Hypohidrotic ectodermal dysplasia (HED) is found worldwide with an estimated incidence of 1 per 100,000 births. X-linked hypohidrotic ectodermal dysplasia (XLHED, OMIM 305100) is the most common form of the ectodermal dysplasias (ED), a rare group of hereditary diseases characterized by abnormal development of eccrine sweat glands, hair, and teeth. Heterozygous carriers of XLHED often manifest minor or moderate degrees of hypotrichosis, hypodontia, and hypohidrosis. ED1, the gene for XLHED encodes ectodysplasin A, which is a new member of the tumour necrosis factor family. The majority of mutations in XLHED are missense mutations, but one-fifth are insertion/deletions. Here we report a novel 7-bp deletion mutation (nt1242-1248) in exon 9 of the ED1 gene that results in a frameshift and premature stop codon (PTC + 38 amino acids). Mutation analysis in families with XLHED allows for genetic counselling, prenatal diagnosis and confirmation of carrier status.

Congenital self-healing reticulohistiocytosis (CSRH), a rare benign variant of Langerhans cell histiocytosis (LCH), is characterized by (a) congenital skin lesions, (b) a healthy infant with no systemic involvement, (c) the histopathologic finding of a Langerhans cell infiltrate and (d) spontaneous involution within the first year of life without sequelae. We report a Taiwanese girl born with widespread hemangioma-like lesions. The diagnosis of LCH was confirmed by finding a diffuse dermal infiltrate of S-100-protein- and OKT6 (CD1a)-positive mononuclear cells and the presence of Birbeck granules in 10% of the mononuclear cells ultrastructurally. The diagnosis of CSRH was further established by rapid and complete involution of the lesions in 3 months. No recurrence was noted for 7 years. Our case illustrates that CSRH can mimic diffuse neonatal hemangiomatosis clinically; thus, it is important to include CSRH in the differential diagnosis of congenital or neonatal hemangiomatosis.

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