Leiomyoma is a benign tumour commonly encountered in the genitourinary and gastrointestinal organs in adults The skin is the second most common location for leiomyoma after the uterus, hosting ~5% of all leiomyomas [1].

Cutaneous leiomyomas are rare benign tumors arising from the arrector pili muscle of hair follicles, ranging in number from a few to several hundred [2,3]. Cutaneous leiomyomas are derived from smooth muscle in the skin. Piloleiomyomas, genital leiomyomas (dartoic), and angioleiomyomas are subtypes, each having distinct origins and clinicopathologic features [4,5]. Cutaneous leiomyomas are more likely to occur in adults than in children, and often arise in the fifth and sixth decades of life [6]. These lesions may be hereditary or sporadic [7].

In the present study, we describe a case of a 30-year-old male with a two-month history of lesions in the lumbar region. During the second month, the mass was observed to have increased in size and become painful. The pain experienced may be spontaneous or as a result of exposure to cold, pressure or emotional stress on clinical examination, skin-colored nodules were observed on the back of the patient, the largest of which measured ~10 × 15 mm and was located in lumber region (Figure 1).

Figure 1: Skin-colored nodules on the back of the patient, (NB) blood drops due to injection of anesthesia.

Thorough clinical examination did not reveal any evidence of tumors located elsewhere or any pertinent past clinical history. No history of significant or hereditary diseases in the family was reported. A punch biopsy was performed by the clinician. Spindle cells with an eosinophilic cytoplasm were observed under high-power examination (Figure 2).

Figure 2: Spindle cells with an eosinophilic cytoplasm (H&E).

Immunohistochemical studies were performed and the cells stained strongly positive for smooth muscle actin (SMA) (Figure 3). As a result, the patient was diagnosed with pilar leiomyoma.

Figure 3: Immunohistochemical staining (SMA).

Cutaneous leiomyomas can occur anywhere smooth muscle exists. Piloleiomyomas originate from the arrector pili muscles of the pilosebaceous unit, and may be either multiple or solitary [8]. Solitary variants develop during adulthood (with rare congenital/pediatric exceptions), whereas multiple leiomyomas occur typically from ages 10-30 years, with these distribution being unclear in either case. Ninety percent of piloleiomyomas are painful, described as burning, pinching, or stabbing; these sensations are usually secondary to cold, pressure, or emotion [8]. Although the exact cause of pain remains unknown, several reports propose impingement of the local nerve fibers after smooth muscle contraction to be causative [8].

Inherited leiomyomas are associated with various syndromes. Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a rare disorder that manifests when Reed’s syndrome is associated with renal cell cancer [9]. Most of the pathogenetic details of sporadic CLs are unknown; however, it is established that piloleiomyomas can originate from any of the attachment points of the arrector pili muscle, proximal to the hair follicle and distal to multiple attachment points within the papillary and reticular dermis and basement membrane zone [10].

Multiple leiomyomas, unlike solitary tumors, can be inherited in an autosomal-dominant fashion with variable penetrance [11].

It has been found that there were heterozygous germline mutations of the Krebs cycle enzyme, fumarate hydratase (FH), in patients with Reed’s syndrome [12]. FH, a constituent enzyme of the Krebs or tricarboxylic acid (TCA) cycle, is known to exist in mitochondrial and cytosolic forms. FH, a constituent enzyme of the Krebs or tricarboxylic acid (TCA) cycle, is known to exist in mitochondrial and cytosolic forms. The mitochondrial variant catalyzes the conversion of fumarate to malate, and since 2002, has been considered a tumor suppressor [13].

If untreated, cutaneous leiomyomas continue to grow, with new lesions appearing over many years [14]. Surgical excision, with or without skin grafts, is the gold standard for cure [15]. Destructive methods such as electrodessication, cryotherapy, or carbon-dioxide laser may be employed for small lesions, but there is little known benefit over excision, and unwanted scarring may occur [16,17]. Leiomyoma associated pain can be managed medically with drugs known to affect smooth muscle contraction, such as nitroglycerine, nifedipine, phenoxybenzamine, and doxazosin; recent reports also suggest the use of calcium channel blockers, botulinum toxin type A injections, antidepressants, and triamcinolone acetonide injections [18,19]. For temperature-induced tenderness, gabapentin and topical analgesics, such as lidocaine or capsaicin, may be used [20,21].