apnoea.
  • Confusing Achondroplasia with proportionate short stature.
  • Forgetting pregnancy counselling and genetic advice.
  • Overlooking hydrocephalus in patients with headaches or visual symptoms.

Master MRCP (UK) PACES with PACES Pathfinders

Develop a structured approach to presenting complaints, communication stations and short cases through live interactive teaching, mock stations, examiner-focused discussion and recorded sessions.

View Current Course Join via WhatsApp