Dermatology Online Journal

Autosomal dominant transmission of nevus sebaceous of Jadassohn
Cameron West MD, Swetha Narahari BS, Shawn Kwatra MD, Steven Feldman MD PhD
Dermatology Online Journal 18 (11): 17

Wake Forest University Health Sciences, Winston-Salem, North Carolina

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Abstract

BACKGROUND: Nevus sebaceus of Jadassohn is a complex congenital hamartoma that has a predominant sebaceous component. It presents as waxy, well-circumscribed, yellow plaques localized to the head and neck. Its genetic etiology has more often been described as sporadic, with scattered cases featuring autosomal dominant transmission also reported. The development of benign tumors within the lesions is a well-known phenomenon and requires clinical surveillance for new growths suggesting malignant transformation. MAIN OBSERVATIONS: We report three cases of nevus sebaceus of Jadassohn localized to the scalp in a mother and her two daughters. CONCLUSIONS: This case further supports the underlying genetic association in familial cases of NSJ, specifically autosomal dominant transmission.

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Introduction

Nevus Sebaceus of Jadassohn (NSJ) is a relatively uncommon, predominantly sebaceous hamartoma, with an estimated incidence of less than 1/100,000 [1]. Classically, NSJ presents as a waxy, hairless, verrucous plaque located on the scalp, face, or neck. Historically, there is an association of basal cell carcinoma arising within NSJ, which resulted in the recommendation of prophylactic excision. A retrospective analysis of 596 cases demonstrated an extremely low rate of malignant tumors within NSJ. Basal cell carcinoma occurred in 0.8 percent of cases. Trichoblastoma, a benign follicular tumor, was the most common tumor arising within NSJ, present in approximately 4.7 percent of cases [2]. Whereas NSJ is typically congenital, many cases become clinically apparent around puberty, suggesting a hormonal influence [3, 4]. Most cases of NSJ appear to be sporadic, but several case reports suggest a dominant genetic transmission [5, 6, 7]. We report a case of NSJ in a seven-year-old female that is also present in her sister and mother.

Case report

Figure 1

A seven-year-old female patient was referred to the dermatology department for evaluation of a scalp lesion. Physical examination demonstrated a round, well-circumscribed, approximately 2.5 x 2.5 cm pink, hairless, verrucous plaque along the posterior vertex of the scalp (Figure 1). Further history revealed that the patient’s sister and mother had similar scalp lesions (Figures 2 and 3, respectively). Biopsies were not performed.

Figure 2	Figure 3

Discussion

NSJ was thought to be caused by sporadic genetic mutations until 1982, when Monk et al. presented the first report of a genetic association of NSJ in a mother and daughter [6]. In 1990, Sahl reported a familial case of NSJ affecting three consecutive generations. Further, in 1998 Fearfield reported NSJ in a father and his two sons. The discovery of these cases suggests an autosomal dominant mechanism for the familial inheritance of NSJ [5, 8].

However, there have also been reports of familial cases not conforming to a classical Mendelian inheritance pattern. NSJ was reported in 10-year-old dizygotic male twins and in an 8-year-old boy and his 6-year-old sister, with no family history of NSJ [1, 7]. It is highly unlikely for sporadic mutations to account for such familial cases in which the classic autosomal dominant inheritance pattern is not observed. A ‘paradominant’ inheritance theory was proposed [9]. In this pattern of transmission individuals that are heterozygous for the underlying gene are phenotypically normal and pass the mutated allele clinically undetected to subsequent generations. The mutated allele presents with phenotypic significance only when a postzygotic mutation in early embryogenesis results in loss of the wild-type allele resulting in a mosaic of either the homozygous or hemizygous state of the mutated allele. This mode of transmission accounts for clusters of familial cases in which parents are phenotypically normal and offspring manifest the skin lesions of NSJ [9].

Conclusion

We report an unusual case of NSJ arising in a mother and two daughters. All three lesions were located on the scalp. The mother and two daughters otherwise had no abnormalities. The likelihood of encountering three family members with sporadic NSJ is exceedingly unlikely. Our case adds to the number of cases of familial NSJ. This case, however, supports earlier reports in which an autosomal dominant mode of transmission is suspected.

References

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