CHICAGO – When a child or adolescent comes to the dermatologist’s office with a concern about fingernails or toenails, physician antennae may go up. “The world is different in the world of pediatrics – and even in the world of adolescents,” said Sheila Fallon Friedlander, MD.
Dr. Sheila F. Friedlander
In adults, the most common cause of nail dystrophy is tinea, but for younger pediatric patients, less than 1% of nail problems are attributable to fungus, so dermatologists may need to look further.
“It’s so important in kids to do a good history and physical exam,” said Dr. Friedlander, professor of dermatology and pediatrics at the University of California, San Diego. History-taking should include determining whether the condition has been present since birth and how nail appearance has changed over time.
For Dr. Friedlander, the approach to nail abnormalities includes a full head and skin exam. “I always look at the teeth, the hair, the skin,” she said; underlying bony anomalies also may surface. A complete exam often will turn up important clues if a syndrome underpins the nail abnormalities, she said, speaking at the American Academy of Dermatology summer meeting.
Her exemplar patient, she said, is a 19-year-old male who comes in with a parent because he’s bothered by his fingernails, which are dystrophic and small. A head-to-toe exam shows micronychia of both toes and fingers, with lunulae that are triangularly shaped. The hair, skin, and teeth of the patient all were normal in appearance. However, “The knees and elbows were odd,” Dr. Friedlander said.
This patient has nail-patella syndrome. “Even though it’s rare, I want you to think about it,” Dr. Friedlander said. The autosomal dominant condition is seen in about 1 in 50,000 patients. It’s thought to be caused by heterozygous loss-of-function mutations in gene LMX1B, she said, that codes for a LIM homeobox transcription factor 1 beta.
Though the small nails and triangular lunulae may be what brings the patient to the dermatologist’s office, a careful exam and one radiograph can pick up a tetrad of anomalies, Dr. Friedlander said. Abnormalities can be seen in both the knees and elbows; the patellae are often small, and may even be absent. In addition, a hip radiograph will show characteristic “horns” on the posterior iliac crests.
Coming back to the dermatologic exam, Dr. Friedlander said nails may be absent, hypoplastic, and dystrophic – but those are features that can be shared with other nail disorders, inherited and acquired. The pathognomonic finding for nail-patella syndrome is the presence of the triangular lunula, she said.
Now that the diagnosis has been made, Dr. Friedlander asked about this young man: “Where will you refer him?” Knowing the diagnosis means that there are a lot of calls for your staff to make, she said.
The patient with knee patella syndrome should be referred to an orthopedist to assess knees and elbows; radial head subluxation also is common in these patients, she said.
An ophthalmologic referral is important as well; hyperpigmentation of the pupillary margin – a “Lester iris” – can be seen, and increased rates of cataracts and glaucoma also are associated with nail-patella syndrome.
“,” Dr. Friedlander said. Up to half of nail-patella syndrome patients will have kidney involvement that initially presents with hematuria and proteinuria. Because the LMX1B mutation impairs how podocytes and glomerular filtration slits develop and function, up to 10% can develop end-stage renal failure, she said.
Parents also should be on the lookout for associated behavioral issues: “The other thing that’s interesting is that these kids have an increased risk of [attention-deficit/hyperactivity disorder] and major depression,” Dr. Friedlander said.
Dr. Friedlander reported that she had no relevant conflicts of interest.
SOURCE: Friedlander, S. Summer AAD 2018. Session F004.