Rare genetic disorder usually apparent at birth or
during infancy. Characterized by dysplasia of the fingernails and toenails,
aplasia or hypoplasia of the patellae, webbing of skin at the elbow(s), and
abnormal bilateral projections of the iliac superior crest. Other features
include glaucoma (open-angle glaucoma) and “cloverleaf-shaped iris”
(Lester iris). Approximately 30 to 40% of patients may also develop
nephropathy, which is usually apparent during childhood or later in life.
Onychodystrophy of the thumbs and dysplastic patellae in a patient with
Hereditary Osteo-Onycho-Dysplasia; HOOD Syndrome;
Turner-Kieser Syndrome; Fong Disease.
Estimated incidence internationally is 1:50,000 live
births. Both sexes are affected equally. No racial predilection. Individuals
of any age can be affected.
First reported clinically by Chatelain in 1820, whereas
its hereditary nature was defined by Little in 1897.
This genodermatosis is an autosomal dominant
trait with variable expressivity and a high degree of penetrance. The
nail-patella locus is linked to the COL5A1 gene at the 9q34.1 chromosome locus.
This suggests that the syndrome is a connective tissue disease because the
gene codes for a portion of the type V collagen molecule. In addition, the
nail-patella locus and the ABO blood group locus are linked. The gene
involved is located on the long arm of chromosome 9.
It has been proposed that mutations in the COL5A1
gene may be involved in the pathogenesis of the nail-patella syndrome.
Electron microscopy shows characteristic ultrastructural
changes in the glomerulus where many collagen fibrils are present in the
thickened basement membranes and in mesangial matrix of otherwise normal
glomeruli; this process is also known as collagenation of glomerular basement membrane. Radiologic examination of the
pelvis and elbows differentiates this disorder from other causes of
micronychia during childhood.
Nail deformities are recognized at birth and do
not progress: nails are hypoplastic, discolored, and have poorly formed
lunulae and/or splitting, most commonly of the thumbnail. Skeletal
involvement usually presents with knee dislocation, pain, or gait
disturbance. Hypoplasia of first ribs, malformed sternum, spina bifida,
dislocation of the head of radius, scoliosis are also seen. Both elbow and
knee dysplasia may lead to permanent restrictive deformities (incomplete
extension). Cloverleaf pigmentation of the inner margin of the iris in
50% of patients. Nephropathy is commonly presented as proteinuria (50%
of patients). The majority of patients with renal involvement have no
associated mortality; however, in approximately 20%, slow progression to
renal failure occurs within 5 to 25 years. Associated systemic abnormalities
include cleft lip and palate, mental retardation, sensorineural hearing
loss, hypoplasia or aplasia of some muscles (pectoralis minor, triceps,
quadriceps), cataract, and ptosis.
Evaluate airway for potential
difficulty with direct laryngoscopy and tracheal intubation in the presence of cleft lip/palate.
Assess the extent of renal involvement and any drug ...