Diagnosis: Porphyria Cutanea Tarda (PCT)
The clinical presentation of red, itchy skin progressing to bullae formation, rupture with ulceration, and healing with hyperpigmentation in sun-exposed areas is most consistent with Porphyria Cutanea Tarda (PCT), which should be confirmed by elevated serum and urinary porphyrins and uroporphyrinogen decarboxylase (URO-D) deficiency. 1
Clinical Features Confirming PCT
Typical cutaneous lesions include bullae, hyperpigmentation, and erosions specifically at sun-exposed areas such as hands and face, which matches the described progression from red, itchy lesions to bullae formation and subsequent hyperpigmentation 1
The disease is characterized by low activity of URO-D enzyme involved in heme synthesis, with the sporadic form (most common) showing 50% decreased URO-D activity predominantly affecting hepatocytes 1
Pathogenetic co-factors frequently include hepatotropic virus infection (particularly HCV), chronic liver involvement, and altered iron metabolism genes 1
Diagnostic Workup
Diagnosis is definitively ascertained by simple laboratory investigations showing URO-D deficiency and elevated levels of serum and urinary porphyrins 1
Complete the clinical work-up with evaluation of liver involvement, as this is frequently associated with both HCV and PCT 1
Consider screening for HCV infection given the established pathogenetic role, particularly in sporadic PCT cases in certain geographical areas 1
Differential Diagnoses to Exclude
Bullous Pemphigoid
While bullous pemphigoid presents with tense bullae on erythematous skin and can show hyperpigmentation, it typically affects trunk and extremities (not specifically sun-exposed areas), demonstrates linear IgG/C3 deposits on direct immunofluorescence, and occurs predominantly in elderly patients 1, 2
The absence of sun-exposure specificity and the presence of positive Darier's sign would point away from PCT 1
Cutaneous Mastocytosis (Diffuse Form)
DCM can present with blistering and bullae that rupture leaving erosions, with hyperpigmentation persisting into adulthood 1
However, mastocytosis typically presents in early childhood (at birth or early infancy), shows positive Darier's sign (wheal and flare after stroking), and demonstrates increased dermal mast cells on histopathology 1
Necrotizing Fasciitis with Hemorrhagic Bullae
Hemorrhagic bullae can be an early sign of necrotizing fasciitis, most commonly associated with Vibrio species infection (particularly in patients with diabetes) 3
This diagnosis would present with rapid deterioration, systemic toxicity, and requires immediate surgical intervention—distinctly different from the chronic, sun-exposure-related pattern of PCT 3
Treatment Approach
Address underlying pathogenetic co-factors, particularly HCV infection if present, as this may be driving the PCT manifestation 1
Avoid sun exposure to sun-exposed areas (hands, face) where lesions characteristically develop 1
Manage iron metabolism abnormalities through phlebotomy or iron chelation therapy (standard PCT management based on general medical knowledge)
Topical corticosteroids are NOT the primary treatment for PCT, unlike other bullous conditions 1
Critical Pitfalls to Avoid
Do not assume this is simply bullous pemphigoid or another autoimmune blistering disease without checking porphyrin levels and URO-D activity, as the sun-exposure pattern and hyperpigmentation are pathognomonic for PCT 1
Do not delay evaluation for underlying HCV infection or other hepatotropic viruses, as these are frequently associated pathogenetic factors requiring specific management 1
Do not treat with high-dose systemic corticosteroids (as would be appropriate for bullous pemphigoid) without confirming the diagnosis, as PCT requires fundamentally different management targeting porphyrin metabolism 1
Recognize that the hyperpigmentation in PCT is a characteristic feature of the disease process itself, not simply postinflammatory hyperpigmentation requiring separate depigmentation therapy 1, 4, 5