Pachyonychia congenita type 1: classical presentation of a rare disease

Pachyonychia congenita (PC) is a very rare group of autosomal dominant genodermatoses caused by mutations in one of the genes that encode for nail keratin [1]. It has traditionally been classified into four types, with type 1 (Jadassohn-Lewandowsky type) and type 2 (Jackson-Lawler type) being the most common variants. We present here a case of PC type 1 with classical features.
A 19-year-old male patient presented to us with a history of thickened nails since the age of 1.5 months and painful thickenings of the soles since the age of 3 years. He gave a history of development of recurrent painful fluid-filled lesions over the soles. There was no history of consanguineous marriage in the parents, and antenatal/birth history and postnatal development were uneventful. There was no history of similar disease in the family. There was no history of hoarseness of voice. On examination, the patient had brownish discoloration and dystrophy of the finger and toe nails with extensive subungual hyperkeratosis leading to elevation of the distal ends of the nail plates (fig. 1). There were multiple ill-defined hyperkeratotic plaques present over the soles (fig. 2). Oral mucosa showed a white-colored, non-tender and non-scrapable plaque on the dorsal surface of the tongue (fig. 3). The rest of the cutaneous and systemic examination was normal. Routine investigations including hemogram, liver and renal profiles were normal. KOH mount of the nail clippings was negative for fungal elements. Skin biopsy from the sole revealed orthohyperkeratosis and acanthosis. Based on the history, suggestive clinical features and histopathology, a diagnosis of PC type 1 was made and the patient was treated symptomatically. However, gene analysis was not done due to the lack of resources.
Pachyonychia congenita was first recorded by Muller in 1904, and this was followed by published case reports by Wilson (1905) and Jadassohn and Lewandowsky (1906) [2]. Around 700 cases of PC have been reported since then [3]. Most cases have an autosomal dominant inheritance, but autosomal recessive inheritance has also been reported [4]. The disease is caused by mutations in one of the five keratin genes, namely KRT6A (38%), KRT16 (33%), KRT17 (17%), KRT6B (9%) and KRT6C (3%), with clinical features depending on the gene involved and the site of mutation in the genes [3]. In fact, the disease is now classified into five types on the basis of the above five genes involved [5]. This...


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