What Is Infantile Digital Fibromatosis?
Infantile digital fibromatosis is a rare condition that causes single or multiple asymptomatic pinkish nodules (benign tumors) along the fingers or toes during early childhood. The first case of infantile digital fibromatosis was reported in 1965 by an Australian pathologist, Douglas Reye. In most cases of this condition, the lesions are present at birth. These lesions are generally painless and suppressed gradually. They usually do not require treatment.
What Causes Infantile Digital Fibromatosis?
The exact cause of infantile digital fibromatosis is unknown. However, the hypothesis states the defects in the organization of the microfilaments of the myofibroblast.
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Myofibroblasts are specialized fibroblast cells (biological cells that help form connective tissue) with contractile activity. The transformation of fibroblasts into myofibroblasts plays a crucial role in wound healing and restoration of tissues. The contractile property of the myofibroblast may be beneficial during the tissue remodeling process (physiological renovation of existing tissues).
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The presence of excessive myofibroblast may be harmful to tissue function, especially during the body's reaction to tumors. Infantile Digital Fibromatosis is thought to be related to any impairment of differentiation and proliferation of myofibroblast cells during tissue repair.
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Literature shows its association with abnormal bone morphogenic protein (BMP) signaling (the group of signaling molecules that comes under the transforming growth factors-β superfamily of proteins) that could stimulate myofibroblast growth.
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Rarely, cases have occurred following trauma.
What Is the Prevalence of Infantile Digital Fibromatosis?
Infantile digital fibromatosis (IDF) is extremely rare, with approximately 250 cases reported worldwide. Cases of infantile digital fibromatosis occur commonly among both males and females. One-third of patients with IDF are congenital that are present from birth or seen during the first year of life. Reports of adult cases are rarely seen.
What Are the Symptoms of Infantile Digital Fibromatosis?
The clinical presentation of infantile digital fibromatosis typically presents as an isolated asymptomatic nodule in the lateral or dorsal aspect of the fingers or toes.
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They appear in light pinkish to dark red color.
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The nodule is firm and less than two centimeters in diameter.
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The larger lesions may limit adjacent joint motion and cause disfigurement.
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Primarily, the lesions develop as an inactive form of tumor and later progress rapidly in the subsequent months. The size remains stable for several months until spontaneous suppression of the lesion.
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These lesions occur in the lateral aspect of the finger and toes except the thumb finger and greater toe.
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In rare cases, lesions of IDF result in deformities or functional impairments. Sometimes, the lesions may erode the adjacent bone.
How Is Infantile Digital Fibromatosis Diagnosed?
The diagnosis of infantile digital fibromatosis is based on the clinical presentation of the lesions in the patients. The symptoms of infantile digital fibromatosis usually begin in the newborn stage or during early childhood. The doctor may perform a procedure called a biopsy or fine needle aspiration. Fine needle aspiration involves removing a tissue sample from the lesion site to investigate them under a microscope. The sample is analyzed by immunofluorescence staining of the filaments. The histopathological findings of infantile digital fibromatosis help confirm the condition's diagnosis.
What Are the Pathological Findings of Infantile Digital Fibromatosis?
Histopathological Findings of dyed stains of infantile digital fibromatosis tissues show unique confirmatory features of the condition.
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Pathological findings of IDF show a small tumor covered by intact epithelium and growth restricted to the middle layer of the skin (dermis).
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As the condition progresses, the findings show a tongue-like extension compressing the superficial layer of the skin.
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The histopathological findings show the appearance of interlacing or twisted spindle cells with abnormal round-to-ovoid granular cytoplasmic inclusions. Inclusion bodies are the specific protein type present in tissue cells.
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The presence of inclusion bodies denotes the accumulation of actin (microfilament bundles) and vimentin (filaments used to mark cancers) and the progression of contractile proteins in the cytoplasm.
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The confirmatory diagnosis of infantile digital fibromatosis is made through small lesions that are centered in the dermal layer of a digit that comprises spindle-shaped cells and expresses smooth muscle actin, calponin (calcium-binding protein associated with actin filament), and desmin (a muscle-specific protein) proteins.
How Is Infantile Digital Fibromatosis Treated?
Initially, infantile digital fibromatosis was believed to be a malignant condition requiring surgical interventions and removal of the affected digit. Later it was proved to be a benign condition that might suppress progressively.
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In asymptomatic conditions, the affected patients are kept under observation. Most lesions disappear themselves and do not require any treatment.
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Surgical interventions are required in these patients for diagnostic purposes.
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Progressive growth of the condition may affect the neurovascular structure (structures involving both nerves and the blood vessels).
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Surgical interventions are suggested for patients with functional impairments, progressive growth, and cosmetic concerns.
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The conservative treatment option depends on the size of the lesion.
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Cases of infantile digital fibromatosis with less than two centimeters are recommended for serial observation and are advised for treatment only when symptomatic.
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Cases with more than two centimeters are advised for conservative treatment options such as intralesional chemotherapies or corticosteroid injections.
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Intralesional treatment options include Triamcinolone injections, glucocorticoid, 5-Fluorouracil, or a chemotherapy drug in the lesions.
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Intralesional injections of 5-Fluorouracil at a dosage of 0.2 mL (milliliters) at 50 mg/dL (milligrams per deciliter) in the lesion site are advised for five months, followed by intralesional Triamcinolone injections at a dose of 0.5 to 2 mL at 10 mg/dL are given for five to forty months.
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Patients with progressively enlarging lesions and highly symptomatic conditions are advised for surgical nodule resection. There is the highest rate of recurrence in patients who underwent surgical interventions.
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The prognosis of the patients with infantile digital fibromatosis is excellent.
Conclusion
Infantile digital fibromatosis is an uncommon benign lesion at the lateral and dorsal aspects of the fingers and toes, except for the thumb and the greater toe. The lesion may develop spontaneously for some time and starts to regress in size. The histopathological findings of the condition have features that distinguish them from other types of fibromas. Most cases are asymptomatic and do not require any treatment. Highly symptomatic patients are recommended for surgical excision of the lesion.
