Differential Diagnosis for the 4-week-old Boy with a Skin Lesion
- Single most likely diagnosis:
- Congenital melanocytic nevus: This is the most likely diagnosis given the presence of a well-demarcated, hyperpigmented patch with coarse terminal hair and a hyperkeratotic, rugose surface. The lesion's characteristics, including its size, texture, and hair growth, are consistent with a congenital melanocytic nevus.
- Other Likely diagnoses:
- Neurofibroma: Although the patient's brother has neurofibromatosis, the description of the lesion does not strongly suggest a neurofibroma. However, it is still a possibility, especially given the family history.
- Congenital hairy nevus: This diagnosis is similar to congenital melanocytic nevus but may not have the same level of pigmentation. The presence of coarse terminal hair within the patch supports this diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Malignant melanoma: Although rare in infants, malignant melanoma can occur and is often associated with large congenital melanocytic nevi. It is essential to monitor the lesion for any changes in size, color, or texture.
- Spinal dysraphism: The presence of a skin lesion with hair can be a sign of an underlying spinal anomaly, such as spina bifida. Imaging studies may be necessary to rule out this possibility.
- Rare diagnoses:
- Becker's nevus: This is a rare condition characterized by a hyperpigmented, hairy patch, often on the chest or shoulder. It is usually seen in males and may be associated with other anomalies.
- Epidermal nevus syndrome: This is a rare condition characterized by the presence of epidermal nevi, which can be associated with other systemic anomalies, including neurological and skeletal abnormalities. The description of the lesion does not strongly suggest this diagnosis, but it is still a possibility.