一名39岁的白人妇女在RAF1中受Noonan综合征(NS)突变的影响,她的四肢出现了两个月前的瘙痒病变。临床上,有多个脐状丘疹,中央角化过度,位于上肢和下肢(图1,a-b)。患者无糖尿病病史,无慢性肾功能衰竭,但患有肥厚型心肌病.血液检查没有异常。在皮肤病变的组织学检查中,观察到带有过度角化口的外生毛囊与毛发碎片,炎症细胞,和表皮穿孔。建立了Kyrle病(KD)的最终诊断。患者接受窄带UVB(NB-UVB)光疗,伴有残留的萎缩性疤痕(图1,c-d),但症状也得到了完全和持久的缓解。KD属于穿孔性皮肤病(PD),一组异质的皮肤疾病,其特征是真皮成分的经表皮消除。尽管PD的分类一直在争论,传统上公认的四种主要形式:反应性穿孔胶原病,穿行弹性纤维变性,穿孔性毛囊炎,KD(1)。KD的典型皮肤表现是圆顶状丘疹和结节的萌出,带有发白的中央角化塞,主要位于四肢和臀部。Kyrle在1916年描述,KD经常与全身性疾病有关,尤其是慢性肾功能衰竭和糖尿病。其他相关疾病包括慢性肝病,内部恶性肿瘤,充血性心脏病(1)。尽管没有达成共识,基础疾病的控制仍然是第一个治疗目标。两者都是局部的(角质层分离剂,类维生素A,和皮质类固醇)和全身治疗(皮质类固醇,类维生素A,抗生素,和光疗)已被报道可以控制皮肤表现(2)。根据我们的经验,NB-UVB是弥漫性病变的一线治疗的有效选择,在KD和其他PD中(3)。NS是一种相对常见的放射病,一组异质性的遗传疾病,其特征是Ras-丝裂原活化蛋白激酶(Ras-MAPK)途径的缺陷,估计患病率为1/1000-2500。PTPN11是最常见的突变基因,占50%的病例,但超过十种基因被鉴定为导致NS(4)。古典特征包括独特的面部畸形,身材矮小,肺动脉瓣狭窄,和其他不同器官的异常。皮肤是常见的。角质化疾病和毛发异常,如毛发角化病,光敏性红斑,波浪形或卷发,和稀缺的头皮头发经常被描述。其他皮肤症状包括容易瘀伤,皮肤松弛过度,多个舌头,和咖啡色斑点(5)。据我们所知,迄今为止,尚无NS患者的KD病例报道.KD的确切病因尚不清楚,但有人假设全身性疾病,比如糖尿病和慢性肾衰竭,会导致物质沉积或真皮改变,这引发炎症过程与随后的经表皮挤压(1)。在我们的病人身上,我们排除了所有与KD相关的原因。然而,这种表现可能是我们病人患病的直接结果。我们的病人患有弥漫性毛发角化病,KD的可能致病机制之一被认为是异常的表皮角质化和继发性炎症皮肤反应(1)。另一方面,NS典型皮肤的过度松弛和脆性表明存在改变的结缔组织,这可能会引发异常的角质化,随后,经表皮挤压,以及穿孔性弹性纤维变性,并与遗传性结缔组织疾病相关(1)。此外,我们的病人患有心脏病,与KD(5)相关的另一个条件。虽然这些解释有其吸引力,目前没有足够的证据表明KD和NS之间有联系,有必要收集更多的数据来证实这一假设。
A 39-year-old Caucasian woman affected by Noonan Syndrome (NS) mutated in RAF1 was referred to us with itchy lesions on her limbs that had appeared two months earlier. Clinically, there were multiple umbilicated papules with a hyperkeratotic central plug, localized on the upper and lower limbs (Figure 1, a-b). The patient had no personal history of diabetes mellitus and no chronic renal failure, but suffered from hypertrophic cardiomyopathy. Blood tests showed no abnormalities. On histological examination of a skin lesion, an ectatic hair follicle with hyperkeratotic ostium was observed with fragments of hair, inflammatory cells, and epidermal perforation. A final diagnosis of Kyrle\'s disease (KD) was established. The patient underwent narrowband UVB (NB-UVB) phototherapy with residual atrophic scars (Figure 1, c-d) but with complete and long-lasting resolution of symptoms as well. KD belongs to perforating dermatoses (PD), a heterogeneous group of skin diseases characterized by the transepidermal elimination of dermal components. Despite the classification of PD being debated, four primary forms are traditionally recognized: reactive perforating collagenosis, elastosis perforans serpiginosum, perforating folliculitis, and KD (1). The typical skin manifestation of KD is an eruption of dome-shaped papules and nodules with a whitish central keratotic plug, mainly localized on the extremities and the buttocks. Described by Kyrle in 1916, KD is frequently associated with systemic diseases, especially chronic renal failure and diabetes mellitus. Other associated conditions include chronic hepatic disease, internal malignancies, and congestive heart disease (1). Despite the absence of a consensus, the control of the underlying disease remains the first therapeutic target. Both topical (keratolytics, retinoids, and corticosteroids) and systemic treatments (corticosteroid, retinoids, antibiotics, and phototherapy) have been reported to control skin manifestations (2). In our experience, NB-UVB is an effective option as first-line therapy in case of diffuse lesions, both in KD and in other PDs (3). NS is a relatively common RASopathy, an heterogenous group of genetic disease characterized by a defect of the Ras-mitogen-activated protein kinase (Ras-MAPK) pathway, with an estimated prevalence of 1/1000-2500. PTPN11 is the most frequent mutated gene, accounting for 50% of cases, but more than ten genes were identified as causing NS (4). Classical features include a distinctive facial dysmorphism, short stature, pulmonic stenosis, and other anomalies of different organs. The skin is commonly involved. Keratinization disorders and hair abnormalities such as keratosis pilaris, ulerythema ophryogenes, wavy or curly hair, and scarce scalp hair are often described. Other cutaneous signs include easy bruising, skin hyperlaxity, multiple lentigines, and café-au-lait spots (5). To the best of our knowledge, no cases of KD in patients with NS have been previously reported to date. The exact etiopathogenesis of KD is not clear, but it was hypothesized that systemic diseases, such as diabetes and chronic renal failure, can cause a deposit of substances or dermis alterations, which triggers the inflammatory process with subsequent transepidermal extrusion (1). In our patient, we ruled out all the causes commonly associated with KD. It is however possible that this manifestation could be a direct result of our patient\'s illness. Our patient suffered from diffuse keratosis pilaris, and one of the possible pathogenetic mechanisms of KD was theorized to be an abnormal epidermal keratinization with a secondary inflammatory dermic response (1). On the other hand, the hyperlaxity and fragility of the skin typical of NS suggest the presence of altered connective tissue, which could trigger an abnormal keratinization and, subsequently, the transepidermal extrusion, as well as perforating elastosis, and is associated with genetic connective tissue diseases (1). Moreover, our patient suffered from a cardiac disease, another condition associated with KD (5). Although these explanations have their appeal, there is currently insufficient evidence of a link between KD and NS, and it will be necessary to collect additional data to confirm this hypothesis.