Localized longitudinal erythronychia
When the red discoloration is limited to a single nail, the differential shifts, said Dr. Lipner. With a hematoma, there’s often a history of trauma, and dermoscopy will show characteristic globules and streaks.
The first clue that erythronychia caused by onychopapilloma can be seen at the lunula: There will often be a comet- or pencil-shaped point to the discoloration in that region. But, she said, “the key is to do dermoscopy at the free edge of the nail plate. In 100 percent of cases, there will be a subungual hyperkeratotic papule” that will solidify the diagnosis.
Histopathology of onychopapillomas – a relatively recently recognized entity – will show nail bed and distal matrix acanthosis, with the distal nail bed showing matrix metaplasia, Dr. Lipner said.
Glomus tumors arise from cells of the glomus body, a specialized vascular apparatus that is involved in temperature regulation. “These structures are abundant in the digits and the subungual region,” said Dr. Lipner, which means that glomus tumors – a benign lesion – may develop subungually. Glomus tumors can be idiopathic, but she added, “think neurofibromatosis type 1 if you see multiple glomus tumors.”
Glomus tumors will present with longitudinal erythronychia, with a distal split of the nail sometimes accompanying the discoloration. A round bluish to gray nodule can also be seen. A thorough history and exam can help solidify the diagnosis, said Dr. Lipner; there’s a characteristic triad of point tenderness with the application of pressure to the nail, pain, and cold hypersensitivity.
Classically, the point tenderness is assessed by Love’s test, which elicits severe pain when the subungual tumor is pressed with a small object like the end of paper clip or a ballpoint pen. Application of a tourniquet to the arm after elevation, termed Hildreth’s test, should alleviate subungual glomus tumor pain, and release of the tourniquet causes an abrupt and marked recurrence of pain. Immersing the patient’s affected hand in cold water also increases glomus tumor pain.
“Imaging can be quite helpful” to confirm a glomus tumor diagnosis, said Dr. Lipner. “X-ray is cheap, and you can see erosions in 50% of patients.” However, she added, doppler ultrasound and magnetic resonance imaging are more sensitive, detecting tumors as small as 2 mm.
“Biopsy with histopathology is the gold standard in making the diagnosis” of glomus tumor, though, she noted. Pathologic examination will show monomorphic cells with small caliber vascular channels.
Malignancy is actually uncommon with erythronychia, though it’s always in the differential diagnosis, she said.
In one case series examining subungual squamous cell carcinomas, common findings included onycholysis and localized hyperkeratosis, along with longitudinal erythronychia. “This may be subtle; splinter hemorrhages can also be present,” noted Dr. Lipner, adding, “If there are any symptoms, or an evolving band, a biopsy is indicated.”
“Even with erythronychia, the presentation can be quite variable,” she said. Nail unit melanoma can count erythronychia among the presenting signs. Clues that should raise suspicion for melanoma can include a wide band and prominent onycholysis, especially distal onycholysis and splintering. Again, she said, “biopsy with histopathology is the gold standard in making the diagnosis”; any symptoms or evidence of an evolving band should trigger a biopsy.
Dr. Lipner had no conflicts of interest relevant to her presentation.
SOURCE: Lipner S. Summer AAD 2019, Presentation F035.