Letters to the Editor
To the Editor:
A 10-month-old male infant, born out of nonconsanguineous parents, was referred from primary care to our dermatology department for nails thickening, acne-like lesions, and multiple steatocystomas on his face. His parents reported history of natal teeth, papules on the face, and abnormalities of nails since 2 months of age. His medical history revealed that he, initially, had episodes of erythematous swelling of nail beds of fingers and toes followed by shedding of the nails. When he was 6 months old, nails became yellowish brown, hard, angulated, and required frequent trimming. The child was given large doses of nystatin and fungicides by his primary care physician for presumed nail candidiasis, but the treatment failed. There was no similar nail and skin changes in any other family member in 2 generations. Physical examination showed that the main changes were localized in the nails and skin. He had wedge-shaped thickening with subungual hyperkeratosis and yellowish brown discoloration of all 20 nails (Fig. 1). He was found to have ill-formed lower incisors since his birth. Examination of the skin showed multiple pinhead-sized cysts, clinically consistent with steatocystomas and acne lesions located on his face (Fig. 2). These clinical findings were consistent with the diagnosis of pachyonychia congenita type 2. Pachyonychia congenita is a rare genodermatosis. Although autosomal dominant inheritance is the rule, sporadic and autosomal recessive cases are reported in literature.1 The syndrome can be divided into 2 main clinical subtypes: pachyonychia congenita type 1, also known as Jadassohn–Lewandowski syndrome and pachyonychia congenita type 2, also known as Jackson–Lawler syndrome, which are linked to mutation in genes encoding keratin 6 (K6a and K6b), 17 (K17) and 18 (K18). Pachyonychia congenita can, usually, be distinguished by clinical examination2: hypertrophic nail dystrophy, painful palmoplantar keratoderma and blistering, follicular keratoses on the trunk and extremities are common clinical features to both types of pachyonychia; oral leukokeratosis is more prominent in pachyonychia congenita type 1, instead pilosebaceous cysts (including steatocystoma and vellus hair cysts) are specific manifestations of pachyonychia congenita type 2 in addition to natal teeth and pili torti.3 There are currently no specific treatments for pachyonychia congenita. Considering the young age of the patient, we only recommended biotin 10 mg per day. In our case onychodystrophy, steatocystomas, and natal teeth let us to make a diagnosis of pachyonychia congenita type 2. In the differential diagnosis we considered: onychogryphosis, that was excluded because of the appearance of other classical features of pachyonychia; onychomycosis, that was excluded because it generally do not affect all 20 nails and it is very uncommon to find it in such a young patient (furthermore, KOH preparation and fungal cultures were negative); systemic mucocutaneous candidiasis and autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, that are more common in infants but were excluded because the patient did not have perleche, mucosal involvement, or endocrinopathy associated. Even if the hallmark of pachyonychia congenita is onychodystrophy, we focus on the development of steatocystomas during the first year of life, which is an unusual early age of onset for this feature.4,5 Sebaceous cysts of pachyonychia congenita type 2 normally appear at puberty, probably because of the pathogenetic rule played by androgens. The appearance of sebaceous cysts in such early ages let us speculate that maybe there are other environmental or genetic factors that influence the onset of steatocystomas. Unfortunately, we do not know what kind of mutation affects our patient because of the lack of infrastructure for a genetic counseling in Italy. Probably a sporadic mutation affected our patient because none of his relatives showed typical signs of this syndrome. It is interesting to note that the patient also suffered from acne infantum, which possibly might be either a chance occurrence or a new association of pachyonychia congenita.
1. Haber RM, Rose TH. Autosomal recessive pachyonychia congenita. Arch Dermatol. 1986;122:919–923.
2. Leachman SA, Kaspar RL, Fleckman P, et al.. Clinical and pathological features of pachyonychia congenita. J Investig Dermatol Symp Proc. 2005;10:3–17.
3. Liao H, Sayers JM, Wilson NJ, et al.. A spectrum of mutations in keratins K6a, K16 and K17 causing pachyonychia congenita. J Dermatol Sci. 2007;48:199–205.
4. Feng YG, Xiao SX, Ren XR, et al.. Keratin 17 mutation in pachyonychia congenita type 2 with early onset sebaceous cysts. Br J Dermatol. 2003;148:452–455.
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5. Besser FS Pachyonychia congenita with epidermal cysts and teeth at birth: 4th
generation. Br J Dermatol. 1971;84:95–96.