A 35 year-old Caucasian female presented to clinic for a
skin cancer screening examination. She had chronic
gastrointestinal problems including reflux, bloating,
constipation, and diarrhea. She had also experienced right
arm numbness, especially with flexion, in addition to abnormal
sensations in her feet and had difficulty standing in
one position for long periods of time. Cold weather caused
pain and color changes in her fingers. Additionally, she was
on chronic vitamin D supplementation with a history of nontraumatic
bone fracture. Calcium supplements were avoided
given her gastrointestinal symptoms.
Her hypertension had been treated with an ACE inhibitor. She
was a smoker and also has hyperlipidemia. Of note, she and
her father have glaucoma and her paternal grandmother developed
blindness at a young age however she does not know
much additional family history.
On physical examination, she is unable to supinate her forearms
and has a swan-neck appearance of multiple digits. Firm
protrusions can be palpated along her bilateral lateral lower
back. She has nail dysplasia involving her thumbnails and 2nd digits in addition to triangular lunulae involving most fingernails.
Interestingly, her daughter has similar physical findings.
Nail patella syndrome (NPS) (also known as hereditary osteo-onychodysplasia, Turner-Keiser syndrome, Fong disease,
and nail-patella-elbow syndrome) is an inherited, autosomal
dominant disorder that affects the limbs, eyes, kidneys, and
nails.2,4 It is relatively rare with a prevalence of 1:50,000.2 The syndrome was first described in the 19th century and is
due to a mutation in LMX1B, a transcription factor important
for regulating the development of nail, bone, and glomerular
basement membrane.6,4 This gene is also necessary for the
normal functioning of renal glomerular podocytes as it maintains
their actin cytoskeleton.1
This condition is not life threatening however it may cause
functional impairments and morbidity related to bone abnormalities,
impaired renal function, and glaucoma. The dermatologic
findings include various nail dystrophies and have aesthetic implications.
Nail involvement occurs in 98% of patients, is typically
symmetrical and often more severe from 2nd to 5th fingernails.
These patients may have triangular lunulae, severe nail dysplasia,
and micronychia in addition to absence of the medial and
distal aspects of the thumb and 2nd digit fingernails.4
Iliac horns are pathognomonic for nail-patella syndrome and
contain cortex and medulla continuous with the iliac bone.
The gluteus medius muscle insertion site marks their location
and from this point they protrude posterolaterally. They
are frequently palpated during physical examination however
should have no impact on the patients' gait.3 The patellae
may be hypoplastic or completely absent and patients may
complain of knee pain. Dysplasia of the radial heads is also
seen and may lead to the inability of forearm supination.4 Not specific to NPS, swan neck deformities of the fingers
may be present and are due to hyperextension at proximal
interphalangeal joints in addition to flexion at distal interphalangeal
joints.2 Although patients with NPS may not have an
increased risk of osteopenia or osteoporosis, they have been
found to have decreased bone mineral density and increased
prevalence of fractures, particularly involving long bones of
Renal involvement is present in up to 60% of patients with NPS.
Like our patient, many develop hypertension. Although most