Racquet nail is a deformity resulting in a short, broad and flat nail. It usually results from the malformation of the underlying bone and soft tissues of the terminal phalanges. Isolated thumb nail deformity has been observed most commonly.
DuBois was the first to describe this nail deformity. He believed that it was a sign of congenital syphilis. Thereafter, two forms have been described: the genetic and the rare acquired form in association with hyperparathyroidism. The former involves principally the thumb. Thomsen pointed out that in unilateral cases of stub thumb, the gross cartilage plate of the anomalous phalanx is obliterated, while the corresponding one of the unaffected side is still intact.
Burrow related this anomaly to the early closure of the growth cartilaginous line of the terminal phalanx. This genetic disorder occurs mostly as an isolated anomaly and it is transmitted as an autosomal dominant trait. It may also occur in association with many syndromes.
Basset has described three different types of short nails: racquet thumb, racquet fingers and the simple short nails.
Ronchese has observed in his series of 150 patients that all the digits may be affected with the predominance of bilateral involvement.
The anomaly is a source of embarrassment especially for young women who will place the hand into a fist-position with the affected thumb or thumbs hidden.
A 20-year-old healthy male presented to our clinic with a 2 year history of asymptomatic changes of the shape of all fingers nails. The patient reported no family history of the same complaint. Physical examination showed widening and shortening of all finger nails bilaterally with the exception of little finger nails (Figs 1, 2). Toenails were spared. Plain x-ray of both hands showed low bone density in the proximal phalanges in the 2nd to 5th finger bilaterally. Blood tests showed high parathormone (PTH) (110.3 pg/mL; reference range: 15–85), serum 25-hydroxy-D3 was low (<10.0 nmol/L; reference range ≥ 75); TSH, T3, T4, calcium, phosphorous and creatinine were within normal limits. The diagnosis of acquired racquet nails (brachyonychia) in association with hyperparathyroidism was established.
There are very few cases of hyperparathyroidism published in the literature.[7-9] In our observation, besides the high level of PTH it was easy to rule out psoriatic arthropathy with ultrasonography and X-ray. Absence of nail biting was obvious.
It is customary to distinguish three categories of hyperparathyroidism. In primary type (the most common), there is usually autonomous secretion of PTH by a single parathyroid adenoma (90%), while carcinoma has been reported vey rarely (1%). Secondary hyperparathyroidism is present when there is hyperplasia with increased PTH reaction in an attempt to compensate for a prolonged hypocalcemia. Its effect is to restore serum calcium levels. This type is usually due to chronic renal failure, malabsorption osteomalacia and rickets. In a very small proportion of cases of secondary hyperparathyroidism, continuous stimulation of the parathyroid glands may result in adenoma formation and autonomous PTH secretion. Definition of tertiary hyperparathyroidism is a primary hyperparathyroidism developed on a hyperparathyroidism that is secondary to a hypocalcemia of a renal insufficiency. From a diagnostic point of view, it is easy to recognize because it is a hyperparathyroidism during a renal insufficiency which is no longer in hyper or normocalcemia but results in a hypercalcemia.
Radiographically, racquet nails can be associated with some characteristic changes. In early stages, subperiosteal demineralization can be noted in the phalanges. This may be followed by resorption of the terminal phalanges with occasional appearance of acroosteolysis. This is particularly true in ‘brown tumour’ of hyperparathyroidism which can be indistinguishable from giant cell bone tumour and giant cell reparative granuloma of the bone upon pathological analysis.
Beside the racquet nails, cyanosis of the finger tips as a result of decreased perfusion from vascular calcification may lead to gangrene of the fingers and toes. Onycholysis, pachyonychia, Muehrcke's bands, leuconychia, half-and-half nails and koilonychia may also be associated with nail changes.
In conclusion, we recommend measuring parthormone and serum 25 hydroxy-D3 in every patient with an acquired form of racquet nails.