What is the best course of action for a 1-month-old infant with a persistent, unchanged dark spot on their back, no symptoms of infection or trauma, and a history of ringworm infection, but no other concerning symptoms or comorbidities?

Management of a 1-Month-Old Infant with a Persistent Dark Spot on the Back

For a 1-month-old infant with an asymptomatic, stable dark spot on the back and no concerning features, the appropriate initial step is referral to a pediatric dermatologist or dermatologist with expertise in congenital lesions for proper evaluation, with ultrasound of the spine area of interest as the imaging modality of choice if there is any concern for underlying spinal dysraphism. 1, 2

Initial Clinical Assessment

The key distinction in this case is determining whether this represents a benign skin lesion versus a cutaneous marker of underlying spinal dysraphism:

Features Suggesting Benign Skin Lesion

• Stable appearance (no change in size or color) 1
• Absence of symptoms (no pain, itching, bleeding) 1
• No systemic signs (no fever, weight loss, neurologic deficits) 2

Red Flags for Spinal Dysraphism

You must specifically examine for:

• Location over the midline spine (particularly lumbosacral region) 2
• Associated findings: hairy patch, palpable lump, sacral dimple, asymmetric gluteal cleft 2
• Neurologic deficits: lower extremity weakness, abnormal extremity movements, neurogenic bladder 2

Recommended Diagnostic Approach

If Midline Location with Concerning Features

Ultrasound of the spine area of interest is the appropriate initial imaging modality for infants <4 months of age when skin abnormalities such as discoloration, sacral dimple, or palpable lump are present. 2 This evaluates for signs of spinal dysraphism including tethered cord, syringomyelia, and intraspinal lesions. 2

• Radiography is not useful for initial evaluation of skin abnormalities in this age group 2
• MRI spine without IV contrast or without and with IV contrast is an alternative if ultrasound is inadequate or the infant is >4 months old 2

If Lateral/Off-Midline Location Without Concerning Features

Referral to pediatric dermatology within the first few months of life is appropriate for proper characterization and management planning. 1 This is likely a benign congenital skin lesion such as:

• Congenital dermal melanocytosis (Mongolian spot) - common benign pigmented lesion 3, 4
• Sebaceous nevus - requires dermatologic monitoring 1
• Café-au-lait macule - may warrant evaluation if multiple lesions present 5, 3

Management Plan

Immediate Actions

• Complete physical examination focusing on:
  • Exact location (midline vs. lateral) 2
  • Associated cutaneous findings (hair, dimple, mass) 2
  • Neurologic examination of lower extremities 2
  • Presence of other skin lesions 3, 6

Imaging Decision Algorithm

1. Midline location + any concerning feature → Ultrasound spine area of interest 2
2. Off-midline location + stable appearance → No imaging needed, dermatology referral 1
3. Any neurologic deficit present → Urgent MRI spine (with or without contrast) 2

Follow-Up Protocol

For benign skin lesions after dermatology evaluation:

• Regular clinical monitoring by dermatologist with frequency based on lesion characteristics 1
• Parent education to monitor for rapid growth, bleeding, ulceration, pain, nodule development, or color changes 1
• Serial photographs can help track changes over time 1
• After first year: minimum yearly dermatologist evaluation if no concerning features 1

Critical Pitfalls to Avoid

Do not dismiss midline skin lesions without proper evaluation - up to 50% of children with spinal dysraphism have overlying cutaneous markers. 2 The window for ultrasound evaluation closes around 4 months of age as the posterior elements ossify, necessitating MRI thereafter. 2

Do not perform biopsy without dermatology consultation - if suspicious changes develop, complete excisional biopsy is preferred over shave biopsy for comprehensive histological assessment. 1

The history of ringworm infection is likely unrelated to the current dark spot, as fungal infections typically present with scaling, erythema, and pruritus, none of which are present here. 5, 4