NAIL-PATELLA SYNDROME
DEFINITION:
A multisystem disorder characterized by dystrophic nails,
hypoplastic or absent patellae, and renal disease.
EPIDEMIOLOGY:
- incidence: 2.2/100,000
- age of onset:
- risk factors:
- familial - autosomal dominant
PATHOGENESIS:
- disorder results in a secondary glomerulopathy
- unknown etiology but may be a disorder of collagen with an
abnormality in the synthesis, assembly, or degradation of
collagen
CLINICAL FEATURES:
- microscopic hematuria
- proteinuria (minimal -> nephrotic)
- edema, hypertension
2. Minor
- renal stones
- congenital malformations - vesicoureteral reflux, atrophy,
hypoplasia, duplications
3. Complications
- Nephritic Syndrome (edema, hypertension, azotemia,
oliguria)
- Nephrotic Syndrome (edema, hypoalbuminemia, hyperlipidemia)
- Chronic Renal Failure (CRF)
2. Musculoskeletal Manifestations
- dystrophic finger and toenails
- absent, discoloured, koilonychia, longitudinal ridges,
triangular lunulae
- changes are symmetric
- fingernails > toenails, thumbs > fingers
2. Patella (60%)
- absent or hypoplastic
- "knock-knee" deformity - lateral displacement on knee
flexion
- associated with osteoarthritis, osteoarthrosis, knee
effusions
3. Elbows
- aplasia, hypoplasia, posterior processes at distal ends of
humerus -> increased carrying angle with limited extension and
suppination
INVESTIGATIONS:
- hematuria, proteinuria
- microscope - glomerular pattern - damaged RBC's & RBC casts
2. Renal Biopsy
- LM - variable from normal to basement membrane thickening to
complete or segmental glonerulosclerosis
- EM - "moth-eaten" appearance is pathognomonic
- IFM - normal
3. Imaging Studies
- "Iliac Horns"
- in 80% and pathognomonic
- flared iliac crests with prominent ASIS
- hypoplastic or absent patella
- abnormal radioulnar articulation
- hypoplastic radial heads
MANAGEMENT:
- no treatment for underlying disorder
- multidisciplinary approach
- Paediatrics, Nephrology, Orthopedics, Rheumatology
2. Medical
- medical management of complications:
- fluid restriction, control hypertension, manage
hyperkalemia, manage pulmonary edema
2. Nephrotic Syndrome
- fluid restriction, salt-free diet, diuretics, albumin
transfusions, prednisone, alkylating agents
- see file on "Idiopathic Nephrotic Syndrome"
3. Chronic Renal Failure
- dialysis and transplantation for end-stage renal failure
(ESRF)
3. Prognosis
- usually benign although 10% develop ESRF
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