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Median Nail Dystrophy refers to a longitudinal splitting down the middle of the nail. The nail also has smaller sized horizontal lines or cracks along this central split, which gives it the appearance of a fuzzy fir tree. The nail disorder is extremely rare and usually affects the thumbnails. The splitting begins from the cuticle at the base of the nail and continues to grow outwards till the edge.
In medical terminology it is also known as medial canaliform nail dystrophy or median canaliform dystrophy of Heller, named after Heller, who recorded the first known case of the disorder in 1928. Other names for the disorder are solenonychina, dystrophia unguis mediana canaliformis and nevus striatus unguis. Its exact etiology is as yet unresolved.
It is a condition affecting the nail plate of the thumbs, though on rare occasions it may be found in toenails or other finger nails. There is a symmetrical defect running down the nail plate that leads to longitudinal splitting of the nail. The splitting begins at the base of the thumb near the cuticle and proceeds down the middle of the nail towards the fingertip. Along with the longitudinal split there are a number of horizontal furrows in the nail. These lateral splits are responsible for the characteristic inverted fir tree appearance on the nail. The lunula is often enlarged as a result of pressure from the base of the nail.
A temporary defect of the nail matrix is the general cause for this disorder. It can be caused due to a sudden, harsh trauma to the nail or even by recurrent self-inflicted trauma. Pushing back the cuticle during a manicure may damage the nail plate, causing median nail dystrophy. Plucking a guitar with the thumbnail or even using mobile phones excessively can cause the problem. Biting the nail or plucking at the proximal skin may also be reasons for the longitudinal split to show up.
Median nail dystrophy may also develop as a reaction to specific drugs. Recorded cases include the disorder occurring when isotretinoin was used to treat acne, or alitretinoin was prescribed for chronic eczema. Other medicines that are retinoic acid based may also cause similar damage to the nails.
There is no gender predilection for the dystrophy; both men and women are equally likely to be affected by it. However the mean age of occurrence has been established as 25.72 years by a study entitled “Median nail dystrophy involving the thumb nail” conducted by Kota R, Pilani A, and Nair PA. Diagnosis is made based on clinical features such as the visuals of the transverse ridges and the central depression. It is an uncommon dystrophic condition.
At times it may be confused with habit-tic deformity which comes about by the habitual picking at the proximal nail fold margin. This is often done by patients with mental illnesses such as obsessive compulsive disorder, depression and impulse control disorder. However habit-tic deformity is not the same as median nail dystrophy. Patients with psychiatric illnesses need to be managed differently than patients of median nail dystrophy. A psychiatrist may be required to do a full evaluation of the patient before prescribing medication and behavioural counselling.
The prognosis for median nail dystrophy caused by physical trauma is usually quite good. While the pathogenesis of the disorder is unknown, treatment is highly effective. A combination of topical ointment such as tazaotene 0.05% applied to the nails at night, along with a daily dose of multivitamins can cure the disorder.
If the median nail dystrophy is attributed to the consumption of retinoid based medication, it should be discontinued. Ideally the act of discontinuing the medicine is generally enough to give the nails a chance at regeneration. If the nail does not heal even after the medication has been discontinued for a couple of months, it would be advisable to consult a dermatologist to detail a further course of action.
In addition it is advised to keep the nail length short and buff the surface of the nail to prevent the edges from catching on clothes and getting further damaged. In a matter of months after commencing the treatment, the nail plate abnormalities will begin to clear up. Regular clipping of the nail will ensure that the transverse ridges are removed without hurting the nail bed any further.
Eventually the damage to the nail bed is repaired as the pitting and splitting reduced until finally disappearing. The new nail growth is seen to be healthy and normal but despite a quick remission the condition is seen to be recurrent. Thus individuals should be advised to look out for resurfacing symptoms. Should they see longitudinal ridging lead to median splitting on the nails, they should immediately seek medical intervention.