Schimmelpenning-Feuerstein-Mims Syndrome
A number sign (#) is used with this entry because Schimmelpenning-Feuerstein-Mims (SFM) syndrome can be caused by postzygotic somatic mutation in the HRAS (190020) gene on chromosome 11p15, the KRAS (190070) gene on chromosome 12p12, or the NRAS gene (164790) on chromosome 1p13.
Isolated nevus sebaceous (see 162900) can be caused by somatic mutation in several genes, including HRAS and KRAS.
DescriptionSchimmelpenning-Feuerstein-Mims syndrome, also known as linear sebaceous nevus syndrome, is characterized by sebaceous nevi, often on the face, associated with variable ipsilateral abnormalities of the central nervous system, ocular anomalies, and skeletal defects (summary by Happle, 1991 and Ernst et al., 2007). The linear sebaceous nevi follow the lines of Blaschko (Hornstein and Knickenberg, 1974; Bouwes Bavinck and van de Kamp, 1985). All cases are sporadic. The syndrome is believed to be caused by an autosomal dominant lethal mutation that survives by somatic mosaicism (Gorlin et al., 2001).
Clinical FeaturesFeuerstein and Mims (1962) described 2 unrelated patients with linear nevus sebaceous of the midline of the face associated with epilepsy, focal EEG abnormalities, and mental retardation. Mehregan and Pinkus (1965) outlined the natural history of organoid nevi. The first stage is characterized by alopecia with absent or primitive hair follicles and numerous small hypoplastic sebaceous glands. At puberty, the lesions become verrucous with hyperplastic sebaceous glands. Benign or malignant tumors develop in later stages.
Zaremba (1978) reviewed 37 reported cases of this disorder, described under different terms and eponyms. He also reviewed an original 19th century publication of Jadassohn and concluded that it was so good and extensive that his name deserved being attached to the disorder. He proposed that the condition be termed 'Jadassohn naevus phakomatosis' (JNP). Zaremba et al. (1978) reported 2 cases from their own experience. One of the patients required neurosurgical intervention, and histologic changes in the brain were reported.
Baker et al. (1987) reported 4 patients with epidermal nevus syndrome and neurologic manifestations, including mental retardation, seizures, ophthalmologic anomalies, intracranial aneurysm, and porencephalic cyst. A review of 60 reported cases suggested that central nervous system complications were more likely associated with epidermal nevi on the head and that the anomalies were most often ipsilateral to the skin lesion.
Monk and Vollum (1982) reported mother and daughter with nevus sebaceous of Jadassohn of the scalp. They suggested that this was the first familial occurrence reported. A similar condition, inflammatory linear verrucous epidermal nevus, was described by Hamm and Happle (1986) in mother and daughter. In a black man, his daughter and a granddaughter, Sahl (1990) described nevus sebaceus of the scalp. A basal cell carcinoma had arisen in the nevus in the grandfather. Benedetto et al. (1990) described the disorder in a boy and his maternal half brother.
Dodge and Dobyns (1995) described a girl, born of unrelated parents, with sebaceous nevus syndrome, hemihypertrophy, coloboma of the left iris, talipes equinovarus, genu recurvatum, syndactyly 3-4 on the left foot, left hemimegalencephaly, and pachygyria. In addition, Dandy-Walker malformation and agenesis of the corpus callosum were found on cranial MRI. Consistent with the proposal by Happle (1991), Dodge and Dobyns (1995) suggested that sebaceous nevus syndrome may be caused by mosaic mutation of a gene that would be lethal if expressed in all cells.
Heike et al. (2005) described a 19-year-old man with epidermal nevus syndrome who had right-sided linear skin lesions, generalized weakness, diffuse osteopenia associated with hypophosphatemic rickets, and distinctive focal bone lesions ipsilateral to the skin findings. The patient did not have the typical radiographic or histopathologic findings of fibrous dysplasia, although his circulating FGF23 (605380) level was elevated; screening of the GNAS gene (139320) revealed no mutation. Heike et al. (2005) reviewed 33 reported cases of ENS and systemic skeletal disease and found 8 (24%) involving distinctly asymmetric bone disease with more severe changes ipsilateral to the skin lesions. Heike et al. (2005) suggested that the focal skeletal disease, although different from fibrous dysplasia, may be a source of FGF23 in ENS.
Hoffman et al. (2005) reported a 17.5-year-old man of Korean ancestry who had onset of linear nevus sebaceous syndrome before age 1 year. At 7 years of age, he developed hypophosphatemic rickets and exhibited a learning disability and an attention deficit disorder. Laboratory studies showed elevated plasma FGF23, a phosphaturic peptide. Treatment with the somatostatin (SST; 182450) agonist octreotide and excision of the nevus resulted in normalization of plasma FGF23 and clinical improvement. In addition, the patient had increased serum IgE levels, which decreased somewhat after octreotide and surgery. Hoffman et al. (2005) suggested that the hypophosphatemic rickets observed in linear nevus sebaceous syndrome is a type of tumor-induced osteomalacia resulting from a tumor-produced phosphaturic substance, and suggested that FGF23 and perhaps IgE are the mediators.
