Sweat duct proliferation associated with aggregation of elastic tissue and atrophodermia vermiculata: a simulator of microcystic adnexal carcinoma – a family with MALTA‐syndrome

the constellation of findings of atrophodermia vermiculata includes irregular elastin aggregates and sweat gland proliferations. It affects a small group of patients and has been described under the disease names Nicolau-Balus syndrome, eccrine follicular hamartoma syndrome, bilateral facial apocrine fibrosing hamartoma, and Rombo syndrome [1–9]. From childhood onwards, affected individuals present with syringoma-like or milia-like lesions and follicular scars on the face, upper trunk, and sometimes extremities [1–3, 6, 8]. Some patients also display unilateral or bilateral infiltrated plaques on the cheeks [8, 9] (Table 1). The latter may be misinterpreted clinically and histologically as microcystic adnexal carcinoma (MAC). In 2010, Schaller and colleagues first described two patients in whom cheek lesions were initially misdiagnosed both clinically and histopathologically as MAC and were repeatedly and incompletely excised by micrographically controlled surgery [8]. These patients had bilateral plaques on the cheeks that had been present since childhood, as well as facial milia, atrophodermia vermiculata, and syringomas. The patients also had clinical and histopathologic characteristics previously described as Nicolau-Balus syndrome, Rombo syndrome, and by Peyri et al as eccrine follicular hamartoma syndrome [1, 3, 4]. On histologic examination, ductal proliferations were found extending into the deep dermis within a sclerotic stroma [8]. Clinical follow-up, which lasted up to 19 years, revealed no progression of the findings, suggesting benign behavior and hamartomatous character. The condition was therefore termed MAC-like syndrome [8]. The genetic background of these syndromes was not known until now. By genetic analysis of several symptomatic families, pathogenic variants of the MYH9 gene encoding the non-muscle myosin type IIA heavy chain (NMMIIA) have recently been identified. For this purpose, germline exome sequencing of a total of six affected individuals from three families was performed. The MYH9 variants co-segregated with the phenotype and were further sequenced. The variClinical Letter