What are the other Names for this Condition? (Also known as/Synonyms)

• Arrector Pili Hamartoma of Skin
• Congenital Pilar and Smooth Muscle Nevus of Skin
• Cutaneous Congenital Smooth Muscle Hamartoma

What is Smooth Muscle Hamartoma of Skin? (Definition/Background Information)

• Smooth Muscle Hamartoma (SMH) of Skin is a benign overgrowth of smooth muscle cells on the body; a hamartoma is a developmental anomaly
• The skin lesion is uncommon and is mostly present at birth; some are (rarely) seen in older children and adults. Cutaneous Smooth Muscle Hamartomas are mostly observed on the trunk, arms, and legs
• The cause of formation of Smooth Muscle Hamartoma of Skin is unidentified. A positive family history has been occasionally observed. The presence of multiple tumors has been associated with certain genetic conditions such as Michelin Tyre Baby Syndrome and Xp Microdeletion Syndrome
• Treatment may not be generally required for a Smooth Muscle Hamartoma of Skin, unless it presents cosmetic concerns. In such cases, when treatment is necessary, surgical excision to remove the lesions may be undertaken
• The prognosis is usually excellent with suitable treatment, since these lesions are typically benign. However, the overall prognosis of Smooth Muscle Hamartoma of Skin may depend upon the severity of any associated underlying condition

Who gets Smooth Muscle Hamartoma of Skin? (Age and Sex Distribution)

• Smooth Muscle Hamartoma of Skin is an infrequently-occurring benign skin condition that commonly presents at birth (congenital in nature)
• In rare cases, it may be observed during late childhood, adolescence, or into young adulthood
• Both males and females are affected, though the incidence of Cutaneous Smooth Muscle Hamartoma is higher in males compared to females
• All racial and ethnic groups are at risk and there is no preference noted

What are the Risk Factors for Smooth Muscle Hamartoma of Skin? (Predisposing Factors)

• Currently, there are no identified risk factors for Smooth Muscle Hamartoma of Skin occurrence
• A positive family history of the condition has been occasionally noted (such as in a mother and child, in siblings, etc.)
• Other rare disorders the tumor is associated with include Xp Microdeletion Syndrome and Michelin Tire Baby Syndrome
• Infrequently, some cases have been associated with Becker’s nevus

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Smooth Muscle Hamartoma of Skin? (Etiology)

The cause of Smooth Muscle Hamartoma of Skin formation is unknown. The tumor may have a congenital origin (seen in most cases) or it may be acquired.

• In rare cases, a positive family history has been noted
• Solitary tumors are sporadic in nature and the cause is not established
• Occasionally, multiple tumors may be seen in association with various genetic disorders; in such cases, the tumors may develop due to certain genetic factors/abnormalities

What are the Signs and Symptoms of Smooth Muscle Hamartoma of Skin?

The signs and symptoms of Smooth Muscle Hamartoma of Skin may include the following:

• The presence of a single, well-circumscribed plaque or dark skin patch
• The size of the skin lesion is variable and may be between 1-10 cm
• The lesion shows a progressive growth pattern (increased size) as the child grows
• In many cases, excess hair growth may be present on or around the tumor
• The skin over the lesion may lose its vitality; atrophy may be seen in few cases
• Cutaneous Smooth Muscle Hamartomas can occur anywhere in the body; the usual sites are the head and neck region, chest, back, abdomen, buttocks, thighs, arms, etc.
• Unusual sites of presentation include the scrotum and near the eye (eyebrow and eyelid)
• The lesions are usually painless and non-itchy

Occasionally, multiple smooth muscle hamartomas may be present. In such cases, the condition may be associated with genetic disorders Xp Microdeletion Syndrome or Michelin Tire Syndrome. Other signs and symptoms of the disorder may also be noted.

How is Smooth Muscle Hamartoma of Skin Diagnosed?

A Smooth Muscle Hamartoma of Skin is diagnosed through the following tools:

• Complete physical examination with evaluation of medical history
• Dermoscopy: It is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Wood’s lamp examination: In this procedure, the healthcare provider examines the skin using ultraviolet light. It is performed to examine the change in skin pigmentation
• Skin biopsy: A skin biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• A differential diagnosis may be necessary prior to establishing a definitive diagnosis, by excluding tumors including Becker’s nevus and pilar leiomyoma

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Smooth Muscle Hamartoma of Skin?

The complications that arise from a Smooth Muscle Hamartoma of Skin may include:

• In some individuals, it may give rise to cosmetic concerns, additionally due to excessive or increased hair growth (hypertrichosis)
• In rare cases, complications that may arise from the underlying genetic disorders may be present
• Recurrence of the tumor on incomplete surgical excision

How is Smooth Muscle Hamartoma of Skin Treated?

The treatment measures for Smooth Muscle Hamartoma of Skin include:

• The healthcare provider may choose to regularly observe solitary tumors; a “wait and watch” approach may be undertaken following a diagnosis of SMH of Skin. In such cases, no treatment is generally required
• If required, a surgical excision (or laser therapy) and complete removal of the lesion, to address cosmetic issues or if its growth is worrisome, may be undertaken
• Laser therapy may also be considered for excess hair removal
• Undertaking treatment of other signs and symptoms due to an associated genetic disorder (if any)
• Follow-up care with regular screening and check-ups are important and encouraged

How can Smooth Muscle Hamartoma of Skin be Prevented?

Current medical research has not established a method of preventing the occurrence of Smooth Muscle Hamartoma of Skin.

• If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Smooth Muscle Hamartoma of Skin? (Outcomes/Resolutions)

• The prognosis of Smooth Muscle Hamartoma of Skin is excellent on its complete excision and removal
• Since, these are benign conditions, the prognosis is generally excellent even if no treatment is provided and only periodic observation maintained
• When multiple tumors are associated with Xp Microdeletion Syndrome or Michelin Tire Baby Syndrome, the overall prognosis may depend upon the severity of the syndrome

Additional and Relevant Useful Information for Smooth Muscle Hamartoma of Skin:

• There is no evidence to prove that the tumor formation is influenced by one’s dietary choices
• Cleaning the skin too hard with strong chemicals or soaps may aggravate the skin condition. Care must be taken avoid strong soaps and chemicals that could potentially worsen the condition
• The presence of dirt on the body is not a causative factor for the condition. However, it helps to be clean and hygienic, which may help the condition from getting worse