Ernst et al. (2007) reported a 5-year-old girl with Schimmelpenning syndrome. She had an extensive, darkly pigmented, verrucous skin patch involving a large portion of the left side of her face and a smaller similar lesion on the right side. She also had a linear verrucoid lesion of the facial midline extending from the hairline to the chin. Neurologic involvement included blindness, seizures, and developmental delay. She presented with large mass in the left maxilla that was surgically removed and shown to be a central giant cell granuloma. About 1 year later, she developed a swelling on the right side of her face. Pathology showed foci of central giant cell granulomas and complex fibroosseous lesions in the maxilla, and an adenomatoid odontogenic tumor in the mandible. Hard tissue specimens from the mouth showed irregular accumulations of enamel, dentin, cementum, and pulp tissue, consistent with odontomas and foci of globular mineralized dentin. She also had multiple pigmented malformed teeth. Cytogenetic analysis of tissue from the second operation showed a complex karyotype with 62 to 68 chromosomes per cell; every chromosome pair had numerical or structural alterations. Eleven months later, another central giant cell granuloma was excised from the left maxilla.
Zutt et al. (2003) reported a 52-year-old woman with Schimmelpenning-Feuerstein-Mims syndrome and hypophosphatemic rickets. At birth she was noted to have a large, right-sided nevus sebaceous following the lines of Blaschko and extending to her head, neck, arm, and trunk. The scalp was also involved, resulting in alopecia. The patient developed recurrent syringocystadenoma papilliferum and basal cell carcinoma within the nevus. Other features included generalized growth retardation, bone deformation due to rickets, exotropia and ophthalmoplegia of the left eye, corneal clouding, xanthelasmata on the eyelids, and precocious puberty. Intelligence was normal. She was treated with multiple dermabrasions over the years. Phosphaturia disappeared after a long period of time, and Zutt et al. (2003) postulated that a phosphaturic factor may have been produced by the nevus. There was no family history of a similar disorder.
InheritanceSchimmelpenning-Feuerstein-Mims syndrome is believed to be caused by an autosomal dominant lethal mutation that survives by somatic mosaicism. All reported cases have occurred sporadically (Gorlin et al., 2001).
Schworm et al. (1996) reported a pair of 5-year-old Turkish monozygotic twin girls discordant for SFM syndrome. The affected girl was noted at birth to have a right-sided skin nevus on the temple, and bilateral but asymmetric keratoconjunctival dermoids, more severe on the right. Skull radiographs were normal. At age 5 years, she had skin lesions limited to the scalp with associated frontoparietal alopecia. The right eye was more severely involved, with decreased visual acuity and esotropia. Mental development was age-appropriate. The other twin showed no signs of the disorder. The report supported the concept of a postzygotic somatic mutation in the etiology of the syndrome.
Rijntjes-Jacobs et al. (2010) reported a second case of monozygotic twins discordant for SFM syndrome. The male monochorionic-diamniotic twins were born of a Dutch mother. The affected infant was noted to have several yellowish plaque skin lesions along the lines of Blaschko on the face, and severe eye abnormalities, including cryptophthalmus, coloboma, microcornea, and epibulbar lipodermoids. There was also a cleft palate and patent ductus arteriosus, and brain imaging suggested cerebral atrophy and calcifications. The child died on day 16 of life. The other twin was normal. The findings provided evidence for a postzygotic mutation as a pathogenetic mechanism.
PathogenesisHapple (1986) suggested that this condition may be explained by a dominant lethal gene arising as a somatic mutation in the early embryo or a gametic half-chromatid mutation and surviving by mosaicism. The experimental model in mice is the rescue of a lethal genotype by chimerism with a normal embryo (Bennett, 1978). Happle (1986) suggested a similar mechanism for the Proteus syndrome (176920) and the McCune-Albright syndrome (174800).
Kousseff (1992) posited that JNP is, like other phakomatoses, a paracrine growth regulation disorder or paracrinopathy, i.e., dysregulation of paracrine growth and of transforming growth factors at cellular and extracellular matrix levels, leading to localized over- and undergrowth anomalies. For the deficiencies, he adopted the term used by Gomez (1988), i.e., hamartias, parallel to the term hamartomas. He reviewed 13 cases, including one of extraordinarily severe and widespread distribution.
Molecular GeneticsGroesser et al. (2012) analyzed tissue from 2 unrelated patients with Schimmelpenning-Feuerstein-Mims syndrome for RAS hotspot mutations. One patient (Zutt et al., 2003) carried a mutation in the HRAS gene (G13R; 190020.0017) and the other patient (Rijntjes-Jacobs et al., 2010) carried a mutation in the KRAS gene (G12D; 190070.0005). In both patients, the mutations were present in lesional tissue, including nevus sebaceous, but not in nonlesional skin or blood leukocytes, consistent with a somatic mosaic state. Functional analysis of mutant cells carrying the HRAS G13R mutation showed constitutive activation of the MAPK (see 176948) and PI3K (see 171834)/AKT (164730) signaling pathways. Somatic mutations in the HRAS and/or KRAS genes were also found in 97% of 65 isolated sebaceous nevi tissues. The authors postulated that the mosaic mutation likely extends to extracutaneous tissues in SFM compared to isolated sebaceous nevi, which could explain the phenotypic pleiotropy.
Lim et al. (2014) identified a somatic NRAS mutation (Q61R; 164790.0002) in a 7-year-old Caucasian female who presented at birth with linear epidermal nevi on the left side of her body as well as dysplastic bone with a sclerotic appearance of the femur.