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Year : 2005  |  Volume : 71  |  Issue : 3  |  Page : 217-218

Hyperpigmented patch on the trunk of a neonate

1 Department of Dermatology,Venereology and Leprosy, BLDEAs SBMP Medical College, Hospital and Research Centre, Bijapur, India
2 Department of Pathology, BLDEAs SBMP Medical College, Hospital and Research Centre, Bijapur, India

Correspondence Address:
Arun C Inamadar
Department of Dermatology, Venereology and Leprosy, BLDEAs SBMP Medical College, Hospital and Research Centre, Bijapur - 586103, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0378-6323.16252

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How to cite this article:
Palit A, Inamadar AC, Athanikar S B, Sampagavi V V, Deshmukh N S, Yelikar B R. Hyperpigmented patch on the trunk of a neonate. Indian J Dermatol Venereol Leprol 2005;71:217-8

How to cite this URL:
Palit A, Inamadar AC, Athanikar S B, Sampagavi V V, Deshmukh N S, Yelikar B R. Hyperpigmented patch on the trunk of a neonate. Indian J Dermatol Venereol Leprol [serial online] 2005 [cited 2020 Aug 9];71:217-8. Available from:

A one-day-old, full-term, normally delivered, female neonate was being routinely examined. A brownish irregular patch of 2 cm ´ 1.5 cm, with fine long hairs was observed on her right loin [Figure - 1]. On gentle stroking, the lesion became more prominent along with the appearance of goose bumps. A punch biopsy was taken from the edge of the lesion. Histopathological preparation on H/E stain showed mild hyperkeratosis of the epidermis and basal cell hyperpigmentation. In the reticular dermis, well-defined smooth muscle fiber bundles were seen, interspersed among hair follicles [Figure - 2]. Masson Trichrome stain [Figure - 3] confirmed the presence of smooth muscle fibers (stained red).


Answer to Quiz

Congenital smooth muscle hamartoma (CSMH) or congenital arrector pili hamartoma.

  Discussion Top

CSMH was first described by Stokes in 1923.[1] The lesions may be solitary or multiple, the former being commoner (1 in 3000 births).[2] Classically, it is present at birth or seen during the first week of life, located most commonly over the lumbo-sacral region.[2] Other sites of occurrence are buttocks, proximal extremities, and rarely the scalp.[3] Multiple lesions are rare and may occur in a linear pattern.[4],[5] Diffuse involvement may occur with the Michelin type baby syndrome.[6]

The commonest morphological pattern is a skin-colored or slightly hyperpigmented patch or plaque associated with long vellus hairs or small follicular papules all over the lesion.[2] On gentle stroking, the lesion shows vermiculation and pilo-erection (Pseudo-Darier's sign)[2],[7] or occasionally fasciculation.[2] Lesions occurring as a linear atrophic plaque[4] and a patch with perifollicular papules[5] have been reported.

CSMH is related to the arrectores pilorum muscle,[8] which in fetal life originates from a diffuse metachromatic zone of mesoderm situated near the hair germ. Over-proliferation of this region is likely to give rise to the lesion. Clinically, CSMH has to be differentiated from cafι-au-lait macule, solitary mastocytoma, congenital melanocytic nevus and connective tissue nevus.[2] Histopathologically, pilar leiomyoma is an important differential diagnosis.[8] A well-defined bundle of long, straight smooth muscle cells in the deeper dermis, which are separated from the dermal collagen by a clear space, is characteristic of CSMH. Irregular smooth muscle bundles, intermingled with collagen, which may be attached to the hair follicle, are found in pilar leiomyoma.[5],[8]

An acquired form of smooth muscle hamartoma without hyperpigmentation or excessive hair has been reported.[9] Other acquired lesions occur in association with Becker's nevus.[4] There are clinical and histopathological overlaps between Becker's nevus and CSMH.[7],[8] Some authors include both the entities in a spectrum of hamartomatous disorders,[7] involving the epidermis (hyperpigmentation), hair follicles (hypertrichosis) and the dermis (smooth muscle). Children with the diffuse form of the disease may have other congenital malformations, growth and mental retardation.[7] No treatment is necessary for solitary lesions, which may persist unchanged or there may be slight reduction of the hypertrichosis.

  References Top

1.Stokes JH. Nevus pilaris with hyperplasia of non-striated muscle. Arch Dermatol Syphil 1923;7:479.  Back to cited text no. 1      
2.Atherton DJ. Naevi and other developmental defects. In : Champion RH, Burton JL, Burns DA, Breathnach SM, editors. Textbook of Dermatology, 6th Ed. Oxford: Blackwell-Science; 1998. p. 519-616.  Back to cited text no. 2      
3.Knable A, Treadwell P. Pigmented plaque with hypertrichosis on the scalp of an infant. Pediatr Dermatol 1996;13:431-3.  Back to cited text no. 3  [PUBMED]    
4.Grau-Massanes M, Raimer S, Colome-Grimmer M, Yen A, Sanchez RL. Congenital smooth muscle hamartoma presenting as a linear atrophic plaque: Case report and review of the literature. Pediatr Dermatol 1996;13:222-5.  Back to cited text no. 4  [PUBMED]    
5.Jang HS, Kim MB, Oh CK, Kwon KS, Chung TA. Linear congenital smooth muscle hamartoma with follicular spotted appearance. Br J Dermatol 2000;142:138-42.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]  
6.Oku T, Iwasaki K, Fujita H. Folded skin with an underlying cutaneous smooth muscle hamartoma. Br J Dermatol 1993;129:606-8.  Back to cited text no. 6  [PUBMED]    
7.Albrecht S. Neoplasias and hyperplasias of neural and muscular origin. In : Freedberg IM, Eisen AZ, Wolff KW, Austen KF, Goldsmith LA, Katz SI, editors. Fitzpatrick's Dermatology in General Medicine, 6th Ed. New York: McGraw-Hill; 2003. p. 1032-41.  Back to cited text no. 7      
8.Ragsdale BD. Tumors of fatty, muscular and osseous tissue: fat as a tissue, an organ and a source of tumors. In : Elder D, Elenitsas R, Jaworsky C, Johnson B Jr., editors. Lever's Histopathology of skin, 8th Ed. Philadelphia: Lippincott-Raven; 1997. p. 457-502.  Back to cited text no. 8      
9.Darling TN, Kamino H, Murray JC. Acquired cutaneous smooth muscle hamartoma. J Am Acad Dermatol 1993;28:844-5.  Back to cited text no. 9  [PUBMED]    


  [Figure - 1], [Figure - 2], [Figure - 3]

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1 Hamartoma de músculo liso congénito: importancia de un correcto diagnóstico diferencial
C. Suárez Castañón,J. Martínez Blanco,B. Corrales Canel,M. Morán Poladura,J. Melgar Pérez
Anales de Pediatría. 2012; 77(6): 425
[Pubmed] | [DOI]


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