What causes red streaking lines underneath the nail matrix, also known as splinter hemorrhages?

Causes of Red Streaking Lines Underneath the Nail Matrix (Splinter Hemorrhages)

Red streaking lines underneath the nail matrix, known as splinter hemorrhages, are most commonly caused by trauma, but can also indicate serious systemic conditions including infective endocarditis, vasculitis, antiphospholipid syndrome, and dermatological diseases like psoriasis and lichen planus. 1

Primary Etiologies

Traumatic Causes

• Trauma is the single most common cause of splinter hemorrhages, occurring from direct physical injury to the nail bed 1
• Chronic repetitive microtrauma from occupational or daily activities can produce recurrent hemorrhages without obvious injury 2
• Idiopathic atraumatic splinter hemorrhages can occur spontaneously in healthy individuals and may resolve without treatment within 3 months 3

Infectious Causes

• Infective endocarditis remains a critical diagnosis to exclude, as splinter hemorrhages were historically recognized as an important sign of subacute bacterial endocarditis 4
• Secondary bacterial or fungal infections can develop in damaged nail beds, though these typically present with additional findings like nail discoloration and debris accumulation 5

Vascular and Thrombotic Disorders

• Antiphospholipid syndrome causes multiple subungual splinter hemorrhages through a thrombotic mechanism, often occurring concomitantly with arterial thrombotic events at diverse sites 4
• Vasculitis of various etiologies can produce splinter hemorrhages as a manifestation of small vessel inflammation 1
• Raynaud phenomenon and other forms of vascular insufficiency are associated with nail bed changes including hemorrhages 5

Dermatological Conditions

• Psoriasis commonly affects the nail apparatus and can produce splinter hemorrhages along with other nail changes including pitting, onycholysis, and subungual hyperkeratosis 5, 1
• Lichen planus causes nail involvement in approximately 10% of affected patients, with potential for hemorrhages alongside thinning of the nail plate and subungual hyperkeratosis 5, 1

Drug-Induced Causes

• Taxane chemotherapy (docetaxel and paclitaxel) causes subungual hemorrhages as part of a spectrum of nail toxicities, with hemorrhages developing due to direct cytotoxic damage to the nail bed epithelium 5
• The hemorrhages may be accompanied by painful subungual hematomas or abscesses requiring nail plate removal 5
• Other chemotherapeutic agents including capecitabine, etoposide, and anthracyclines can produce similar findings 5, 6
• Photosensitizing drugs (tetracyclines, quinolones, psoralens, retinoids) may contribute to nail bed damage and hemorrhages 6

Clinical Approach

Key Distinguishing Features

• Location matters: Fresh traumatic hemorrhages typically occur in the distal one-third of nails, though chronic recurrent hemorrhages may appear in middle or proximal thirds 2
• Associated symptoms: Fresh lesions may cause burning sharp pain and tenderness lasting several days 2
• Pattern recognition: Multiple fingernail involvement suggests systemic disease rather than isolated trauma 4
• Color evolution: Hemorrhages appear as non-blanchable reddish-brown linear streaks that darken over time 3

Essential Workup Strategy

When splinter hemorrhages are identified, immediately assess for:

• Cardiac evaluation if multiple nails affected or systemic symptoms present (fever, new murmur, constitutional symptoms) to exclude endocarditis 4
• Antiphospholipid antibodies (anticardiolipin antibodies, lupus anticoagulant, anti-β2-glycoprotein I) if thrombotic history or multiple hemorrhages present 4
• Inflammatory markers (ESR, CRP) and vasculitis screening if systemic symptoms suggest autoimmune disease 1
• Medication review for recent initiation of chemotherapy, photosensitizing drugs, or other nail-toxic agents 6
• Dermatological examination for psoriatic plaques, nail pitting, or lichen planus lesions on skin or mucosa 5, 1

Common Pitfalls to Avoid

• Do not dismiss multiple splinter hemorrhages as purely traumatic without excluding serious systemic disease, particularly in patients without clear trauma history 1
• Do not assume fungal infection based solely on nail appearance; splinter hemorrhages are not a primary feature of onychomycosis, which presents with thickening, discoloration, and friable texture 5
• Do not overlook drug-induced causes in patients receiving chemotherapy, as early recognition allows for preventive interventions like cryotherapy with frozen gloves 5
• Recognize that spontaneous resolution can occur in idiopathic cases, avoiding unnecessary interventions in otherwise healthy individuals 3