Median nail dystrophy (dystrophia unguium mediana canaliformis or Heller dystrophy) consists of a longitudinal split defect in the middle of the nail plate running from the cuticle to the free edge. Often, short cracks extend laterally in a proximal direction from the split creating a herring-bone or fir-tree appearance. It may be associated with an enlarged lunula. Symmetrical involvement of both thumbnails is most common, though involvement of other fingers and toes has been observed.
The origin of median nail dystrophy is unknown in most patients, though certain cases have been associated with oral isotretinoin therapy. Familial cases have been reported. In approximately 20% of patients, there is known antecedent trauma. Spontaneous regression may be observed, but recurrences are common.
ICD10CM: L60.3 – Nail dystrophy
SNOMEDCT: 86393005 – Median nail dystrophy
Differential Diagnosis & Pitfalls
Habit tic deformity is the main differential diagnosis. The classic habit tic deformity shows a central depression that may run to the free edge of the nail. The depth of the central depression is proportional to the intensity of the trauma and may form a true longitudinal split. Multiple transverse grooves of variable length are spread along the length of the nail plate. They have the appearance of "washboard nails" and may be filled with dirt. An enlarged lunula (macrolunula) is almost always seen. Swelling, redness, and scaling of the proximal nail fold may be associated. The presence of a swollen, red proximal nail fold and an acknowledged habit of manipulating the nails are the keys to distinguishing habit tic deformity from median nail dystrophy.
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.