In 1968, Solomon et al¹ coined the term “epithelial nevus syndrome” as a single entity containing a group of disorders characterized by the coexistence of epidermal nevi and extracutaneous anomalies. More recently, it has become obvious that the original concept of that term was erroneous and contained several different entities that could be distinguished by the type of associated epidermal nevus and by the criterion of heritability in some of them.²,³ Genetic mosaicism in this group of diseases results in different syndromes, all of which include epidermal nevi.³ Each syndrome presents a different phenotype with a spectrum of abnormalities. These can vary from isolated epidermal nevus with no other manifestations to epidermal nevi with multiple organ involvement.² The best known epidermal nevus syndromes include Proteus syndrome, CHILD syndrome, nevus comedonicus syndrome, pigmented hairy cell nevus syndrome, and nevus sebaceous syndrome.⁴

Nevus sebaceous of Jadassohn (NSJ) is one of the nine well-defined groups of epidermal nevus syndrome⁵ and was comprehensively described in 1957 by Schimmelpenning.⁶ This phenotype is the best known of the epidermal nevus syndromes and is still referred to as epidermal nevus syndrome by some authors.⁷,⁸ The terminology of this birth defect is further confused with other names applied to it in the medical literature, such as Schimmelpenning syndrome, Feuerstein-Mims syndrome, Schimmelpenning-Feuerstein-Mims syndrome, Solomon syndrome, Jadassohn nevus phacomatosis, Jadassohn-Schimmelpenning-Feuerstein-Mims syndrome, organoid nevus phacomatosis, organoid nevus syndrome, sebaceous nevus syndrome, linear sebaceous nevus syndrome, and Jadassohn sebaceous nevus syndrome.⁵

NSJ represents a congenital hamartoma of the pilosebaceous follicular unit. The clinical features were mentioned in 1895 by the dermatologist Josef Jadassohn,⁹ who referred to this condition as “organoid nevus” to describe the combination of sebaceous gland changes with nevi. Later, the term “NSJ” was established for lesions of the facial skin characterized by sebaceous gland enlargement. The condition affects approximately 0.3% of newborns. The incidence is equal between males and females and it affects all races and ethnicities. Overall, nevus sebaceous appears as a solitary lesion right after birth, or it may appear sometime before puberty. However, the classic features may not fully develop until after puberty.¹⁰ Clinical features include an epidermal nevus of the sebaceous type on the head and neck area, with ocular and neurological abnormalities.¹¹,¹² Ocular findings can include epibulbar choristomas, corneal pannus, colobomas of the eyelid, iris, retina, choroid, or optic nerve, macrooptic discs, and optic nerve hypoplasia.¹³,¹⁴,¹⁵,¹⁶,¹⁷,¹⁸,¹⁹ The major neurological features are mental retardation, seizures, hemiparesis, quadriparesis, hypotonia, reflex abnormalities, gait disorders, diencephalic syndrome, and microcephaly.²⁰,²¹,²² Structural abnormalities seen on neuroimaging include hemimegalencephaly, gyral malformations, enlarged ventricles, intracerebral calcification, intracranial vascular abnormalities, porencephalic cysts, and, rarely, intracranial tumors including astrocytoma, pineal germinoma, choroid plexus papilloma, and lipoma of the corpus callosum.²⁰,²³ Previous estimates of neurologic abnormalities were approximately 15%,¹² but in a larger study of 196 patients with sebaceous nevi, the incidence was less than 7%.²⁴

A variety of tumors can arise within NSJ. In an evaluation of 21 reviews involving 4823 cases of nevus sebaceous, benign tumors developed in 16% of cases (range 0%-51%) and malignant tumors developed in 8% of cases (range 0%-22%).²⁵ Benign tumors included pilar, sebaceous, apocrine, and eccrine neoplasms, such as trichoblastoma and
tricholemmoma, sebaceous adenoma, tubular apocrine adenoma, syringocystadenoma papilliferum, syringoma, and nevocellular nevus.²⁶ Cutaneous horn arising from an NSJ has also been described.²⁷

Malignant tumors often begin with the sudden appearance of discrete, large, often ulcerating nodules.²⁸,²⁹ They may include basal cell, squamous cell, and sebaceous carcinoma; apocrine carcinoma; adnexal carcinoma; and eccrine porocarcinoma.²⁶,³⁰ The vast majority of the malignant lesions reported have been basal cell carcinoma (BCC). Earlier published studies reported a higher incidence of both benign and malignant tumors compared with later studies published after 1990. Cribier et al³¹ published a retrospective study of 596 nevus sebaceous cases and reported a 0.8% incidence of BCC, with more than 90% of the other tumors being trichoblastomas.³¹ They described a common histologic change consistent with benign epidermal hyperplasia and suggested that many previously reported cases of BCC arising in this condition were really benign trichoblastomas. Of the true malignant neoplasms associated with NSJ, BCC is by far the most common, followed by squamous cell carcinoma. Occasionally, more than one malignant lesion can occur in the same NSJ lesion. Although most of these tumors develop during adulthood, malignancies have been reported in children younger than 18 years.³²,³³,³⁴,³⁵,³⁶,³⁷,³⁸

While NSJ is not usually considered to be an inherited disorder, West et al³⁹ reported three cases localized to the scalp in a mother and two daughters, supporting an underlying genetic association with an autosomal dominant transmission.