Pachyonychia congenita

Pachyonychia congenita is an autosomal dominant congenital hereditary disease whose leading symptoms are onychauxis, as well as painful keratomas on the palm.

The disease manifests after birth, but can also occur later.

There are 3  subtypes:

1. The nails grow to normal length, showing a prominent distal hyperkeratosis, through which one can look upwards.

2. The nails end too short, and leave exposed fingertips and distally a hyperkeratotic area.

3. Thin nail plates with little or no hyperkeratosis.

The age of onset is childhood, starting from Plantares Keratoderma, followed by the formation of leukokeratosis of the oral cavity, keratosis around the waist, elbows, and knees, as well as the sweating of the palms and soles, the formation of a hoarse voice by axillary or ingueline cyst formation, and steatocystoma.

The PC is caused by dominant-negative mutation in at least four genes (KRT6A, KRT6B, KRT16, KRT17) that are encoded by keratins. The PC-K6a, PC-K6b, PC-K16 and PC-K17 differ in the subgroups.