Multiple pilomatricomas: Cutaneous marker for myotonic dystrophy
Published Web Locationhttps://doi.org/10.5070/D361d9v7jm
Multiple pilomatricomas: Cutaneous marker for myotonic dystrophyUniversity of California, Los Angeles, Division of Dermatology, Los Angeles, California. email@example.com
Quyn J Sherrod MD, Melvin W Chiu MD, Miguel A Gutierrez MD
Dermatology Online Journal 14 (7): 22
We report an interesting case of multiple pilomatricomas (MPs) in a patient with myotonic dystrophy. Pilomatricoma (calcifying epithelioma of Malherbe) is a benign tumor of hair matrix derivation. It usually occurs as a solitary, firm, asymptomatic nodule on the face, neck, or proximal upper extremity. Most pilomatricomas have activating mutations in the ß-catenin gene (encoded by CTNNB1), leading to involvement of the WNT signaling pathway. The resulting gene product activates transcription leading to tumorigenesis . Since the onset of MPs may precede the signs of myotonic dystrophy, they can serve as potential early cutaneous markers for this systemic disease.
A 44 year-old Caucasian male presented for evaluation of 2 nodules on the scalp of 6 months duration. The nodules were firm, mobile, nontender, and ranged from 0.5 to 1.8 cm. The patient reported having 1 nodule removed 3 years before presentation. His past medical history was significant for myotonic dystrophy diagnosed clinically by EMG nerve conduction studies 12 years prior. He subsequently developed atrial flutter, bilateral cataracts, and sleep apnea. Myotonic dystrophy type 1 was confirmed by genetic analysis demonstrating 881 CTG repeats. His family history was significant for myotonic dystrophy in his father, brother, and sister. A second brother and sister were unaffected.
The nodules were excised and sent for histologic analysis. The histology of all 3 nodules revealed circumscribed neoplasms within the dermis composed of islands of basophilic cells and ghost cells, consistent with the diagnosis of MPs.
The prevalence of MPs in patients with myotonic dystrophy is greater as compared to that of the general population. These patients are more likely to present with multiple tumors and to have familial occurrence . Myotonic dystrophy type 1, also known as Steinert disease, is the most common form of adult onset muscular dystrophy. It is characterized by alteration in the skeletal muscle, lens, heart, skin, bone, and central and peripheral nervous systems. The clinical manifestations are highly variable. Steinert disease is caused by a mutation in the dystrophia myotonica protein kinase (DMPK) gene on chromosome 19. This mutation leads to amplication of an unstable trinucleotide (CTG) repeat in the 3'-untranslated region on the DMPK gene. A more severe course and earlier onset of disease is predicted with increased number of CTG repeats .
The higher frequency of pilomatricomas in Steinert disease may result from the role of DMPK in calcium regulation. In the epidermal cells, calcium influences cellular differentiation. At low intracellular calcium levels, cell proliferation is high, yet terminal differentiation is low . A mutation in DMPK within epidermal tissue leading to altered cellular proliferation may account for the higher rate of hair matrix derived tumors observed. These lower rates of terminal differentiation may correlate with the presence of transitional cells and shadow cells that characterize pilomatricoma histology. Activating mutations in the ß-catenin gene involved with the development of pilomatricomas may be a direct result of aberrant mRNA splicing or due to interactions of mutant RNA accumulations that have been proposed in the pathogenesis of myotonic dystrophy. Future investigation of the presence and role of DMPK in epidermal tissue has been previously proposed, but there are no reported results in the literature to date.
For patients with known systemic disease, this association can serve as an early diagnostic tool that may spare patients unnecessary concerns or surgical procedures. In patients with multiple pilomatricomas alone, this association should raise concerns for the subsequent development of myotonic dystrophy and warrants genetic screening of tissue or blood samples.
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